Samsung monitor won't turn on. (Syncmaster 941BW)

[momaka]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Do you plan on doing lots of repairs in the future? If not, just grab a cheap iron and solder and that's it.

Here's a complete set of everything:
http://www.ebay.com/itm/New-14in1-60...item58bdcdaaa2
^ I don't know how good the soldering iron is in that kit. Going by the feedback, it seems like a very very cheap iron. But it might just do for the repair you want to use it for.
Also don't leave it unattended, since it more than likely lacks UL testing certifications.

Home Depot budget choices (going by price from L to H):
http://www.homedepot.com/p/Aven-40-W...7521/206311976
http://www.homedepot.com/p/Hakko-60-...ED-P/204215957
http://www.homedepot.com/p/Hakko-40-...-1-P/204215977

And while there, grab some solder too:
http://www.homedepot.com/p/Aven-20g-...7551/206320645

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Okay OMFG... this has now officially turned into a pure nightmare for me Lol..

I'm trying to pick out the best deal (and quality, at the same time) soldering iron and associated supplies.. and tried checking 3 different places, Home Depot, Ebay, and Newegg.com.

And there's just TOO many choices lmao! I've been stuck in a constant OCD loop for around 3-4 hours now.. where I just.. can't decide.. *screams out loud*



WhatToDo...

[momaka]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

^ The big black thingy with the text "TMS92515CT" (I supposed that is the part number of the transformer too, if you are looking for replacements... but first, try the caps, then we will see).

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Had a couple of these monitors in the past and it was the inverter transformer had a job getting them and not sure if still available

Hmm, is that one of the components on the power board itself? And if so, do you think you could point it out to me, via one of the pics I've uploaded?

Thank you for the info though either way!

[visionman]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Had a couple of these monitors in the past and it was the inverter transformer had a job getting them and not sure if still available

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

I just wanted to say thank you to anyone/everyone that helped me out in this post. I'm the type of person, that I'll go to just about ANY possible length to help out someone else, whenever I'm able to. And also the type that usually doesn't go and ask for help most of the time, unless I REALLY need it badly. Out of the few times I have actually went and posted on a forum somewhere though, asking for help, most of the time I've not been able to get it. And perhaps, I just wasn't posting in the right place to begin with all those times, but that's really beside the point I guess. So yes, thank you all very much, your help has meant quite a bit more to me then I could ever express in words.

But now a little update, I suppose:

As it is now, my boss still hasn't paid my invoice, so I can't really order the equipment I need to repair the board yet. Due to how important having all 3 of my monitors is for work. I was just going to order another board, and then do the repairs on my own once I got the proper supplies and had the time to practice a bit. But since I couldn't find any boards in the U.S. (aka, would have taken WAY too long to get one), I just ordered a new monitor for now. Although, if anyone knows a place in the U.S where I can get a Samsung 940NW 930BA LCD Power Board PWI1904SJ(A) LEVEL3 LR76377, please do let me know haha!

So once I finally get paid, and am able to get the proper supplies, then I'll proceed to try and fix my board then. I'll update this post again once I get to this point, although not sure how soon that will be.

So thank you all again, and hope to see you again sometime soon!

[momaka]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Here's a list of the info I could find on my caps:

3x Samwha WB | 25v, 47OuF, 105c(M), X9A Pet
1x Samwha WB | 16v, 1000uF, 105c(M), X9A Pet
2x Samwha WB | 25v, 330uF, 105c(M), X9A Pet
1x Samwha WB | 50v, 1uF, 105c(M), X9A Pet
1x Samwha WB | 35v, 47uF, 105c(M), X9A Pet

Looks like those Samwha WB caps are equivalent to Chemicon KZE, Rubycon ZL, and Nichicon HD. Other compatible series would be Panasonic FM. You could also use Nichicon HW and Panasonic FR, but you will have to use 680 uF instead 470 uF for the 25V caps (which shouldn't be a problem). And if you can't find those series, then go for something on the previous list I made.

Although.. I'm not a very good solderer. But I think it's partly just from lack of real practice, and also from lack of not knowing how to properly do it and/or just not having all the right tools.

Yeah, soldering is not that hard at all, especially if you have decent tools.

Can you suggest a good guide, and maybe even also what all I'd need material-wise to do it properly?

