Samsung 2693HM - Doesn't turn on (no standby)

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

The voltage on the big cap looks a bit low. If you have 230V AC at the wall plug, you should get closer to 325V DC on the big cap (though if you have only 220V AC, the voltage on the big cap should be closer to 310-311V DC.)

I can't say for sure, it happens that I did measured wall socket AC voltage before I tested the 'standby' voltage and big fat cap voltage, but I forgot the correct value. I 'think' it was 227v AC.

could you post some pictures of the main/logic board too? There will probably will be at least 2 voltage regulators there (usually 3.3V and 1.8V) that we'll need to check out.

I made some photos of the main/logic board. Please check the attached photos. First 8 images are 'fresh' and last 2 are from back in 2017 (just so we can compare them).

What I noticed and what I tried to 'catch' with my phone camera are those....(kinda) like.... 'flame drawings'. You know, like when you try to draw a 'flame'. I thought 'oh, my main board is burned completely. You'll notice also at the right edge that its not a clear 'white' line but 'dirty yellowish' one. I managed to clean that line with 99% Isoprophyl alcohol. There is also some (I think a guy who assembled/checked the monitor in factory marked it with a pen), 'sign' on the board. I managed to almost clean that as well. Also tried to clean those 'flames' markings and I think they can be 'removed too.

But anyway, I thought board is burned. Then I had an idea to try and check if I have some old photos from back in 2017 of the same board. And...to my surprise board had the same 'flame markings' like it has now. So now I don't know what to think, but you might have an idea what those 'flame markings' mean?

Hi!

Yeah, I'm back. Actually, I never left this place to begin with. With all the nice knowledgeable folks around here, it's hard to do that.

You being one of them.

I actually like it when I see people asking a lot of questions - that means they are actively thinking about the problem, which is good.

Well, I'm glad that you like when you see many questions, but I know that many people don't like it. Just few minutes ago, I got 'slammed' for asking a long question from one guy (at an electronics discord channel) who told me: "write SHORT description of the issue. NOT a long story."

It's not that I like to 'bother' people with my long posts. I just try to provide (from my newbie point of view) all the information that I can. Maybe a value of the information that I provide is very small (or nonexistent) but I still like to provide it nonetheless. From my point of view, it can still 'create an image' of the situation and how I got there.

With good thorough responses, it's also easier for us to figure out what's going on. If anything, I think a lot of other fellow members here will agree that vague topics with vague questions about a problem or not reporting back (and then worse - ignoring or skipping over any suggested advice) tend to waste a lot more time to get to a solution and actually make it harder for us too.

I agree with you. I'm aware that I don't have a knowledge and I know (feel) that I'm at the right place to get directions. I understand that there is a present danger while checking components under high voltage. Thats why I ask so many questions. In electronics you can fix almost everything by changing it for a new part. But I got a no 'spare' life. So I gotta ask many questions.

[momaka]

Re: Samsung 2693HM - Doesn't turn on (no standby)

I made some photos of the main/logic board. Please check the attached photos.

Thanks!
Really good quality photos, by the way. That really helps.

There is a white 3 Amp fuse at the top, below the middle connector.
Check the resistance of this fuse and make sure it is not open-circuit.

Next.... I was wrong about there being only two voltage regulators. This board appears to use several buck regulators instead (as the round SMD inductors on the left side of the board suggest.)

If the 3 Amp fuse mentioned above is OK (i.e. shows good low resistance), then check the voltages (relative to ground) at the positive (+) terminals on the SMD electrolytic caps on the left side seen in the first image of the logic board. The negative (-) terminal on these SMD electrolytic caps is marked with a black semi-circle on top. So the positive (+) terminal is the one opposite to that. Report what voltages you get, starting from the cap at the top left side (it appears that cap is labeled C610 on the PCB.)

Also, check the voltages on the tab and two outer (left and right) pins of IC304 (it's located to the left of the big "main" chip in the middle of the board.)

Lastly, measure the voltage (again, relative to ground) on pin POWER_EN while plugging in the power supply in the wall. (Note: this is the same pin that connectors to PS_ON on the power supply board.) Also, if possible, try to measure the same pin when you press the monitor's power button. Do this test, only if the 3 Amp fuse above tests good, though.

On a separate note, what happens if you disconnect the LVDS connector (the one with the multi-color wires seen on the top-right of this picture) and plug in the monitor. Does the monitor's power LED indicator light still glow as it would normally when the monitor is in standby mode? What about if you disconnect the small connector on the right (again seen in the same picture above) that's for the inverter control. Does that do anything for the power LED indicator? Basically, I want to check if there is some type of feedback circuit in this monitor that prevents the logic board from showing any activity if it doesn't detect certain voltages.

What I noticed and what I tried to 'catch' with my phone camera are those....(kinda) like.... 'flame drawings'. You know, like when you try to draw a 'flame'. I thought 'oh, my main board is burned completely. You'll notice also at the right edge that its not a clear 'white' line but 'dirty yellowish' one. I managed to clean that line with 99% Isoprophyl alcohol.

That's leftover flux from when the board was manufactured (soldered.)
It's nothing to worry about and can be left alone.

You being one of them.

Thanks!
I just try to give back to the community here when I can. I really learned a lot from this place, so it's the least I can do.

Well, I'm glad that you like when you see many questions, but I know that many people don't like it. Just few minutes ago, I got 'slammed' for asking a long question from one guy (at an electronics discord channel) who told me: "write SHORT description of the issue. NOT a long story."

Well, the "double-sided" edge of writing long descriptions is that some people just don't have too much time to read through each thread. So if the thread looks like a "wall of text", I notice that a lot fewer people read through it. However, the advantage is that you do indeed may give a "fuller" picture right from the first time, and that can help get quicker to the solution. So in the end, this may or many not take more time than compared to a thread with a short description, but having to go a lot "back and forth" to get information from the O/P. So to me, it makes more sense to post one "fuller picture" than many smaller ones, but not everyone sees it that way. And admittedly, even I sometimes say to myself, "oh, I'll have a read through that thread later on, because it's too long and I don't have time right now"... and then I sometimes forget to check/read said thread.

I understand that there is a present danger while checking components under high voltage. Thats why I ask so many questions. In electronics you can fix almost everything by changing it for a new part. But I got a no 'spare' life. So I gotta ask many questions.

I understand how you feed about that. The first time I fixed an electronic device, I too took a lot of precautions (had safety glasses on, a fire extinguisher nearby, and etc. ) out of fear that something will come out and "bite me in the face". And quite frankly, there is nothing wrong with that - i.e. being careful. Over time, though, if you do this more often, you will learn what's dangerous and what isn't... and eventually you'll see that the chances of actually dying of electrocution doing something like this are probably less than getting hit by a lightning strike - that is, of course, if you're careful. If you're careless / sloppy, those chances do increase. But even then, it's still probably less dangerous than going out for a drive in your car on the highway.

On that note, I think you may not be familiar with electroBOOM's Youtube channel, but have a look sometimes if you have time. It's comedy and educational... but most importantly shows you what can happen if you get careless or "sloppy" with electronics. He does it on purpose... and that's the funny part. (but he knows what he is doing 100%.)
https://www.youtube.com/channel/UCJ0...0wOKEqT2Z1HEtA

But really, unless you have a heart pace maker or plug something in the wall and happen to get electrocuted in such a way that your body cannot disconnect from the source, then those are really the only cases where electrocution may get fatal. For most other cases, you might just get an unpleasant shock... sort of as a "wake up and be careful" reminder.

On that note, be careful around the big fat cap on your monitor, even after you unplug it from the wall. If the logic board is not working and not drawing power from the PSU, it can take a very long time for that cap to discharge, even after the PSU is unplugged from the wall. So if you happen to touch the (+) and (-) terminals on it with your hands (or paths that lead to those terminals), you may get an unpleasant "sting" to you hand. It's not really dangerous or damaging to your body, but it's certainly unpleasant. So just be mindful of that cap (and the entire primary / high-voltage side of the PSU in general.)

[R_J]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Standby voltage: 5.2v
BIG FAT capacitor voltage: 307v

Have you tried disconnecting the cable between the main board and the power supply to see if you get the other voltages?
With the cable disconnected, the PSON pin should be close to 4~5 volts
These power supplies usually have a pullup resistor to turn on the power supply when the main board is disconnected from it.

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Hey guys. Thanks for your answers.

I kept re-reading your posts, and somehow I have a feeling that you have wrong imporession about something. About how I measured that BIG FAT capacitor, (or any other measure).
So please let me explain it first...

I pulled out bare power board out of the monitor and put it on the table. On the table there were NO OTHER boards present and NO OTHER boards connected to power board. I only attached power cable to power board, and connected the cable to a wall socket. Thats it! No other boards were connected. This is how I tested some elements before this post.

Have you tried disconnecting the cable between the main board and the power supply to see if you get the other voltages?
With the cable disconnected, the PSON pin should be close to 4~5 volts
These power supplies usually have a pullup resistor to turn on the power supply when the main board is disconnected from it.

Thanks R_J for trying to help me!

Ok, so yes, as I said I did NOT have any other board connected to my power board while I was checking that BIG FAT cap (and also a standby voltage on a CNM803 connector of my power board).

BIG FAT cap voltage is checked like this: I put negative probe at capacitor negative leg, and then I touched capacitor's positive leg with postitive probe.
I hope thats correct, because at one discord electronics channel (which some visitors of this topic are also members of), that I should NOT touch with my negative probe a ground while measuring that big fat cap. So I just touched its legs directly (negative probe to negative leg, positive probe to positive leg, and it showed 307v).

So R_J, to answer your question: Yes, since I didn't even had main board connected to power board, while I was testing a big fat cap, these are 'the other voltages' that you asking me to check.

If you want me connect only main board to a power board and put them 'bare' on the table while no other monitor elements are connected (T-CON, inverter, lamps), just these 2 boards (main and power) connected to wall socket, I can do that. But together, I can't do that because its not easy (at least not for me, and aside from that I'm scared if I have to have all things connected while monitor is open and under voltage).

So, can you tell me what kind of checking I should do, I mean what parts should be connected and what can stay disconnected? (sorry that I'm scared this much, but I'm not rushing things before I'm sure what I'm doing)

Thanks!
Really good quality photos, by the way. That really helps.

Hey momaka! Thanks for your answer(s). I took the photos early in the morning while morning light was present. Somehow, everytime I make photos under room light, there are so many reflections. So I tried to make them at daylight this time. There was a struggle again since there were shadows of my hand which was holding a phone, but I did it. As for picture quality, its great if you think that they are clean. When I look at them now, I think I should have blowed the dust, so they could be more clear, since the dust is present a lot. IMO I failed with those photos.

