Getting started with troubleshooting [Samsung 245BW]

[nerdbot]

Re: Getting started with troubleshooting

Another update:

I did a lot more reading on here, mainly the threads about no power at all. First thing I did was check my fuses on my power board for continuity. I don't quite know what that means, and I'm not sure that I did it right, but here's what I did:

1. Left the fuses on the power board
2. Set my DMM to my 200 ohms
3. Touched one lead to the metal end on one side fuse, and the other lead to the other metal end on the other side of the fuse

Both fuses measured between 0.2-0.5 ohms. From the other threads I read, I heard the two possible options were either 0 ohms or infinite. Is 0.2-0.5 ohms "close enough" to 0? Or does this indicate the fuses are bad?

I also found this post from PlainBill:

https://www.badcaps.net/forum/showpo...5&postcount=15

Not quite correct.
U7 is the reset controller for the processor on the signal card. If it is bad the processor will not start, and the power LED will not come on. You WILL still have the normal voltages out of the power supply.
PlainBill

Correct me if I'm wrong, but this seems to be the scenario I'm experiencing? When it's just the power board by itself with power, the S_B pin shows 5.3V. When I connect the logic board (where I assume the reset controller is located), the S_B pin voltage drops to 3V-4.3V. Does this indicate a bad reset controller?

If so, I'm not sure how to identify which chip is the reset controller. Based off the pictures I've seen in the other threads, I see a lot of 3 pin chips (1 on one side, 2 on the other) on my logic board. Once I know where the reset controller is, I'll certainly try either removing it or the shorting out trick you guys have previously mentioned to other users here.

Finally, I was also able to locate the service manual for the 245BW and I attached a screenshot of the "No power" troubleshooting section. At step 1, I did not get 5V at pins 3, 4, or 5 of IC705.

The IC705 chip is an AnaChip AP1501 "150Khz, 3A PWM Buck DC/DC Converter", and I downloaded the datasheet:
http://www.alldatasheet.com/datashee...IP/AP1501.html

I'm at work right now, and didn't write down the exact voltage measurements of this chip from last night, but I do know it was somewhere between 2V-3.5V for pins 4 and pin 5. To measure the voltage on pins 4 and 5, I put the black lead on pin 3 (ground) and then the red lead on pins 4 and 5. Was that correct?

The flowchart was informative, but it would be nice to know what IC705, IC703, and IC310 do. I was able to locate IC705 (and find it's general description) and IC703 (not sure what it does though) on the logic board, and neither of those look like a reset controller. When I get home, I'll try to locate IC310. Is it possible that IC310 is the reset controller?

According to the troubleshooting flowchart, the lack of 5V on pins 4 and 5, I should check the SMPS, like PlainBill suggested. Since I've replaced all the caps on power board, and it seems to be functioning when it's the only thing connected, that's what lead me down the reset controller path. Was this a reasonable deduction? Or is it an open resistor on the power board? I posted some of the Ohm measurements of the resistors in the area of the SMPS controller in my previous post, but I don't know if these values are "normal" or bad. I've been trying to understand the STR-A159 datasheet to try and figure out which resistors in the diagram match with the actual resistors on the power board, but I've only been able to guess at a couple.

I feel like I'm starting to get all the various puzzle pieces to understand the problem, but not quite enough knowledge to actually complete the puzzle. Any suggestions or assistance would be greatly appreciated!

[nerdbot]

Re: Getting started with troubleshooting

Hi Retiredcaps,

Sorry for the slow reply, I was reading the megathread a few times and also looking for pictures referencing RB805.

Unfortunately, my power board is different than the one most people have in the 245BW megathread. Mine is a BN44-00195A, whereas it seems most people are referring to the BN44-00173A board in the megathread.

I looked at the picture in this post to get an idea of the general area to look in:
https://www.badcaps.net/forum/showpo...4&postcount=37

That general area on my board seems to be where PlainBill and newbie1 identified the SMPS chip, and PlainBill suggested I replace those 3 capacitors. In that area on my board, I was able to identify the following resistors:

(Identified from the top of the board)
RB801
RB802
RB803
RB808

(Identified from the underside of the board)
RB804
RB813

I've attached a closeup of the underside of the board beneath the SMPS chip (STR-A6159). Then, using the link from Newbie1 as a starting point, I found the datasheet for the STR-A6159:

http://pdf1.alldatasheet.com/datashe...STR-A6159.html

I did my best to understand the datasheet, and I measured the resistance of the above mentioned resistors:



RB801 (R91 from the datasheet?) - 89k ohms
RB802 - 98k ohms
RB803 - 47 ohms
RB808 (R3 from the datasheet?) - 2.2 ohms

RB804 - 1.3 ohms
RB813 - 3.24k ohms

I'm actually not sure about RB813. When I measure it on the "20K ohms" setting, I get "3.24". But if I switch it to "200K ohms" setting, I measure "18.8"

Also, unrelated to resistance measurements, a few more observations I've made:

- As mentioned before, with no logic board attached, the S_B pin measures 5.3V

- With the logic board attached, the S_B pin almost always measures around 3.5-4.3V

- I say "almost" because if I leave the boards unpowered for a "long" time (where by unscientific measurement, "long" = overnight), and plug everything (logic board, power board, and front bezel connector) back in, I can get the standby light on the bezel to come on (solid, not blinking) and the S_B pin reads 5.3V and the 5.2V_ST pin on the logic board also registers 5.2V-5.3V. However, this only lasts for a few seconds, and the standby light goes off and the voltage on the S_B and 5.2V_ST pins go back to 3.5-4.3V. I also noticed when supplying power after leaving it off overnight, that the power button pulsates and slowly gets brighter until it turns solid - different than the normal blinking when the monitor is in "standby" mode. Also, since I'm frantically taking measurements while the power light is solid, I'm not paying attention to how it turns off. So I don't know if it slowly fades out or just shuts off.

- The 24V pins on the power board that goes to the inverter always measure 0V.

[retiredcaps]

Re: Getting started with troubleshooting

I guess after I've digested it all, I'll move my questions over there.

Check RB805. It should be around 68 ohms.

[nerdbot]

Re: Getting started with troubleshooting

Yeah, I've been reading through the thread trying to make heads or tails from all that has been discussed in that thread. I guess after I've digested it all, I'll move my questions over there.

Thanks again!

[retiredcaps]

Re: Getting started with troubleshooting

However, when I connect everything back up, the power light still doesn't come on.

In post #4

https://www.badcaps.net/forum/showpo...34&postcount=4

jetadm123 suggests you check out the megathread and the resistor that seems to go bad on this particular monitor.

The megathread ...

https://www.badcaps.net/forum/showth...ighlight=245BW

[nerdbot]

Re: Getting started with troubleshooting

Well, I've got some good news and some bad news.

The good news is that my 204B is repaired and working again.

The bad news is that the 245BW still is not. I replaced all the caps on the power board (except for the big 450V 82uF center capacitor). However, when I connect everything back up, the power light still doesn't come on. When I measured the voltage on the S_B pin on the power board, it still reads around 4.3V. However, I did notice the following:

- With the bezel power button+ logic board + power board are connected, the S_B pin voltage does dip toggle between ~3V and ~4V when I push the bezel power button.

- If I don't connect the logic board, and just measure the S_B pin of the power board by itself, then I get a solid 5.3V

Any suggestions?

[nerdbot]

Re: Getting started with troubleshooting

Here is everything I could see on the labels of the 3 caps in question:

35V 1000uF, 12.5mm x 20mm, 105C
SamWha RD VNA PET

35V 470uF, 10mm x 18mm, 105C
SamWha RD W4E

10V 1000uF, 10mm x 14mm, 105C
SamWha RD W1A PET

[nerdbot]

Re: Getting started with troubleshooting

Also you didn't mention the manufacturer and series of the old caps.

Sorry, the manufacturer of the caps for the 245BW is Samwha. It's a bit late here, but I can get the series of each capacitor tomorrow.

As PlainBill mentions those caps chosen are not low ESR. Even before the Japan situation, both mouser and digikey for some reason are getting low or have no stock on popular low ESR caps like Panasonic FR or FM.

These low ESR caps have a 26 week leadtime according to digikey and mouser.

Maybe you should just change those small SMPS startup caps and see if the TV works. If it works, place your order and wait 26 weeks?

Haha, yeah maybe. Though once I get it back together, I'll be less inclined to take it apart again, but I guess it's better than not having a working monitor for 26 weeks.

[PCBONEZ]

Re: Getting started with troubleshooting

Also you didn't mention the manufacturer and series of the old caps.
-
ESR and Ripple specs vary widely even within the realm of low ESR caps.
Can't do an equivalency check without knowing what the old ones are.
.

[retiredcaps]

Re: Getting started with troubleshooting

None of the first three caps are suitable for this purpose. They are not low ESR caps.

As PlainBill mentions those caps chosen are not low ESR. Even before the Japan situation, both mouser and digikey for some reason are getting low or have no stock on popular low ESR caps like Panasonic FR or FM.

These low ESR caps have a 26 week leadtime according to digikey and mouser.

Maybe you should just change those small SMPS startup caps and see if the TV works. If it works, place your order and wait 26 weeks?

[PlainBill]

Re: Getting started with troubleshooting

None of the first three caps are suitable for this purpose. They are not low ESR caps.

How much clearance do you have? This one would be ideal if you can accommodate the extra height (25mm).
35V 1000uF, 12.5mm x 20mm, P12405-ND

It is not necessary to match the dimensions of the caps; they must fit the available space, that is all.

PlainBill

[nerdbot]

Re: Getting started with troubleshooting

Hi guys,

I've been practicing soldering and desoldering on old components, and I think I'm ready to order the replacement capacitors and take a stab at it.

For the most part, I've been able to identify the right capacitors I need for both the 204B and the 245BW. However, I had a question about a few of the replacements. I've listed the capacitor specs (voltage, capacitance, dimensions) and the digikey part # of the replacements I picked.