Tools:
* 40-60 Watt soldering iron. 30-35 Watt iron will work too, but you might struggle a little bit.
* rosin core solder... preferably 60/40 or 63/37 Lead/Tin. If you haven't soldered before, avoid lead-free for now (it takes a bit higher temperature to melt).
* stainless steel needle or cork board tack (used for clearing holes filled with solder on the board once the parts are removed)
* wet sponge or damp paper towel or brass shavings (for cleaning the iron's tip)
* (optional) * flux pen or liquid or gel flux. Do NOT use plumber's flux though, as most of it is highly active and can damage the traces on your board.

How to remove caps:
1. Plug in the iron and let it heat up for at least a few minutes. It should get hot enough that when you apply some solder to its tip, the solder will melt instantly.
2. Clean the iron tip from excess solder.
3. Pick a capacitor you want to remove. On solder-side of the board, put the iron on each capacitor leg and apply some fresh solder, making sure that the solder melts well on the joint. This could take 1 to 2 seconds (but don't worry about leaving on the iron for a bit longer if needed too. Up to 10 seconds should be plenty to melt the solder and not damage anything. If the solder doesn't melt in that time, either your iron tip is not hot enough yet, or you are holding the iron at an angle that is too perpendicular relative to the board.)
4. Once you do step 3 above, use only the soldering iron and the method below to "walk" out each capacitor:
method: https://www.badcaps.net/forum/showpo...7&postcount=23
5. With the capacitor removed, now you need to clear the holes one the board where the capacitor was. Heat the solder joints where the capacitor was and use the stainless steel needle or cork board tack to push out the solder from the hole.
6. Once you clear the holes, all that's left to do is put the new capacitor in, cut its leads, and solder it on the board with fresh solder again.
7. If you couldn't clear the holes in step 5, you could instead trim the leads of the new capacitor and "walk" it in the same way you took the old capacitor out.

Useful tip #1: if for some reason you have applied too much solder on a joint and it looks way too blobby, this is where the optional flux pen will come in handy. Apply some flux to the blobby joint, then hold the board vertically with one hand and scoop the solder with the hot iron in your other hand.

I have a TON of old mobo's, that I've saved just for such an occasion, actually.. So I have something to "practice" on first, once I have everything I need.

That's very good. Yes, definitely practice on those boards. Just make sure to avoid trying the caps around the CPU first, as those are probably the hardest to remove. In fact, just about any cap on a motherboard is much harder to remove than it is in a monitor power supply. So if you can successfully remove caps on a motherboard, the power supply will be a breeze.

Lol, I'm ALWAYS feeling a bit adventurous, I found my way here, didn't I?
But only 2..? Would it matter where they were on the board then, like one in each of the current 2 groups of two?

Well, from what I can tell from the first picture you posted of the underside (since it is not very clear), those 4 diodes are grouped in pairs. Each pair is in parallel. The new rectifiers I mentioned in my previous post have much superior specs, so one of them can easily replace two diodes.

Yup, it was showing at like.. 14.02, assuming that's close enough, but you would know better probably.

Good enough indeed. The "15 V" suppy is used mostly by the inverter, and most inverters will work with anything down to 12V or sometimes even less.

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

I can't think of anything to check. Perhaps look at the joints on the white power connector first (the one that is used to give power to the logic/video board). If it looks good, then I guess it is time for a recap.

Sometimes, the voltages may appear correct, but the caps could still be bad and letting excessive ripple through. I had a Gateway monitor behave in a very strange manner, even though all voltages from its power supply appeared normal. After doing a recap, all problems went away suddenly.

Just because the caps aren't bulged doesn't mean they aren't bad or starting to go bad . So next stop for you will be Digikey, Mouser, or some other place to get reputable caps (avoid eBay for now - too many counterfeit caps to sort through. If you don't have the eyes for it, you will likely get burned there.) You don't need to replace the big, high voltage cap on the board, but the other electrolytic caps need to go.

If you need help picking the right replacements, please provide some info on the existing caps, such as:
brand, series (usually or or three letters), voltage rating, capacitance rating, diameter (in mm), and height (also in mm).

In general these caps brands and series will work in most monitors:
Panasonic FC, FR, FM
Nichicon PW, PS, PM, PJ, HE, HW
Chemicon LXZ, LXV, LXY, KY, KZE, KMY
Rubycon ZL, and possibly ZLJ

Here's a list of the info I could find on my caps:

3x Samwha WB | 25v, 47OuF, 105c(M), X9A Pet
1x Samwha WB | 16v, 1000uF, 105c(M), X9A Pet
2x Samwha WB | 25v, 330uF, 105c(M), X9A Pet
1x Samwha WB | 50v, 1uF, 105c(M), X9A Pet
1x Samwha WB | 35v, 47uF, 105c(M), X9A Pet

Although.. I'm not a very good solderer. But I think it's partly just from lack of real practice, and also from lack of not knowing how to properly do it and/or just not having all the right tools. Can you suggest a good guide, and maybe even also what all I'd need material-wise to do it properly? I have a TON of old mobo's, that I've saved just for such an occasion, actually.. So I have something to "practice" on first, once I have everything I need.