Anyway, I will be honest to you guys. I saw your post(s) one day ago. When I saw so many questions, and when I concluded that (both of) you assumed that I was doing the measurement while other boards were connected together, I was so overwhelmed, that I just read your posts, but then I left, so I can sleep on that, and calm down a bit.

I would try to give answer to most of your questions (but, not today). Today I would have to ask something regarding what you asked me to check. So in this post, you wont have much information to work with. I'm sorry about that guys!
I have to take slower steps. Hope you don't get angry because of my very slow pace with all this.

There is a white 3 Amp fuse at the top, below the middle connector.
Check the resistance of this fuse and make sure it is not open-circuit.

Ok, this is the only question right now that I can give 100% clear answer.

Fuse F601 is not open-circuit (it beeps in multimeter continuity mode)
Fuse F601 resistance is 0.4 Ohm

Resistance between probes of my multimeter is also 0.4 Ohm


btw. I uploaded first 2 images, in case you need to know what are the board markings of specific elments. Do note that on the first picture there are power and main board 'connected'. I just connected them like that so you can visually see it, but they were NOT connected at all while I was measuing standby voltage and big fat cap of the main power board. (only power board was connected throgh the cable to a wall power socket)

Next.... I was wrong about there being only two voltage regulators. This board appears to use several buck regulators instead (as the round SMD inductors on the left side of the board suggest.)

If the 3 Amp fuse mentioned above is OK (i.e. shows good low resistance), then check the voltages (relative to ground) at the positive (+) terminals on the SMD electrolytic caps on the left side seen in the first image of the logic board. The negative (-) terminal on these SMD electrolytic caps is marked with a black semi-circle on top. So the positive (+) terminal is the one opposite to that. Report what voltages you get, starting from the cap at the top left side (it appears that cap is labeled C610 on the PCB.)

One of the questions which got me thinking. I know you will laugh or be pizzed, but for sure there will be some reaction to this question. Because of the way I was checking the voltage of the big fat cap, I had to ask specific question. So I uploaded an image. It's a 3rd image.

I'm asking because when you say 'relative to ground' does that mean that negative probe MUST touch the circle where 'screw' goes (or touch negative part of the board where the measuremnat is happening), OR I can touch negative leg of a capacitor directly with black probe? Its because I was told to NOT touch the ground with negative probe while measuring the voltage of that big cap.

Please check the 3rd image.

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Also, check the voltages on the tab and two outer (left and right) pins of IC304 (it's located to the left of the big "main" chip in the middle of the board.)

Ok, this will sound stuped (like the rest of my questions were 'smart'), but when you say 'tab' what do you mean? On one side of that IC304 there are 3 pins. On the other side there is some wider...'pin'. Is that the one that you refer to as a 'tab'? I will attach a picture regarding that IC304, please check it out and let me know if I guessed correctly? Also, if I was right about positions, can you tell me how you measure it?
If I can guess, while main board receives a power though power board, I should put black probe on a 'tab' and red probe on left pin, and check the voltage? (then keep the negative probe on 'tab' and touch the right pin with red probe). Correct?
I know question is stuped but I just want to make sure we both observe that IC304 from the same angle (point of view).

Please check the 1st attached image in this post.

Lastly, measure the voltage (again, relative to ground) on pin POWER_EN while plugging in the power supply in the wall. (Note: this is the same pin that connectors to PS_ON on the power supply board.)

Hmm, at first I thought I understand what you asked me to do. But the more I think (and I must do that), the more I'm not sure if you assume something that I don't.

First I would measure it in a way that I would put black probe on a GND pin, and touch the POWER_EN pin with a red probe, correct? And I was just about to do that, but then I thought...

I was told that standby voltage should be present at powerboard connector pin, and only then, it will be able (once its shorted to the PS_ON) to provide voltages to other boards which are connected to a power board. Now I'm thinking.... my monitor is disassembled. If I don't touch (press) monitor power button, how can then the voltage be sent to other boards of the monitor? I guess when I press power button on a monitor, it short 'standby' pin with PS_ON pin and then voltage is 'sent' to main(logic) board? Did you assumed that all other monitor parts are all connected together so that I can check voltage on POWER_EN pin? They are not connected...
I know I'm making things complicated and I'm really sorry about that.


Anyway, I attached the image, and that is how I would test the voltage of the POWER_EN pin. Please let me know (if you still have a strength to write answers on my stupid questions) is that 'ok' way? And let me know about what needs to be done so that pin POWER_EN gets the voltage? (what parts needs to be connected? only main board and power board, or should I 'short' some pins in order to make POWER_EN gets its voltage)

Please check the 2nd attached image in this post.

Also, if possible, try to measure the same pin when you press the monitor's power button. Do this test, only if the 3 Amp fuse above tests good, though.

Ouch! Of all requests, this will be hard to do. And I'm freaking scared to do it.
I'll try to explain why....
My monitor doesn't have a 'button' it has 'sensitive touch' area (in the bottom-right corner). In ordter to turn on the monitor (so it can show the picture), you have to touch it. Now, my monitor is disassembled right now. When a monitor looking face down on the table, on the left side there is an inverter board. On the top side there is a T-CON board. Now in the middle, there is a (kinda cradle). Inside that cradle are fixed, but face down, both power board and logic (main) board. I can't do things that you ask me, because it is not accessible to me when the board is in that position (face down on the table, while main and power board are also faced down).

And (maybe it will be funny to read, but I still write it)... I know there are coouple thousand volts present that CCFL lamps use. I'm scared shitless to have all the monitor parts connected and open like that, to mess around with it.

On a separate note, what happens if you disconnect the LVDS connector (the one with the multi-color wires seen on the top-right of this picture) and plug in the monitor. Does the monitor's power LED indicator light still glow as it would normally when the monitor is in standby mode?

If I just disconnect this LVDS (multi-color wired) connector, and assemble back my whole monitor (and put plastic back on it), can I test it that way? (as I said, I'm scared to have this open and under full vontage(s) everywhere). So, can I test it with just that LVDS connector disconnected, but monitor assembled?

That multi-color wired connector goes to T-CON board, correct?

What about if you disconnect the small connector on the right (again seen in the same picture above) that's for the inverter control. Does that do anything for the power LED indicator? Basically, I want to check if there is some type of feedback circuit in this monitor that prevents the logic board from showing any activity if it doesn't detect certain voltages.

Hmm, you say 'small connector on the RIGHT'. On that picture that you used to point me that 'multi-color wired LDVS connector', there is no 'small connector on the right'.(maybe you were looking at different photo?). I would guess you mean the connector on the top (on far left). Right? On that picture multi-color LVDS connecitor is on far right (while the wide white-wired connector is between small one and LVDS connectors). Do you mean that 'small connector' on far left (on the top of the board)?

(I attached the image in previous post (its a first attached image) with connector markings, so you can reffer to them if you want)

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

I understand how you feed about that. The first time I fixed an electronic device, I too took a lot of precautions (had safety glasses on, a fire extinguisher nearby, and etc. ) out of fear that something will come out and "bite me in the face". And quite frankly, there is nothing wrong with that - i.e. being careful. Over time, though, if you do this more often, you will learn what's dangerous and what isn't... and eventually you'll see that the chances of actually dying of electrocution doing something like this are probably less than getting hit by a lightning strike - that is, of course, if you're careful. If you're careless / sloppy, those chances do increase. But even then, it's still probably less dangerous than going out for a drive in your car on the highway.

I'm glad that you understand how I feel. I know its 'easy' later when you know things. And I know how I felt 20 years ago when I was made to change my PC motherboard, GPU, ram parts. I was like... 'oh no, I don't know that, I'll damage something'. Now its ok. But at that first time, I thought I'll brake something, or make certain components faulty, because I didn't knew how to do it. But I was guided and I did it.

Now...the difference here is that...if I do something the wrong way with all this voltages around... tomorrow there wont be anyone comming here to write you guys all these 'nice' long posts. If you know what I mean, and I'm sure you do.

On that note, I think you may not be familiar with electroBOOM's Youtube channel, but have a look sometimes if you have time. It's comedy and educational... but most importantly shows you what can happen if you get careless or "sloppy" with electronics. He does it on purpose... and that's the funny part. (but he knows what he is doing 100%.)
https://www.youtube.com/channel/UCJ0...0wOKEqT2Z1HEtA

I didn't checked it now. I'm so tired of creating these 3 connected posts, but I think I checked his YT clips in the past. After I saw all the sh1t that he is doing, I was like 'this one is insane, lets move on'.

But really, unless you have a heart pace maker or plug something in the wall and happen to get electrocuted in such a way that your body cannot disconnect from the source, then those are really the only cases where electrocution may get fatal. For most other cases, you might just get an unpleasant shock... sort of as a "wake up and be careful" reminder.

About 1-2 years ago... I had an Asus power adapter. I measured the voltage and it didn't gave the voltages that it should. So I watched a YT clip how to open it (by pouring some 'gas' on the edge where the parts were glued together). Ofcorse, in my case nothing went 'easy' as it was on that guy YT clip. So anyway, I ended up finally disassembling it. Just wanted to see the inside of the dmn thing. Now most of the parts on that small power adapter board had that 'white' ...('sh1t'?) thing over most soldered elements. So I decided to remove them. It was a long process because they refused to be removed easily. I knew that I should be careful of those electrolytic caps, so I wasn't touching that. But at one momment, somehow, I guess I touched contact that lead to those small caps, and that fcking sh1t feeling went through my whole body. I felt....I don't know what word would best describe it. I remember that I went to my neighbour and told him what I did and what happen. He started laughing, and said 'its nothing, it will pass, its good to get electrocuted from time to time'. After he said that last part, I was like '....of all the neighbours that I could talk about what happened, I just picked a joker'

So...if that small electrolytic cap produced such feeling, I don't want to get another shock from more serius caps or anything that can electrocute me. So I HAVE TO ASK so many questions. I know it's boring for you guys, and I know you may give up on trying to help me, but I just have to ask, so I can be safe. As I said, I got only one life. No spare parts here.

On that note, be careful around the big fat cap on your monitor, even after you unplug it from the wall. If the logic board is not working and not drawing power from the PSU, it can take a very long time for that cap to discharge, even after the PSU is unplugged from the wall. So if you happen to touch the (+) and (-) terminals on it with your hands (or paths that lead to those terminals), you may get an unpleasant "sting" to you hand. It's not really dangerous or damaging to your body, but it's certainly unpleasant. So just be mindful of that cap (and the entire primary / high-voltage side of the PSU in general.)

Now, don't hold me onto my word, BUT... I think that I tried to measure the voltage of the BIG FAT cap once when the power cable was pulled out from a wall socket. And I think it had almost no voltage (or no voltage at all). That was strange to me since I read so many times that caps can hold charges for so long (even for years).

(If someone is getting some ideas, I'll repeat: ONLY power board was connected through a power cable to a wall socket, and no other boards (sources) were connected, so I don't know what made that cap discharge so fast. And no, I didn't shorted its legs, if thats what you're thinking).


Ok, time to finally finish my posts. The original post was so big that I had to split it in 3 parts.


^
There... I started creating these posts 4-5 hours ago. I'm sure a lot of people would say that I'm crazy (maybe they are correct) for creating such a big posts, especially if I didn't answer clearly most of your questions with measured values.
It took me some time to make a new photos and edit them in photoshop so that I can reffer to them while trying to explain what bothers me about some questions.

Thanks for reading my posts and sorry for creating them as a novel.

[momaka]

Re: Samsung 2693HM - Doesn't turn on (no standby)

BIG FAT cap voltage is checked like this: I put negative probe at capacitor negative leg, and then I touched capacitor's positive leg with postitive probe.
I hope thats correct, because at one discord electronics channel (which some visitors of this topic are also members of), that I should NOT touch with my negative probe a ground while measuring that big fat cap. So I just touched its legs directly (negative probe to negative leg, positive probe to positive leg, and it showed 307v).

Yes, that advice is correct.

The reason why you want to measure across that big cap directly (i.e. put red probe on + and black probe on - ) is because this cap is located on the primary side of the power supply. The primary side is the one directly connected to the mains / wall, so the negative (-) lead of that big cap is NOT connected to regular ground. Instead, the (-) lead of that cap is said to be connected to hot ground - i.e. a ground that is only used for reference on the primary side. On that note, the primary side is also sometimes called the hot side (because that's the side that can burn / electrocute you if you touch anything there with bare hands.)

Conversely, the secondary side of the power supply is the one that is isolated from the primary side... and is also sometimes called the cold side. You can touch anything on the secondary/cold side with your bare hands and nothing will shock you (provided that the power supply doesn't generate any hazardous high voltages on the secondary side, which most monitor PSUs don't... except for the inverter board that powers the CCFLs - although the inverter is usually part of the secondary side, the voltage on the output of the inverter transformers is typically 700-1000V AC.)

So how to distinguish the primary/hot side and the secondary/cold side? Have a look at this picture of your PSU board:
https://www.badcaps.net/forum/attach...7&d=1603854014
You can see on the lower left side of the PSU where there is a thick white line drawn on top of the PCB, with the words "HOT" and "COLD" on both side. This line essentially tells you which components are on the primary side and which are on the secondary side.

So knowing that... when we ask you to do any voltage measurements on the primary side, you should put your multimeter's black probe on the big fat cap's negative (-) lead and then use the red lead to measure whatever voltage it is that is needed.
On the other hand, when we ask you to measure any voltage on the secondary/cold side, you should put your multimeter's black probe either on the monitor's metal chassis (but only if the PSU or board you are measuring is installed in the metal chassis) *OR* put the multimeter's black probe on a metal ring around any of the screw holes on the PCB. Both of these are connected to secondary side ground (which by the way is also sometimes called earth.)

I took the photos early in the morning while morning light was present. Somehow, everytime I make photos under room light, there are so many reflections.

Ah, that explains the good images.
You just can't beat natural light! At least that's the conclusions I have come to as well, whenever I take pictures to upload here. If I take them with flash with non-natural light, they never look as good.

I have to take slower steps. Hope you don't get angry because of my very slow pace with all this.

No worries at all. This is your monitor, so feel free to go as slow or as fast as you like.
(Of course if you put this away for a year and then come back to it again, chances are both you and us would have forgotten what was tested. And with that, it may take some time again before we go through the entire thread to read all the responses and what was tested and where we last left off.)

Fuse F601 is not open-circuit (it beeps in multimeter continuity mode)
Fuse F601 resistance is 0.4 Ohm

Good.

btw. I uploaded first 2 images, in case you need to know what are the board markings of specific elments.

Thanks! That's actually going to be very helpful both to you and to us if we refer to any voltages on any connectors/pins.

Do note that on the first picture there are power and main board 'connected'. I just connected them like that so you can visually see it, but they were NOT connected at all while I was measuing standby voltage and big fat cap of the main power board.

Got it.

It shouldn't make a difference for the big cap, but it can for the Standby voltage (for example, if the standby rail is shorted on the main board, it can make it seem as if the PSU board is not outputting any standby... which may still be the case, though we will see once you measure the voltages at those caps that I asked about in my previous post - i.e. the voltage at C610, C619... and etc. that you listed in the 2nd image of your first reply.)

So I uploaded an image. It's a 3rd image.

I'm asking because when you say 'relative to ground' does that mean that negative probe MUST touch the circle where 'screw' goes (or touch negative part of the board where the measuremnat is happening), OR I can touch negative leg of a capacitor directly with black probe? Its because I was told to NOT touch the ground with negative probe while measuring the voltage of that big cap.

Good question.

The answer is that both option 1 and option 2 are correct.
In particular, option 1 is very good because then you know exactly what the voltage is across the cap. However, trying to measure across each cap like shown in option 1 can be cumbersome. This is where option 2 is easier.

As for option 3... I'm not quite sure what that little square connects to on that PCB, but it could be an isolated point not connected to anything. If that's the case, then you won't get any voltages, so I suggest to NOT use option 3.

And finally, there is a 4th option: if your PSU and/or logic board are installed *and* bolted to the metal chassis of the monitor, then you can use the metal chassis of the monitor as a ground point too (i.e. connect your black multimeter probe there.)

What I personally like to do is I like to get an alligator clip and connected my multimeter's black (-) probe either to the metal chassis (4th option suggested above) or clip the alligator clip to one of those round screw hole rings. That way, I can measure voltages with just one hand, while I can use the other hand to either press buttons on the monitor or keep that hand on the On/Off button on my surge protector / extension cord, in case I need to turn off power quickly.

but when you say 'tab' what do you mean? On one side of that IC304 there are 3 pins. On the other side there is some wider...'pin'. Is that the one that you refer to as a 'tab'?

Yes!
That wider pin would be the "tab".

I will attach a picture regarding that IC304, please check it out and let me know if I guessed correctly? Also, if I was right about positions, can you tell me how you measure it?

Connect black (-) multimeter probe to ground (i.e. chassis or on a ring for a screw hole on the PCB) and then take voltage measurement with red (+) multimeter probe first at position #2, then tab, then position #1. (Note that the tab is also tied to the middle pin on the row of 3 pins, but I prefer and always suggest to use the tab, because it's easier to place the multimeter probe there and you're less likely to slip and short across the IC pins.)

I used your picture here as a reference to where positions #1 and #2 are:
https://www.badcaps.net/forum/attach...7&d=1604276645

[momaka]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Hmm, at first I thought I understand what you asked me to do. But the more I think (and I must do that), the more I'm not sure if you assume something that I don't.

First I would measure it in a way that I would put black probe on a GND pin, and touch the POWER_EN pin with a red probe, correct? And I was just about to do that, but then I thought...

Yes, this is correct.

Connect black multimeter probe to ground in a way that you don't have to hold it with your hand.

After that, put red probe on POWER_EN (or pin PS_ON on connector CNM803 on the power board - both of these are the same thing) and check voltage while PSU is still disconnected from the wall. Now, plug power supply in the wall while still measuring the voltage @ POWER_EN and see what voltage your multimeter shows for the next 3-5 seconds.

I was told that standby voltage should be present at powerboard connector pin, and only then, it will be able (once its shorted to the PS_ON) to provide voltages to other boards which are connected to a power board. Now I'm thinking.... my monitor is disassembled. If I don't touch (press) monitor power button, how can then the voltage be sent to other boards of the monitor? I guess when I press power button on a monitor, it short 'standby' pin with PS_ON pin and then voltage is 'sent' to main(logic) board? Did you assumed that all other monitor parts are all connected together so that I can check voltage on POWER_EN pin? They are not connected...

So when you try to measure POWER_EN / PS_ON, you should have, at a minimum, the PSU board connected to the logic board.

The way it works is that PSU board generates 5V standby on pin ST_BY (on connector CNM803). This 5V standby voltage powers the logic board in standby / soft-off mode (and on the logic board, ST_BY is connected to 5V_MICOM on connector CN600.) When you press the power button on the monitor, the logic board interprets that and sends a signal on pin POWER_EN of CN600 (which goes to PS_ON pin on the power supply board on connector CNM803.) The power board "reads" the POWER_EN / PS_ON signal and turns On the rest of the voltages - i.e. 18V, 5V, and whatever other voltages there are.

Depending on implementation / design, typically POWER_EN / PS_ON either has to be pulled high (to 5V) or low (to 0V or grounded) to make the power supply board turn On. From what I have seen, most monitors use an active high signal to turn On the PSU (meaning you have to feed 5V into PS_ON pin to turn on the monitor.)

But in the above case with the voltage measurement at PS_ON / POWER_EN, I'm trying to have you do that so we can determine if the monitor is trying to turn On or not and also to confirm if PS_ON is active high or not... though I would guess that it is.)

Anyway, I attached the image, and that is how I would test the voltage of the POWER_EN pin. Please let me know (if you still have a strength to write answers on my stupid questions) is that 'ok' way

Yes, that way is OK.
But again, if you don't want to hold black multimeter probe, you can just clip it to any secondary side ground (i.e. metal ring around a hole on the PCB or metal chassis of the monitor.)

And let me know about what needs to be done so that pin POWER_EN gets the voltage? (what parts needs to be connected? only main board and power board, or should I 'short' some pins in order to make POWER_EN gets its voltage)

Just main board and power board will do fine.
If you want / can, maybe also the small board that has the monitor's On/Off button (and then maybe even try pressing it while measuring the voltage to see if PS_ON changes or not.)

Ouch! Of all requests, this will be hard to do. And I'm freaking scared to do it.
I'll try to explain why....
My monitor doesn't have a 'button' it has 'sensitive touch' area (in the bottom-right corner). In ordter to turn on the monitor (so it can show the picture), you have to touch it. Now, my monitor is disassembled right now. When a monitor looking face down on the table, on the left side there is an inverter board. On the top side there is a T-CON board. Now in the middle, there is a (kinda cradle). Inside that cradle are fixed, but face down, both power board and logic (main) board. I can't do things that you ask me, because it is not accessible to me when the board is in that position (face down on the table, while main and power board are also faced down).

I know what you mean. I serviced a Westinghouse monitor not too long ago that had the same "touch" buttons on one side and made it really hard to measure voltages while trying to press the power button.

However, since you don't need to connect the inverter board or the T-con board, can you still have the PSU and main board connected together while also connected to the button board?

If not, perhaps consider soldering a long wire to the PS_ON pin (or POWER_EN pin) and then run that to the side of the monitor. Now you should be able to place the power and logic boards back in the monitor but still be able to measure PS_ON pin while pressing the button.