Also forgot to mention...
the heat from those hot diodes (where the PCB is darkened) has probably shrotened the lives of the caps quite a bit (even if they are still in spec). So it is a good idea to change the caps anyways.

Now if you are feeling a bit adventurous, you should also replace those hot diodes with something better, like STPS1545D or MBR1060G. You will only need two.

Lol, I'm ALWAYS feeling a bit adventurous, I found my way here, didn't I?
But only 2..? Would it matter where they were on the board then, like one in each of the current 2 groups of two?

BTW, the 15VDC is also present at the pins, right.

Yup, it was showing at like.. 14.02, assuming that's close enough, but you would know better probably.

[budm]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

BTW, the 15VDC is also present at the pins, right.

[momaka]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Also forgot to mention...
the heat from those hot diodes (where the PCB is darkened) has probably shrotened the lives of the caps quite a bit (even if they are still in spec). So it is a good idea to change the caps anyways.

Now if you are feeling a bit adventurous, you should also replace those hot diodes with something better, like STPS1545D or MBR1060G. You will only need two.

[momaka]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Ok so.. I took out the power supply from the other monitor, and put it in the "bad" one. It came right on, and I'm using it as we speak. So, that means apparently the other power supply WAS bad, then..?

But according to the tests, it seemed to be good, right? Is there anything else in particular on it, that I can check, to see if I can find out where the problem is coming from?

I can't think of anything to check. Perhaps look at the joints on the white power connector first (the one that is used to give power to the logic/video board). If it looks good, then I guess it is time for a recap.

Sometimes, the voltages may appear correct, but the caps could still be bad and letting excessive ripple through. I had a Gateway monitor behave in a very strange manner, even though all voltages from its power supply appeared normal. After doing a recap, all problems went away suddenly.

Just because the caps aren't bulged doesn't mean they aren't bad or starting to go bad . So next stop for you will be Digikey, Mouser, or some other place to get reputable caps (avoid eBay for now - too many counterfeit caps to sort through. If you don't have the eyes for it, you will likely get burned there.) You don't need to replace the big, high voltage cap on the board, but the other electrolytic caps need to go.

If you need help picking the right replacements, please provide some info on the existing caps, such as:
brand, series (usually or or three letters), voltage rating, capacitance rating, diameter (in mm), and height (also in mm).

In general these caps brands and series will work in most monitors:
Panasonic FC, FR, FM
Nichicon PW, PS, PM, PJ, HE, HW
Chemicon LXZ, LXV, LXY, KY, KZE, KMY
Rubycon ZL, and possibly ZLJ

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Ok so.. I took out the power supply from the other monitor, and put it in the "bad" one. It came right on, and I'm using it as we speak. So, that means apparently the other power supply WAS bad, then..?

But according to the tests, it seemed to be good, right? Is there anything else in particular on it, that I can check, to see if I can find out where the problem is coming from?

Yep, the power supply section is working.
So for sure you do not see any indicator lights on the front bezel of the monitor at all?

And nope, I didn't before.




This is kind of the story of my life, though... Weird ass shit like this happening Lol.. If you ONLY knew..

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Those readings mean both the fuse and the thermistor are good.

Since you also checked the voltage on the white connector and you found that there is about 5V, then that means the power supply IS likely working okay.

Question:
Did you try swapping the power supplies from your working and non-working monitors? This will help determine if it is the power supply. The fact that you got about 5V from the (supposedly) bad power supply means that it actually might not be bad as it was initially assumed.

Nope, I haven't yet, but I guess that's the next step then. Most people would have tried that first, I guess. But I didn't for one sole reason.

Which is, with my luck, something would end up it up if I had tried that first haha.. Let's just say, my luck is so bad, that there's a better chance that I could've touched the connectors of that 450VDC Cap with a big metal object (while it was plugged in..) and only gotten a little static shock, then that my spare monitor would've still worked afterwards.

Luckily, I should be ok now, since I didn't try that first haha..