I know it seems complicated, but if you have some alligator leads, you could pretty much do this hands-free. Then it's just a matter of plugging in the monitor to the wall with one hand and using the other hand to press the power button.

And (maybe it will be funny to read, but I still write it)... I know there are coouple thousand volts present that CCFL lamps use. I'm scared shitless to have all the monitor parts connected and open like that, to mess around with it.

Well, if you don't connect power to the inverter board, then the inverter won't generate those high voltages.

Also, even if the inverter is connected... remember that electricity likes the shortest / easiest path to ground. As long as the CCFLs are connected to the inverter and more importantly, as long as you don't touch the inverter and CCFL cables directly with your hands, that high voltage will NOT jump out to get you. Even if it wanted to, the metal chassis of the monitor is much closer and easier to get to. So you'd have to do something deliberately silly to get shocked from the inverter (as in, be holding the inverter transformers while powering on the monitor.)

If I just disconnect this LVDS (multi-color wired) connector, and assemble back my whole monitor (and put plastic back on it), can I test it that way?

Yes.
The LVDS simply puts the picture on the screen. With the LVDS disconnected, your monitor can still power on and respond to wake-up commands from video input, but the screen will just we white (if the inverter and CCFLs are connected, of course) or nothing if inverter/CCFLs are disconnected.

That multi-color wired connector goes to T-CON board, correct?

Yes.

Hmm, you say 'small connector on the RIGHT'. On that picture that you used to point me that 'multi-color wired LDVS connector', there is no 'small connector on the right'.

Ooops. Yes, I meant small connector on the left. CN601
My brain was thinking left, but my fingers typed "right" for some reason (and they were wrong. )

[momaka]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Now...the difference here is that...if I do something the wrong way with all this voltages around... tomorrow there wont be anyone comming here to write you guys all these 'nice' long posts.

Nah, like I said, you'd have to be quite reckless / careless to die from something like that... and so far, you just don't seem to fit that stereotype, if I may say.

I didn't checked it now. I'm so tired of creating these 3 connected posts, but I think I checked his YT clips in the past. After I saw all the sh1t that he is doing, I was like 'this one is insane, lets move on'.

That's what I thought too the first time around.
But in fact, he is not crazy and knows what he is doing 100% - including the shocks he gets (he knows what can and cannot kill him.)

On that note, these two are probably one of his best videos on the matter of getting shocked:
https://www.youtube.com/watch?v=DOMs7mYm_zs
https://www.youtube.com/watch?v=XDf2nhfxVzg

About 1-2 years ago... I had an Asus power adapter. I measured the voltage and it didn't gave the voltages that it should.... I knew that I should be careful of those electrolytic caps, so I wasn't touching that. But at one momment, somehow, I guess I touched contact that lead to those small caps, and that fcking sh1t feeling went through my whole body.

That's a familiar situation.

In my case, I was working on a TV board that had a short-circuit on one of its outputs. Because of that, the protection kicked in and PSU turned off. However, that PSU had no discharge resistor across its primary cap. So when I opened it and started touching / probing around, I got a nice sting across my fingers when I must have touched some parts across the primary side.

So if I had to guess anything about your power adapter, most likely the output power cord was shorted, making the adapter go into short-circuit protection and turning off its output completely... thus leaving the primary cap completely charged. Either that, or current sense resistor on main switching MOSFET on primary was blown, leaving no path for the big primary cap to discharge through.

So when you touched the small cap, it probably was in some way connected to the primary side and primary cap, and that's how you got the shock.

I remember that I went to my neighbour and told him what I did and what happen. He started laughing, and said 'its nothing, it will pass, its good to get electrocuted from time to time'. After he said that last part, I was like '....of all the neighbours that I could talk about what happened, I just picked a joker'

And here you are now, talking to another joker (i.e. me.)
If I was there with your neighbor, I would probably have nodded in agreement when he said that.

So...if that small electrolytic cap produced such feeling, I don't want to get another shock from more serius caps or anything that can electrocute me.

No, that shock definitely wasn't from a small cap only. Must have touched the primary cap in some way.

And believe it or not, it doesn't get that much worse from bigger caps, as long as voltage is still the same... unless of course you really are dealing with some huge caps (i.e. something you'd see in industrial equipment.)

Now, don't hold me onto my word, BUT... I think that I tried to measure the voltage of the BIG FAT cap once when the power cable was pulled out from a wall socket. And I think it had almost no voltage (or no voltage at all). That was strange to me since I read so many times that caps can hold charges for so long (even for years).

That's because there is a discharge path, and that would be the ST_BY rail.
When you unplug the PSU from the wall, it will continue to supply power on ST_BY to the logic board until the primary cap gets drained... which will usually take anywhere from a second or two to maybe 10-20 seconds max (varies by PSU design and power consumption on the standby rail.) After that, the primary cap may have just a few tens of Volts, and should discharge fairly quickly to just a few volts or less within a few seconds.

Ok, time to finally finish my posts. The original post was so big that I had to split it in 3 parts.

10k character limit?

That's one of my long-time adversaries on here. I get hit by it all the time.

[RJARRRPCGP]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Hello everyone!

I'll try not to create big posts this time (though I'm sure I'll fail).

Ok, here we go...


Back in 2017. one capacitor on my monitor power board failed, so I had to replace it. I decided to change all the caps (except the BIG one), and everything was working well. I had a big help from other members, especially from momaka. He had enough patience to give answer to all my questions.

For those interested in reading that topic, here it is: [help required] which capacitor type for monitor power board

Ok, so, 2 weeks ago... guys from cable company came in, to install cable tv and cable internet connection. For watching TV they used STB device (with card slot) and connected it to my monitor through HDMI cable. It was later that day when I check the TV channels, and then turned the STB device off using a remote control. After I turned it off the STB device had only red standby light.
Next morning, I turned on my pc (and ofc my monitor). I wasn't touching STB device (it still had red standby light). I went out of my room for 10 min, and when I came back, my whole room had a hard smell of burned out electronic. I looked in direction of my monitor and I noticed its turned off. I tried to switch it back but nothing happen.Not even a standby light of my monitor turned on. Nothing!

Sounds a lot like a short, if not a short to the chassis. It could be as simple as a solder joint touching something else that's conductive.

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Thanks momaka for your reply!

I read it couple of times. And I will re-read it again. Right now, I'll only respond to the first of your 3-chain posts, since I'll need to study more your 2nd post.

I understood the explanations from your first post, so here are some results:
(please check any of 3 attached images. 3rd one gives IMO best presentation, since I spent some time making it in photosohp)

Voltages on the capacitors on the left side of the main (logic) board:
-----
C610 = 17.88v
C619 = 17.50v
C3045 = 1.073v
C621 = 1.587v


IC304:
-------
pin 1 = 5.225v
pin 2 = 0v
pin 3 = 5.223v

btw. after I pulled the plug that was connected to a power board, I checked the voltage of BIG FAT and it was already around 6v and dropping (I didn't checked instantly, but after a min or two). Then I checked the other caps on main (logic) board and out of 4 mentioned ^ above, only C619 had around 2.1v very slowly dropping. When I checked BIG FAT cap again, it had around 1.11v and dropping. Then I checked again C619 on main (logic) board and it had around 2.19v (and pretty stable, like it is in no rush to discharge). By now (3 hours later) I guess it discharged probably. Power board and main (logic) board were connected all the time, except that I pulled the plug that was attached to power board.

Also, I got a s*rvice manual for my monitor that I got from back in 2017 when I had issue with caps. So if you don't have it and want to check it out, let me know. I'll upload it. I wasn't sure if it's allowed to upload it, so I decided not to, for now.

So how to distinguish the primary/hot side and the secondary/cold side? Have a look at this picture of your PSU board:
https://www.badcaps.net/forum/attach...7&d=1603854014
You can see on the lower left side of the PSU where there is a thick white line drawn on top of the PCB, with the words "HOT" and "COLD" on both side. This line essentially tells you which components are on the primary side and which are on the secondary side.

So knowing that... when we ask you to do any voltage measurements on the primary side, you should put your multimeter's black probe on the big fat cap's negative (-) lead and then use the red lead to measure whatever voltage it is that is needed.

Ok, I got it. Just one more question: Does that mean, that IF you ask me to measure a voltage of some other element on PRIMARY side, I would again touch negative leg of that BIG FAT cap and use my red (positive) probe to touch the positive leg of any other element that you ask me to measure its voltage? I'm asking if the black probe of my multimeter needs to be ALWAYS touching ONLY a negative leg of BIG FAT cap with black multimeter probe, while I would 'move' my red positive probe to a positive leg of any other elment inside PRIMARY area?

On the other hand, when we ask you to measure any voltage on the secondary/cold side, you should put your multimeter's black probe either on the monitor's metal chassis (but only if the PSU or board you are measuring is installed in the metal chassis) *OR* put the multimeter's black probe on a metal ring around any of the screw holes on the PCB. Both of these are connected to secondary side ground (which by the way is also sometimes called earth.)

Thanks!
Ok, but what about other boards connected to power board? Like main (logic) board? There are voltages which only comes from SECONDARY side of that transformer (located power board), so I would say that any element on main (logic) board can be measured by putting black multimeter probe to a screw rings hole? No danger there (for me or any element located on main-logic board). Correct?

What abotu T-CON board? If 3 boards (power-main-TCON) are connected together, I guess all voltages present on TCON board comming from SECONDARY tranformer side, so I can touch screw-hole ring with my negative probe? Right?

And... what about inverter board? I has those small tranformers. And you said it has 700-1000v. That scares me so much. You said don't touch tranformers there. But...maybe I check voltages (for instance) on on capacitors (on inverter board) but touching screw-hole rings with negative probe, while using positive (red) probe to touch positive leg of a capacitor on inverter board)? Or I MUST touch negative capacitor leg directly with multimeter black probe? I'm asking because of those 700-1000v that you mantioned.
Its not like I"m going to do it, anyway, since my hands were shaking even when I was mesuring those small voltages I posted at the start of this post. But, I'm just asking so I can understand monitor parts better.

No worries at all. This is your monitor, so feel free to go as slow or as fast as you like.
(Of course if you put this away for a year and then come back to it again, chances are both you and us would have forgotten what was tested. And with that, it may take some time again before we go through the entire thread to read all the responses and what was tested and where we last left off.)

Thanks! I'm trying to be as fast as I can, while I'm doing my best to be as slow as I can. ...if this even make sense. In other words, I'll do it as fast as possible, but not before I understand everything I need, or what I think that I need to know). Sometimes, my mind is overwhelmed by the informations I receive. Sometimes, some requests may seam complicated to me, so... sometimes I put things on hold. Later, I'm kinda embarrassed to come back and ask more questions because I fear people would say 'where were you all this time? Do you want us to read all your multiple posts again?'.
So, I'm trying not to get in such situation... but time will show if I failed or not.

What I personally like to do is I like to get an alligator clip and connected my multimeter's black (-) probe either to the metal chassis (4th option suggested above) or clip the alligator clip to one of those round screw hole rings. That way, I can measure voltages with just one hand, while I can use the other hand to either press buttons on the monitor or keep that hand on the On/Off button on my surge protector / extension cord, in case I need to turn off power quickly.

3 questions here:

1st:
I don't have aligator clips. Do I have to buy the one pair of multimeter cables that I can use instead of my regular probes?

2nd:
Can I just buy (make) a wired cable that can have on both ends aligator clips, so one end will 'grab' the negative probe of my multimeter, and the other end will 'byte' the scew-hole ring?

3rd:
since my monitor has that..'touch sensor' (or whats it called) and not regular button', if I manage somehow to pull out that small board which is used to power on my monitor when I touch the bottom-right corner on my monitor.... and when I have that small board 'out'....connected to a main (logic) board.... is there a chance I get shocked once I press the button (make short) so that I give a 'command' to a logic board to turn on the monitor? (I don't even know if that small board as a classic button, since its a touch sensor)



Thats it for now. This was the resond to only 1st of your 3-chain posts.

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Hmm, at first I thought I understand what you asked me to do. But the more I think (and I must do that), the more I'm not sure if you assume something that I don't.

First I would measure it in a way that I would put black probe on a GND pin, and touch the POWER_EN pin with a red probe, correct? And I was just about to do that, but then I thought...

Yes, this is correct.

Connect black multimeter probe to ground in a way that you don't have to hold it with your hand.

After that, put red probe on POWER_EN (or pin PS_ON on connector CNM803 on the power board - both of these are the same thing) and check voltage while PSU is still disconnected from the wall. Now, plug power supply in the wall while still measuring the voltage @ POWER_EN and see what voltage your multimeter shows for the next 3-5 seconds.

I was told that standby voltage should be present at powerboard connector pin, and only then, it will be able (once its shorted to the PS_ON) to provide voltages to other boards which are connected to a power board. Now I'm thinking.... my monitor is disassembled. If I don't touch (press) monitor power button, how can then the voltage be sent to other boards of the monitor? I guess when I press power button on a monitor, it short 'standby' pin with PS_ON pin and then voltage is 'sent' to main(logic) board? Did you assumed that all other monitor parts are all connected together so that I can check voltage on POWER_EN pin? They are not connected...

So when you try to measure POWER_EN / PS_ON, you should have, at a minimum, the PSU board connected to the logic board.

The way it works is that PSU board generates 5V standby on pin ST_BY (on connector CNM803). This 5V standby voltage powers the logic board in standby / soft-off mode (and on the logic board, ST_BY is connected to 5V_MICOM on connector CN600.) When you press the power button on the monitor, the logic board interprets that and sends a signal on pin POWER_EN of CN600 (which goes to PS_ON pin on the power supply board on connector CNM803.) The power board "reads" the POWER_EN / PS_ON signal and turns On the rest of the voltages - i.e. 18V, 5V, and whatever other voltages there are.

Depending on implementation / design, typically POWER_EN / PS_ON either has to be pulled high (to 5V) or low (to 0V or grounded) to make the power supply board turn On. From what I have seen, most monitors use an active high signal to turn On the PSU (meaning you have to feed 5V into PS_ON pin to turn on the monitor.)

But in the above case with the voltage measurement at PS_ON / POWER_EN, I'm trying to have you do that so we can determine if the monitor is trying to turn On or not and also to confirm if PS_ON is active high or not... though I would guess that it is.)

Momaka, thank you for a detailed explanation! I think I (finally) understood your instructions and I finished checking voltages at POWER_EN pin (of main/logic board), that you asked me to measure.

First, here is how I did it (picture #2 in this post shows visually how I connected everything).

- I soldered (red) wire to a POWER_EN pin on the main (logic) board. The other end of that (red) wire was connnected to RED probe of my multimeter.
- I soldered (blue) wire to a GND pin on the main (logic) board. The other end of that (blue) wire was connected to a BLACK probe of my multimeter.
- I separated a whole monitor frame from a monitor (so the small 'power on/off sensor board was still on the frame). Then I connected that small power on/off sensor baord to a main (logic) board using its small 4 pin cable.
- I connected a power board main power cable to an extension cable (extension cable has a ON/OFF switch).

When everything was connected, I turned on the multimeter, and then did it in 3 steps:

1st step: (extension cable On/Off switch was in OFF positoin). Voltage that was measured at POWER_EN pin was 0v (zero volts).

2nd step: (extension cable On/Off switch was in ON position). When I pressed the ON switch on the extension cable, voltage started increasing in in next ~2sec reached 1.217v, and started increasing. After 10 seconds from the moment when I pressed the ON switch on the extension cable, it reached its max of 1.236v. Then started slowly dropping. 18sec after I pressed the ON switch on my extension cable, voltage dropped to 1.213v.

3rd step: (extension cable switch turned ON, monitor turn ON touch sensor was 'touched). In this momment (just before I would press touch sensor, voltage was 1.212v. Once I pressed touch sensor.....nothing happen. Voltage kept slowly dropping. I pressed it couple of times, but almost nothing happen. Except that in one point when the voltage was 1.195v, it jumped to 1.220v and again started dropping. I don't think these small voltage range differences are important, but I still described how everything went. I even recorded a 'small' clip with my phone, but its still too big to upload (> 40MB).

After this I pressed the On/OFf switch on extension cable to turn off the power board.

Then again, I was like 'lets check again' and I repeated the whole process again. Not much difference, but here it is:

1st step: zero voltage on POWER_EN (ofc, On/OFF swtich on extension cable was in OFF position).

2nd step: (extension cable On/Off switch in ON position). in next 7 sec, voltage reached its max of 1.202v and started dropping again.

3nd step: (extension cable On/Off switch in ON position, monitor turn ON touch sensor was 'touched). Sensor touched 17sec after I pressed exntion cable on/off switch in ON position). At the time voltage was 1.193. Then I touched the sensor, and...again nothing happen, except that voltage kept dropping slowly. At 34th second (from the moment when the extension cable on/off switch was turned ON), voltage dropped to 1.180v.



And, since everything was already connected, I took the time to measure a voltage on a BIG FAT cap (while main/logic board was still connected to a pwer board). Voltage on a BIG FAT cap was 384.5v

So, to sum things up:
==============
POWER_EN voltage (NOT connected to main wall socket): 0v
POWER_EN voltage (connected to main wall socket): 1.234v (and slowly dropping)
POWER_EN voltage (connected to main wall socket, and monitor turn ON touch sensor button touched): 1.212v (and still slowly dropping)

BIG FAT power board filter capacitor (while power board and main board were connected): 384.5v

I hope with this 2nd post, I provided the rest of the checkings you asked me to do. If there are more checks that needs to be done, please let me know (with ofcorse some instructions how to do it).

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

About 1-2 years ago... I had an Asus power adapter. I measured the voltage and it didn't gave the voltages that it should.... I knew that I should be careful of those electrolytic caps, so I wasn't touching that. But at one momment, somehow, I guess I touched contact that lead to those small caps, and that fcking sh1t feeling went through my whole body.

That's a familiar situation.

In my case, I was working on a TV board that had a short-circuit on one of its outputs. Because of that, the protection kicked in and PSU turned off. However, that PSU had no discharge resistor across its primary cap. So when I opened it and started touching / probing around, I got a nice sting across my fingers when I must have touched some parts across the primary side.

So if I had to guess anything about your power adapter, most likely the output power cord was shorted, making the adapter go into short-circuit protection and turning off its output completely... thus leaving the primary cap completely charged. Either that, or current sense resistor on main switching MOSFET on primary was blown, leaving no path for the big primary cap to discharge through.

So when you touched the small cap, it probably was in some way connected to the primary side and primary cap, and that's how you got the shock.

An offotopic question, if I may: (lets imagine) that I 'fix' this poor monitor (or in case some board is un-fixable, I boy a used one), and after putting back together all the parts, I'm about to turn on my monitor for the first time...

Is it possible (in case something is shorted), ...(or new 'used' spare board is shorted somewhere), to prevent further damage to other monitor components (boards), to use that 'light bulb' protection? I watched a YT clip where you put the socket with light bulb connected, and if something is shorted on the device that you are about to turn on, the light bulb will fully light up and you will know that something is shorted (and that way you would 'save' your device form further damage)?

Can you check this clips please:


^ it's explained for USA, but... I'm not sure if it is correct that 100W light bulb should be used in Europe, since we have here ~230v (and not 120v like in USA).


https://www.youtube.com/watch?v=wRFRwOnLsZI
https://www.youtube.com/watch?v=v_O0qoJn4xs

^ please check these clips. In the first clips, from what I can see...its an issue for european socket standard. Because you can connect cables to wall socket in both positions (if you rotate them for 180 degrees), so... I don't know if that could work, since the bulb should connect two ends of 'black' (main voltage line), but if you reverse the cable plug and put connect it to a wall socket, the bulb will connect two ends of white wire, and not black. Any idea about this? (sorry for the oftopic question)

Also I read among some YT comments that it can't work for any swithcing mode power supply because the bulb will start (and continue) to bling while device would try to start things up. So... I'm lost here...

[momaka]

Re: Samsung 2693HM - Doesn't turn on (no standby)

I guess I'll start backwards and answer your last reply first...

Is it possible (in case something is shorted), ...(or new 'used' spare board is shorted somewhere), to prevent further damage to other monitor components (boards), to use that 'light bulb' protection? I watched a YT clip where you put the socket with light bulb connected, and if something is shorted on the device that you are about to turn on, the light bulb will fully light up and you will know that something is shorted (and that way you would 'save' your device form further damage)?

I don't think I can give you a short answer on this, but I will try...

So the "dim bulb tester" (DBT) / series incandescent light bulb "trick" basically limits the amount of current (and also power) a device can pull. The main use for this device is typically when you're working on a *power supply* that has blown fuses or as the videos above show, for audio equipment (especially vintage stuff that hasn't been powered for very long time or amps that had blown output transistors.) There are a few other uses as well, but these two really are the main ones.

So for a short answer, unless your monitor's power supply had issues with blowing primary-side fuses, you probably won't have a use for this device. Even in a cases where you take boards from another monitor... anything that's not related to the power supply won't see any added protection from the DBT. Reason why is because modern-day switchmode power supplies (SMPS) have built-in short-circuit and other protections. If anything, you'll most likely run into an issue with trying to run your monitor on a DBT... and that has to do with the power-limiting nature of the DBT... but I will save that explanation for another time if you wish, since it can be a bit lengthy.

^ it's explained for USA, but... I'm not sure if it is correct that 100W light bulb should be used in Europe, since we have here ~230v (and not 120v like in USA).