[budm]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Yep, the power supply section is working.
So for sure you do not see any indicator lights on the front bezel of the monitor at all?

[momaka]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

Ok so, I just now finished checking them. The fuse was showing up at 1.0 Ohm, and the thermistor way up at 7.5 Ohms.

Those readings mean both the fuse and the thermistor are good.

Since you also checked the voltage on the white connector and you found that there is about 5V, then that means the power supply IS likely working okay.

Question:
Did you try swapping the power supplies from your working and non-working monitors? This will help determine if it is the power supply. The fact that you got about 5V from the (supposedly) bad power supply means that it actually might not be bad as it was initially assumed.

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

OK, let test the DCV on that white connector of the power supply board that goes to the main board, you can test the power supply board by itself without having other board or the lamps connected, just the power cord.
There are the GND pins (3) that the black probe of the meter will be connected to (any one of the 3 pins), then the red probe will be connected to the +5V pin. Meter set to DCV 20 will be fine.

Yup, it's showing around 5.13V.

[budm]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

OK, let test the DCV on that white connector of the power supply board that goes to the main board, you can test the power supply board by itself without having other board or the lamps connected, just the power cord.
There are the GND pins (3) that the black probe of the meter will be connected to (any one of the 3 pins), then the red probe will be connected to the +5V pin. Meter set to DCV 20 will be fine.

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

The next thing you need to do is to find out if you do have 160~170VDC reading between the two legs of the main filter cap (the big 450VDC Cap laying on its side), this is where you MUST be real careful since you will be making the measurement in the PRIMARY DEADLY SIDE of the circuit, you need to have at least the Voltage on the cap before going further.

Should I assume that the best way to do that, is to lay the board back into it's "slot" in the case, and then test it by placing the leads onto the associated pins on the bottom side of the board? And if so, what should I set my multimeter at, DCV (20)? And last, but not least, I'm assuming that in this case, it doesn't matter which lead is on which pin, right?

BTW, the small white connector of the power supply/inverter board that goes to the main board has pin names and numbers to tell you what they are, did you verify that none of the pins have Voltages?

If you mean, the small white connector that goes from the power supply board, to the other board, then yes. Assuming that's the one you mean though, since the other 2 white connectors appear to go to the monitor. I set my multimeter to DCV (20) and placed the COM lead onto one of the NEG pins, and then tested each of the other pins. If I didn't test the correct one, OR if I did it incorrectly, please do let me know though.

[budm]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

The nect thing you need to do is to find out if you do have 160~170VDC reading between the two legs of the main filter cap (the big 450VDC Cap laying on its side), this is where you MUST be real careful since you will be making the measurement in the PRIMAY DEADLY SIDE of the circuit, you need to have at least the Voltage on the cap before going further.
BTW, the small white connector of the power supply/inverter board that goes to the main board has pin names and numbers to tell you what they are, did you verify that none of the pins have Voltages?

[TheCockroach]

Re: Samsung monitor won't turn on. (Syncmaster 941BW)

The next thing you will want to do is check the HOT side fuse and thermistor, as Joe Black suggested. No need to test the bridge rectifier yet (if it is blown, this will almost always cause the fuse to blow as well... so unless the fuse is blown, don't bother checking it). You can check these components while they are on the board (i.e. you don't have to remove them). The fuse is that round red cylinder, right behind where the power cable jack is. The thermistor is to the left of that (using your second attached picture as a reference) - it is green in color, and sits right next to that white-box capacitors (an X safety cap, to be exact). The thermistor is marked on the board as "TH01".

What you have to do to measure the fuse and the thermistor is set your multimeter to continuity (beep) mode and make sure that you get a audible beeping sound when you put the multimeter probes on the metal leads of those components (first check the fuse, then the thermistor). Alternatively, instead of using the continuity mode, you could also use the lowest resistance scale on your multimeter (usually 200 Ohms on manual-range meters) and see that both the fuse and the thermistor read less than 5 Ohms. Regardless of which way you do this, make sure the monitor is unplugged! The only time you will ever need the monitor plugged in while troubleshooting is if we ask you to measure DC voltages. For everything else, keep it unplugged.

Once you get these troubleshooting steps done, we will continue from there.

Ok so, I just now finished checking them. The fuse was showing up at 1.0 Ohm, and the thermistor way up at 7.5 Ohms.

I'll assume that that means it's definitely the power supply, so I guess now it's just up to what to do about it, and if it's something I can fix myself or not. We'll see though, I guess!