The power of the bulb (i.e. rated Watts) is sized according to the test device - in particular to the load it is expected to pull from the wall and also depending on the design of the power supply in the device.

Again, there is a lot more on the above matter, but that's all I will put here to keep it brief.

https://www.youtube.com/watch?v=wRFRwOnLsZI
https://www.youtube.com/watch?v=v_O0qoJn4xs

^ please check these clips. In the first clips, from what I can see...its an issue for european socket standard. Because you can connect cables to wall socket in both positions (if you rotate them for 180 degrees), so... I don't know if that could work, since the bulb should connect two ends of 'black' (main voltage line), but if you reverse the cable plug and put connect it to a wall socket, the bulb will connect two ends of white wire, and not black. Any idea about this? (sorry for the oftopic question)

Yes, you guys have the Schuko plug in Europe, which in many places is reversible (i.e. Live and Neutral.... or Hot and Common as the video calls it... can be swapped if you flip the plug 180 degrees, like you said.)

But that doesn't matter, the DBT will still work the same. Only difference is that you won't know if the Live is going directly to the device or through the bulb... which depending on what you are working on may pose greater danger of shock hazard. But for SMPS and solid stated amplifiers testing, the phasing (i.e. which side is plugged into Live and which into Neutral) is pretty irrelevant.

Also I read among some YT comments that it can't work for any swithcing mode power supply because the bulb will start (and continue) to bling while device would try to start things up. So... I'm lost here...

It CAN work on an SMPS... but that's the tricky part.

In short: DBT will limit output power to your device to a MAXIMUM of 1/4 of the rated power of the bulb (so for a 100W bulb, you won't be able to pull more than 25 Watts with your device / power supply). And moreover, when that is true, the AC voltage across both the bulb and the test device will be 1/2 of the wall voltage. This is what makes it tricky for SMPS, because most are specified to work only within a certain range - typically 100-240V AC for "universal" devices (most monitors and small chargers, but always check label), 90-260V for most SMPS with APFC (which your monitor has), and 110-130V or 210-250V for most PC ATX PSUs with a voltage selector switch. So if the AC input voltage across your test device falls too low because of the DBT, it may not work correctly (for SMPS, you may indeed see the bulb flicker rapidly On and Off, as some of the YT comments noted.)

[momaka]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Voltages on the capacitors on the left side of the main (logic) board:
-----
C610 = 17.88v
C619 = 17.50v
C3045 = 1.073v
C621 = 1.587v


IC304:
-------
pin 1 = 5.225v
pin 2 = 0v
pin 3 = 5.223v

C3045.... that voltage looks weird. I haven't seen any ICs in a monitor application that need 1V (since 1.073V is pretty much close to either 1.0V or 1.1V... neither of which are standard.) Generally, standard voltages for most ICs and MCUs are 3.3V, 2.8V, 2.6V, 2.5V, 1.8V, 1.6V, 1.5V, 1.3V, 1.25V, and 1.2V. From these, 3.3V, 2.6/2.5, 1.8, and 1.3V are the most commonly seen ones. The voltage on C621 looks close enough to 1.6V (or 1.5V if meter is reading a bit high for whatever reason), so that one is probably OK.

Does the main IC or any IC on the logic/main board get really hot (as in, you can't hold your finger on it) after the monitor has been plugged in for a minute or so. You can touch the ICs on the main/logic board with your bare hand/finger to check temperatures, there aren't any dangerous voltage there. Just make sure your hand isn't wet or has metal filings, as you might short something out otherwise. (I know this is getting in "uncomfortable territory for you, asking you to touch stuff by bare hand, but it's actually pretty safe. You probably have 1000's of times greater chance of catching Coronavirus and getting complications from it than getting hurt from this, lol. ) Or if you still feel too uncomfortable to do that, then let the monitor sit powered for a minute or two, then disconnect from wall and check temperature on parts right away with your finger. This should tell you if anything had gotten hot.

C610 and C619 look like they are part of the same 18V rail, with C610 doing filter duty before L903 and C619 providing filtering after L903. I suppose it might be good to confirm that - just check resistance between the two (+) leads of caps C610 and C619 (with the monitor powered Off and disconnected from the wall, of course.)

And then there's IC304: looks like it's doing pass-through duty only, kind of like a MOSFET or BJT... but that doesn't make much sense, since its designator starts with IC and not Q. Can you tell me what part numbers you see written on IC304? I can't read it from any of the pictures (nothing wrong with them, btw, it's just IC304 is a small component.)

btw. after I pulled the plug that was connected to a power board, I checked the voltage of BIG FAT and it was already around 6v and dropping (I didn't checked instantly, but after a min or two). Then I checked the other caps on main (logic) board and out of 4 mentioned ^ above, only C619 had around 2.1v very slowly dropping. When I checked BIG FAT cap again, it had around 1.11v and dropping. Then I checked again C619 on main (logic) board and it had around 2.19v (and pretty stable, like it is in no rush to discharge). By now (3 hours later) I guess it discharged probably. Power board and main (logic) board were connected all the time, except that I pulled the plug that was attached to power board.

That's fine. We don't really care how fast or slow the voltage on the caps discharge after the monitor is unplugged from the wall. Only the big cap is important, and that's just for your personal safety reasons. When I work on monitors, I always check for voltage on the big cap before trying to remove the PSU from monitor. If less than 20-30V DC, I don't care. If over 50V, I take some caution. If over 100V, I discharge with 5K large resistor I have on my bench.

Also, I got a s*rvice manual for my monitor that I got from back in 2017 when I had issue with caps. So if you don't have it and want to check it out, let me know. I'll upload it. I wasn't sure if it's allowed to upload it, so I decided not to, for now.

Oh nice.
Yes, you're allowed to upload SMs here. Just make sure it's not too big (otherwise may not be able to attach it due to file size limits.)

Ok, I got it. Just one more question: Does that mean, that IF you ask me to measure a voltage of some other element on PRIMARY side, I would again touch negative leg of that BIG FAT cap and use my red (positive) probe to touch the positive leg of any other element that you ask me to measure its voltage? I'm asking if the black probe of my multimeter needs to be ALWAYS touching ONLY a negative leg of BIG FAT cap with black multimeter probe, while I would 'move' my red positive probe to a positive leg of any other elment inside PRIMARY area?

100% Correct.
And again, that's for the primary side only.
Your PSU appears to be working OK at least from the few measurements you showed, so most likely we won't have to do anything on the primary side.

Ok, but what about other boards connected to power board? Like main (logic) board? There are voltages which only comes from SECONDARY side of that transformer (located power board), so I would say that any element on main (logic) board can be measured by putting black multimeter probe to a screw rings hole? No danger there (for me or any element located on main-logic board). Correct?

Yes, 100% correct again.

Any voltage or signal that comes from the secondary side of the PSU is referenced to secondary ground (i.e. metal chassis or metal ring around PCB screw holes) and is pretty safe to touch (unless there are any voltages of 50V DC... which there are none on this monitor, except the CCFL inverter output where the CCFLs connect.)

What abotu T-CON board? If 3 boards (power-main-TCON) are connected together, I guess all voltages present on TCON board comming from SECONDARY tranformer side, so I can touch screw-hole ring with my negative probe? Right?

Yes.

And... what about inverter board? I has those small tranformers. And you said it has 700-1000v. That scares me so much. You said don't touch tranformers there. But...maybe I check voltages (for instance) on on capacitors (on inverter board) but touching screw-hole rings with negative probe, while using positive (red) probe to touch positive leg of a capacitor on inverter board)? Or I MUST touch negative capacitor leg directly with multimeter black probe? I'm asking because of those 700-1000v that you mantioned.

Inverter board ground is same as for other secondary side voltages, so same rule applies: use either metal chassis, metal ring around screw holes, or electrolytic cap negative lead (on the inverter board.)

Just avoid touching the transformers on the inverter board when it's powered, as that's when they may be outputting high voltage AC for the CCFLs. The good thing is that the moment you unplug the monitor, inverter CCFL voltages will are gone. There's no cap to hold the high voltages there, since it's all AC.

Thanks! I'm trying to be as fast as I can, while I'm doing my best to be as slow as I can. ...if this even make sense. In other words, I'll do it as fast as possible, but not before I understand everything I need, or what I think that I need to know). Sometimes, my mind is overwhelmed by the informations I receive.

Yeah, that's normal.
Honestly, whenever I do repairs that aren't time-sensitive, I always take my time as well, even if it's something pretty simple. Sometimes your mind figures things out "in the background" (can even be while you sleep or when you do something completely unrelated to electronics.) I've actually had a lot of A-ha moments about problems that I wasn't even thinking about at the time.

So if you need time, take it.

3 questions here:

1st:
I don't have aligator clips. Do I have to buy the one pair of multimeter cables that I can use instead of my regular probes?

You can, but you don't have to.

If it's more convenient (at least for now, since you don't do a whole lot of repairs), you can just use regular wire and twist it around your probes, then solder the other ends to whatever voltage points need measuring.

I used to do temporary things like that all the time in the beginning when I started repairing stuff and barely had any equipment other than a cheap multimeter and simple soldering iron. It's fine to do, but if you have to do it a lot, eventually it makes sense to get the right tools.

2nd:
Can I just buy (make) a wired cable that can have on both ends aligator clips, so one end will 'grab' the negative probe of my multimeter, and the other end will 'byte' the scew-hole ring?

Yes.

3rd:
since my monitor has that..'touch sensor' (or whats it called) and not regular button', if I manage somehow to pull out that small board which is used to power on my monitor when I touch the bottom-right corner on my monitor.... and when I have that small board 'out'....connected to a main (logic) board.... is there a chance I get shocked once I press the button (make short) so that I give a 'command' to a logic board to turn on the monitor? (I don't even know if that small board as a classic button, since its a touch sensor)

No, you won't get shock from that small board. It uses voltages from the main IC... so you're probably looking at 3.3V or less.

You likely won't find any buttons on it either. It reads what button was touched by detecting the capacity of your body when you place a finger near one of the sensors where a "button" is supposed to be. It's somewhat similar to smartphone touch screen.

[momaka]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Momaka, thank you for a detailed explanation! I think I (finally) understood your instructions and I finished checking voltages at POWER_EN pin (of main/logic board), that you asked me to measure.

Perfect! You did everything 100% correct.

So it looks like POWER_EN / PS_ON is stuck at 1.2V, or thereabouts. I think that means the main PS should be Off... However, the fact that you have 5.3V and 18V on the logic board and that the big cap also has 385V DC on it means the main PS is actually turned On.... which I find odd, as I expect APFC and main PS voltage to be present only when the monitor is turned On. When off, voltage on PS_ON should be different.

Because of this, could you do another measurement on PS_ON signal? This time, however, keep the logic/main board completely disconnected from power supply. Now, while checking voltage on pin PS_ON, plug in PSU to the wall and tell me what voltage you read. (And of course, since you don't have the logic board connected, you won't have the panel On/off touch board connected either, so that should make things simpler to measure.)

And, since everything was already connected, I took the time to measure a voltage on a BIG FAT cap (while main/logic board was still connected to a pwer board). Voltage on a BIG FAT cap was 384.5v

Yup, that's normal for when the APFC booster is working.
Without APFC, you're more likely to see 325-340V, depending on line voltage. (And for the voltage measurement at PS_ON with logic board disconnected, you'll likely see big cap voltage only at 325-340V, too.)

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Momaka, thanks again for your reply and for "dim bulb tester" (DMB) explanation.

Now, before I start another novel, I want to tell you that I (as you can see) uploaded some files. You'll find:

- Service Manual for Samsung 2693HM (split in 2 rar archives, because of its size)
- 2x 400% zoomed-in (most important) pages from service manual (pages 59 & 60) as jpeg images
- some datasheets of specific main(logic) board elements
- And also some images where I point to certain elements (or their service manual page location, so you don't have to waste time while trying to find them)

So... you can check them out if you want.

C3045.... that voltage looks weird. I haven't seen any ICs in a monitor application that need 1V (since 1.073V is pretty much close to either 1.0V or 1.1V... neither of which are standard.) Generally, standard voltages for most ICs and MCUs are 3.3V, 2.8V, 2.6V, 2.5V, 1.8V, 1.6V, 1.5V, 1.3V, 1.25V, and 1.2V. From these, 3.3V, 2.6/2.5, 1.8, and 1.3V are the most commonly seen ones. The voltage on C621 looks close enough to 1.6V (or 1.5V if meter is reading a bit high for whatever reason), so that one is probably OK.

I have checked Service Manual for this monitor (page 60), and I've found C3045 capacitor which 'revolves' around IC924. The schematics show that the 'output' voltage on that C3045 capacitor should be 1.8v (or 1.2v). I can't determ which voltage should be present (1.2v or 1.8v). I guess when the monitor is not powered it should have 1.2v, but when the monitor is powered it will go 'live' and have '+1.8v_LIVE' voltage? Correct?
Anyway, please check the service manual (page 60), or one of the images that I made by making a screenshot of that page from the manual. (I'll attach the image)

Also on the schematics, you can read near IC924 a marking 'MP1583DN'. I googled it, and it sais its: 'Monolithic Power Systems (MPS) MP1583DN-LF (3A, 23V, 385KHz) Step-Down Converter (regulator)'. I'll attach the datasheet for this one.

^ one extra question about this Step-Down converter (regulator): Since its datasheet sais it accept intput voltages from 4.75-23v, and oputputs 1.22v-21v, and since capacitor C3045 in Service Manual schematics show that it should have 1.8v (or 1.2v), that means, that the IC924 wont be hot. Because its input voltage is ~5v (which comes from 5V_MICOM connector pin), and his work wont be 'stressfull' to adjust voltage from 5v to 1.8v (or 1.2v), compared if it had to adjust input voltage of 23v to 1.8v (1.2v). Correct?

Does the main IC or any IC on the logic/main board get really hot (as in, you can't hold your finger on it) after the monitor has been plugged in for a minute or so. Or if you still feel too uncomfortable to do that, then let the monitor sit powered for a minute or two, then disconnect from wall and check temperature on parts right away with your finger. This should tell you if anything had gotten hot.

To answer on this question (and to check what you asked me about) you have to be more clear. My monitor is disassembled. So...when you say 'doe the..... after the MONITOR has been plugged for a minute or so' what do you mean by that?
Do I have to assemble the monitor again? (please don't say 'yes', I have issues to dissassemble it, because some parts wont come off easily and I already broke to plastic...'snaps' of back cover (good thing it has couple more so the cover will stay). I also had issue to remove that monitor frame because (again because of some plastic 'snaps') some decorative shiny plastic refused to come off for a long time.

So, do I have to connect again (only) power (PSU) board with main (logic) board, and with a monitor frame (which holds that touch sensor), and touch the sensor again, like I did when I was measuring POWER_EN pin voltage in my previous posts? Or...there is something else I have to do, before I can touch the main IC (or any other IC on the logic/main board), in order to let you know if they are hot or not? I know, you will say 'this guy, makes simple things complicated', but I'm not doing it on purpose, just want to have clear instruction of what is expected of me, while the things are measured (checked) in expected state.

You can touch the ICs on the main/logic board with your bare hand/finger to check temperatures, there aren't any dangerous voltage there. Just make sure your hand isn't wet or has metal filings, as you might short something out otherwise. (I know this is getting in "uncomfortable territory for you, asking you to touch stuff by bare hand, but it's actually pretty safe. You probably have 1000's of times greater chance of catching Coronavirus and getting complications from it than getting hurt from this, lol. )

^

I remember that I went to my neighbour and told him what I did and what happen. He started laughing, and said 'its nothing, it will pass, its good to get electrocuted from time to time'. After he said that last part, I was like '....of all the neighbours that I could talk about what happened, I just picked a joker'

And here you are now, talking to another joker (i.e. me.)
If I was there with your neighbor, I would probably have nodded in agreement when he said that.

haha, now I get it.

But, I always make sure that my fingers are not wet. Things is, they easily get sweat. Or shaking (like few days ago when I was checking the votages that I was requested to check).

C610 and C619 look like they are part of the same 18V rail, with C610 doing filter duty before L903 and C619 providing filtering after L903. I suppose it might be good to confirm that - just check resistance between the two (+) leads of caps C610 and C619 (with the monitor powered Off and disconnected from the wall, of course.)

I've attached the picture of the service manual caps location.
I mesured the resistance between 2 (+) leads (legs) of C610 and C619 caps, and...here is the strange thing:

When I put red probe to positive leg of C610 and black probe to positive leg of C619, resistance is 1.78 KOhm. BUT... when switch probes, so that black probe goes to positive leg of C610 and red probe to positive leg of C619 resistance is around 13-14MOhms, and dropping....dropping....dropping to 3MOhms (and keep dropping). I checked multiple times, just to be sure. (I attached the image as illustration)

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

And then there's IC304: looks like it's doing pass-through duty only, kind of like a MOSFET or BJT... but that doesn't make much sense, since its designator starts with IC and not Q. Can you tell me what part numbers you see written on IC304? I can't read it from any of the pictures (nothing wrong with them, btw, it's just IC304 is a small component.)

As for IC304 I made a small picture of the markings few posts back (you probabbly missed it). Its in post #25, (1st attached image). It sais: 6P 801

Here: https://www.badcaps.net/forum/attach...7&d=1604276645


Inside Service Manual of this monitor (page 59), you can see a schematics wtih IC304 included and there is a mark 'KIA7042AF-RTF' near it. I googled it and it is probably:

KEC Semicon KIA7042AF-RTF/P voltage detector (SOT-89 (SOT-89-3)).

From what I see on the schemantic it receive 5v voltage from +5V_MICOM pin of the main power board. So I would (as a newbie) conclude these voltages on IC304 are 'ok' since I measured 5.225v on pin 1 and 5.223v on pin 3 of the IC304. The only 'strange' thing which I don't understand is that inside PDF file for that IC304 KEC Semicon voltage detector, for 'my' KIA7042AF-RTF model, it sais that 'Detecting Voltage (Vs)' goes from 4.05-4.35 (but typical 4.2v). Maybe that means...'once' there are (at least) voltage of 4.05-4.35 on its pin 1, it'll do its 'thing' or... send the voltage to pin 3. Right? I'm a bit confused because voltages that I measued on both pin 1 and pin 2 are above 5v. Anyway, I will include PDF of that 'KEC Semicon KIA7042AF-RTF/P voltage detector' with this post.

When I work on monitors, I always check for voltage on the big cap before trying to remove the PSU from monitor. If less than 20-30V DC, I don't care. If over 50V, I take some caution. If over 100V, I discharge with 5K large resistor I have on my bench.

Can you link me a image of your resistor? Few years ago I bought one ceramic resistor (I think it was marked 10 Watts), but I can't find it. Now I look for it at local shop website, and I see there are resistors marked with high power (like 10w) but very low reistance. Or for low voltage. So, I'm guessing I should look for high power, hight resistance (5-10 KOhm) and high voltage, correct?

And... what about inverter board? I has those small tranformers. And you said it has 700-1000v. That scares me so much. You said don't touch tranformers there. But...maybe I check voltages (for instance) on on capacitors (on inverter board) but touching screw-hole rings with negative probe, while using positive (red) probe to touch positive leg of a capacitor on inverter board)? Or I MUST touch negative capacitor leg directly with multimeter black probe? I'm asking because of those 700-1000v that you mantioned.

Inverter board ground is same as for other secondary side voltages, so same rule applies: use either metal chassis, metal ring around screw holes, or electrolytic cap negative lead (on the inverter board.)

Just avoid touching the transformers on the inverter board when it's powered, as that's when they may be outputting high voltage AC for the CCFLs. The good thing is that the moment you unplug the monitor, inverter CCFL voltages will are gone. There's no cap to hold the high voltages there, since it's all AC.

You said AC two times, so I guess you didn't made a typo. Ok, here comes another of my many stupid questions: How can it be AC there on the inverter board, since its gets voltages from secondary tranformer side (located on Power PSU board)? I thought there are no AC voltages anywhere else except for the power board (transfomer primary area marked with white lines)

One extra (but) offtopic question: About 6-7 months ago, I disassembled one old 17" LG monitor. I wanted to see if there is maybe some cap leaked from preventing it to power up the monitor. And yes, I found the bulged cap. BUT, in the process of disassembling that monitor, I cut out one of the inverter connectors. There were 2 'holes' hard to access. From both holes there were 2x2 wires with 2 connectors. So it had 4 connectors total.
I don't want to bother you with this now, but can that connector be... 'patched' somehow, since wires are so small and can easily brake.

Another question is: so, no mattter what type of monitor with CCFL laps I try to power on, as soon as I pull the plug from the socket wall, there is no voltage charge left in CCFLs and I can touch them or their connectors, correct? I mean, they are not like capacitors that can hold charges after the device is turned off and cable pulled from the socket wall, right?

So it looks like POWER_EN / PS_ON is stuck at 1.2V, or thereabouts. I think that means the main PS should be Off... However, the fact that you have 5.3V and 18V on the logic board and that the big cap also has 385V DC on it means the main PS is actually turned On.... which I find odd, as I expect APFC and main PS voltage to be present only when the monitor is turned On. When off, voltage on PS_ON should be different.

Because of this, could you do another measurement on PS_ON signal? This time, however, keep the logic/main board completely disconnected from power supply. Now, while checking voltage on pin PS_ON, plug in PSU to the wall and tell me what voltage you read. (And of course, since you don't have the logic board connected, you won't have the panel On/off touch board connected either, so that should make things simpler to measure.)

OK, so I checked the voltage on PWR_ON/OF (PS_ON) pin on the power board.

Here is what I did:

I soldered a blue wire to GND pin of CNM803 connector (on power board). The other end of that blue wire I connected to black probe of my multimeter.
I soldered a red wire to PWR_ON/OFF (PS_ON) pin of CNM803 connector (on power board). The other end of that red wire I connected to red probe of my multimeter.
Then I connected power board with its power cable to an extension cable (with a ON/OFF switch on it). Then that extension cable attached to a wall socket.

In that moment multimeter was showing 0v (ofc, since exnesion cable ON/OFF switch was in 'off' position).
Then I pressed the extension cable switch to ON position and....nothing happen. 0v (zero volts). As it should be, right?

Since I could, I took time to measure a stendby voltage on that CNM803 connector. It was 5.24v. Again, good, I think.

So to sum things up:

PWR_ON/OFF voltage on power board CNM803 connector: 0v (zero volts)
ST_BY (standby) voltage on power board CNM803 connector: 5.24v




Ok, I guess thats all for now. I only didn't answer your question about how much (IF any of) ICs getting hot. Will try to answer that question after (IF) you decide to answer on this new chain of posts I just made. Sorry about that.

I'm doing it this (long) way so maybe one day, if I decide to check something I can re-read what was done, and/or if one day some poor soul with the same issue and the same monitor decide to visit this topic so he can read and maybe get the answers that bothers him, like they bother me right now.

Thanks again, and sorry for a fact that I keep making new questions.

[twist3r]

Re: Samsung 2693HM - Doesn't turn on (no standby)

Hmm. It took me some time to make those JPG images of pages 59 and 60 of the service manual with 400% zoomed-in clarity in photoshop. But now when I uploaded them, I see that they are not as clear as they were on my hard drive. I guess there was some 'compression thing' going on while the vBulletin forum software attached them. So I'll upload these 2 Hi-Res pages in a rar archive, so you can use them (if you don't like reading PDF service manual).

Reason for making these 2 pages (59 & 60) in Hi-Res is: You can't search for some elements on the schematics inside service manual. For instance I coudn't use a seach option to find C610 or C619 (or C3045) capacitors. It only finds some of them in the list section. So since the search function in Acrobat Reader is useless for this Service manual (even if the schematic is 'vectored' and pages are not made out of bare scanned photos), I was thinking maybe you would like more to watch at the Hi-Res image instead of page in service manual.

[momaka]

Re: Samsung 2693HM - Doesn't turn on (no standby)

I have checked Service Manual for this monitor (page 60), and I've found C3045 capacitor which 'revolves' around IC924. The schematics show that the 'output' voltage on that C3045 capacitor should be 1.8v (or 1.2v). I can't determ which voltage should be present (1.2v or 1.8v). I guess when the monitor is not powered it should have 1.2v, but when the monitor is powered it will go 'live' and have '+1.8v_LIVE' voltage? Correct?

Well, good thing you provided the SM (service manual) and IC924 datasheet.
From the MPS MP1583DN (IC924) datasheet, the reference/feedback voltage V_FB of the IC is typically 1.222V (see page 3, parameter "V_FB"). Resistors R1 and R2 in the app note in the datasheet set the output voltage. In the SM of the monitor, we can see these resistors correspond to R3027 and R3050. From the picture of the mainboard you provided, we can see that R3027 has a big zero (0) written on it, so it's a zero Ohm resistor (i.e. a jumper)... which means the output of IC924 should equal to the reference voltage, V_FB... so that means 1.2V is the correct voltage output and 1.8V is not. I think also any bold text in the SM is basically to indicate a correction or later revision. (And for example, you can see that for the 2493HM model of the monitor, there are certain parts that say "DELETE", which probably means those parts of the circuit are not installed. So in other words, the bold text supersedes anything else written on the schematic.)

With that said, that 1.2V rail is still a bit too low. According to MP1583DN datasheet, V_FB can be as low as 1.194V and as high as 1.25V... so even if your multimeter is slightly off, it should still measure close to those values if IC924 is working correctly. And on that note, I think IC924 IS working fine. However, the monitor SM says that IC924 gets its enable signal from the output of 3.3V_LIVE (i.e. the voltage generated by IC602.)

Now, in my last post, I mistakenly assumed that since the voltage on C621 is close to 1.6V, then that must be what the IC is supposed to output. However, that is INCORRECT. The fact that you are getting only about 1.6V on the output of the 3.3V rail when both 5V_MICOM / ST_5.2V and +18V_IN are more or less normal, then that means there is something wrong with the 3.3V rail and this is where we should start digging deeper.

With the power turned OFF and logic/mainboard (sorry if I keep alternating between calling it logic board or mainboard... it's the same thing here) disconnected from PSU board and all other boards, measure the RESISTANCE between a ground (screw hole metal ring or C621 negative '-' terminal, whichever you prefer) and positive (+) terminal of C621. Keep the multimeter connected for 2-4 seconds and tell me what you see. Stable resistance? Or resistance climbing? (And approximate #'s, if value is climbing - this doesn't need to be exact.) Post back what results you get here.

On that note, you said your monitor died when cable co. came in and installed new tuner box and had said box connected to monitor. If that really was the case and not a coincidence (after all, it could be, despite the guy saying this happens all the time - we still don't know the problem, so we have to keep open mind about any possible scenario), then I suspect there may also be shorted protection diode(s) on the HDMI or DVI-I (or whichever input you used) that's pulling the 3.3V rail down. In particular, I was looking at the monitor SM and on page 79, look at the schematic of the HDMI and DVI_I inputs. For the HDMI connector, diodes D105 through D112 provide anti-static / surge protection on the signal lines by clamping high voltages to the 3.3V rail and negative voltages to ground. Likewise, diodes D129 and D130 provide clamping to 5V_DDC and 5V_DDCH rails. On the DVI_I connector, it's the same scheme with the surge protection - you have diodes D121 through D128 for clamping signal lines to 3.3V or ground and diode D133 providing protection on SCL and SDA lines.

Thus, since the 3.3V line is low, it is possible that one of these diodes (in particular diodes D105-D112 and D121-D128) to be shorted. Again, with the power OFF and mainboard disconnected from all other boards, you can check these diodes either on RESISTANCE setting or in DIODE MODE. Just for consistency, let's use RESISTANCE mode. These are the tests to carry out:

1) Place red MM probe on pin #1 of diode (see page 79 of SM - it shows pin numbers for these diodes and how they are wired) and black MM probe on pin #3. You may or may not see a reading on your multimeter, but if you do, it should NOT be lower than probably 200-400 Ohms (if it is, report what you measured.) Now reverse the positions of the red and black MM probes on pins #1 and 3. Your MM should show very high resistance or OL. If not, report what you get.

2) Place red MM probe on pin #3 of diode and black MM probe on pin #2. You may or may not see a reading on your multimeter, but if you do, it should NOT be lower than probably 200-400 Ohms (if it is, report what you measured.) Now reverse the positions of the red and black MM probes on pins #3 and 2. Your MM should show very high resistance or OL. If not, report what you get.

Repeat the above tests for all protection diodes (D105-D112 and D121-D128).
You don't need to report all resistances back here. But if you do, perhaps do it in this format so it's easier to read.
Dxxx
Test 1: resistance A, resistance B (reversed probes)
Test 2: resistance A, resistance B (reversed probes)
.
.
and etc.

^ one extra question about this Step-Down converter (regulator): Since its datasheet sais it accept intput voltages from 4.75-23v, and oputputs 1.22v-21v, and since capacitor C3045 in Service Manual schematics show that it should have 1.8v (or 1.2v), that means, that the IC924 wont be hot. Because its input voltage is ~5v (which comes from 5V_MICOM connector pin), and his work wont be 'stressfull' to adjust voltage from 5v to 1.8v (or 1.2v), compared if it had to adjust input voltage of 23v to 1.8v (1.2v). Correct?

So not quite.
Because MP1583DN is a switching-type (often called buck) converter/regulator, its efficiency is not necessarily lower at lower voltages. That would be the case with linear regulators, which basically act like variable resistances in order to drop a higher voltage to a lower one. Linear regulators are not very efficient, and indeed the higher the input voltage, the more inefficient and and more heat they produce. Conversely, buck regulators use an inductor and output capacitors to do the voltage conversion, so they are much more efficient. If you've worked on or observed PC desktop motherboards in more detail, you've probably noted that they always have inductors and capacitors around the CPU area. All of those are buck regulators that generate the low voltage, high current needed by the CPU to operate. The reason they are used and not linear regulators is because this would be a very challenging task with linear regulators because of all of the heat they would generate.

But to answer your above question shortly: No, usually switching / buck regulators actually have higher efficiency at higher voltages... to an extent, of course.

To answer on this question (and to check what you asked me about) you have to be more clear. My monitor is disassembled. So...when you say 'doe the..... after the MONITOR has been plugged for a minute or so' what do you mean by that?
Do I have to assemble the monitor again?

Oh, sorry about that.
By MONITOR, I meant just PSU board, logic board, and ON/OFF button board... as that's all we really need at this point in troubleshooting. T-con and inverter board are not needed.

So NO, you do NOT need to assemble the monitor.
(It would be terrible if you had to. I remember servicing PS3 consoles back in the day - those you had to assemble at least partially to test, unlike the Xbox 360's. As such, I really hated servicing the PS3's.)

So, do I have to connect again (only) power (PSU) board with main (logic) board, and with a monitor frame (which holds that touch sensor), and touch the sensor again, like I did when I was measuring POWER_EN pin voltage in my previous posts?

Yup, that's it.

I've attached the picture of the service manual caps location.
I mesured the resistance between 2 (+) leads (legs) of C610 and C619 caps, and...here is the strange thing:

When I put red probe to positive leg of C610 and black probe to positive leg of C619, resistance is 1.78 KOhm. BUT... when switch probes, so that black probe goes to positive leg of C610 and red probe to positive leg of C619 resistance is around 13-14MOhms, and dropping....dropping....dropping to 3MOhms (and keep dropping). I checked multiple times, just to be sure. (I attached the image as illustration)

OK, no worries about that one then.

From the monitor SM on page 81, we can see that C610 is connected to the "raw" 18V input from connector CN600, whereas C619 is connected after it through Schottky diode D602 and inductor L903. This explains why the voltage you measured on C610 was slightly higher than at C619 (i.e. the slight voltage drop from D602.) In the absence of the 18V rail (i.e. when the monitor is in standby or soft off mode), the ST_5V / +5V_MICOM rail will be feeding into C619 through Schottky diode D601, so then C619 will only have ~5V.

So yeah... we're good with that step here and nothing further to check on it.

More text coming your way to answer the other questions...