(When taking my measurements, I assumed the height of a capacitor was just the cap itself, from the top to the base where the leads come out)

Original Cap: 35V 1000uF, 12.5mm x 20mm, 105C
Replacement Cap: Nichicon VZ (493-1322-ND)
Is the VZ series OK? I didn't see it listed in the "What capacitors should I buy?" thread. This is the only match I could find that was rated for 105C temperature.

Original Cap: 35V 470uF, 10mm x 18mm, 105C
Replacement Cap: Panasonic NHG (P5554-ND)
Similarly, is the NHG series OK? There are a few other options that fall under the right dimensions (all of them are 10 x 16). I should have room to accommodate 10 x 20, and if so, I can get Panasonic FC.

Original Cap: 10V 1000uF, 10mm x 14mm, 105C
Replacement Cap: Panasonic NHG (P5521-ND)
Same situation as above. If I go up to 10 x 20, I can get Panasonic FC instead of NHG.

Original Cap: 450V 82uF, 30mm x 22mm, 105C
Replacement Cap: Panasonic TS-ED (P11695-ND)
This is the big capacitor in the center of the board, and the label on the capacitor says "450wv". I assumed that's the same as "450V"? The replacement cap is 25mm tall so I'm concerned that this might be a bit too tall, but didn't see any other options. Also, this cap is listed as "Radial, Can - Snap-In". Is this still an appropriate replacement? Finally, this board has been unplugged for over a week now. Is it safe to remove, or do I need to discharge it?

Lastly, a few of the capacitors have some solid brownish yellow "gunk" on them (you can see it in A-front.jpg in my earlier post). What is this stuff and how do I remove it so I can remove the capacitors?

[nerdbot]

Re: Getting started with troubleshooting

I would certainly recap the power supply and the inverter. The caps on both of these deal with high surge currents which will age the caps rapidly. The caps on on the signal board are generally on the output side of analog regulators, and don't deal with high surge currents.

If you wish, you can order a complete set of caps. My reservation is you are inexperienced at this. Recently we had a multi-page thread where someone recapped his power supply and it stopped working. It turned out he had managed to break a trace, disabling the main supply. I would rather you take small steps on this project. But it IS your call.

PlainBill

I think I'll take your advice - replace the 3 capacitors first, and if that's successful and I feel a bit more confident, I'll replace the others as well. I also have the capacitors on my 204B to replace, so I'll be getting a lot of practice one way or another. If I can get even 1 out of the 2 monitors working again, I'll consider it a huge success.

Thanks again PlainBill, and everyone else, for your help! I'll let you know how it goes.

[PlainBill]

Re: Getting started with troubleshooting

Ok, I wasn't sure if that brown color on the pins indicated damage, overheating, or what not. Good to know!




When you say "complete set", do you mean for the power board, or for all 3 boards (power, logic, inverter)? I count 10 more capacitors on the power board (on top of the 3 we've already identified) and 2 capacitors on the inverter board. As for the logic board, I'm not sure if those round silver things are capacitors or not?

I would certainly recap the power supply and the inverter. The caps on both of these deal with high surge currents which will age the caps rapidly. The caps on on the signal board are generally on the output side of analog regulators, and don't deal with high surge currents.

If you wish, you can order a complete set of caps. My reservation is you are inexperienced at this. Recently we had a multi-page thread where someone recapped his power supply and it stopped working. It turned out he had managed to break a trace, disabling the main supply. I would rather you take small steps on this project. But it IS your call.

PlainBill

[nerdbot]

Re: Getting started with troubleshooting

The coating is causing the dark color in the pins, and can make it difficult to get a reliable reading, as you have already noticed. It's annoying, but nothing that should seriously impede troubleshooting. Just remember if you make a measurement that indicates something (a resistor) is open, it may be the coating preventing good contact.

Ok, I wasn't sure if that brown color on the pins indicated damage, overheating, or what not. Good to know!

If I had this monitor on my workbench I would be ordering a complete set of replacement caps. Once you get the monitor working you should seriously consider doing that.

When you say "complete set", do you mean for the power board, or for all 3 boards (power, logic, inverter)? I count 10 more capacitors on the power board (on top of the 3 we've already identified) and 2 capacitors on the inverter board. As for the logic board, I'm not sure if those round silver things are capacitors or not?

[PlainBill]

Re: Getting started with troubleshooting

Are you referring to the brown/rusty looking substance on the logic board pins? Or are you referring to the darker color of the power board?

The coating is causing the dark color in the pins, and can make it difficult to get a reliable reading, as you have already noticed. It's annoying, but nothing that should seriously impede troubleshooting. Just remember if you make a measurement that indicates something (a resistor) is open, it may be the coating preventing good contact.

Yeah, this particular monitor was either on or in standby all the time. I guess I should get in the habit of turning it off...

Not strictly necessary. I'm pointing out the darkened color because of what it suggests - caps may be dodgy because they have been lightly toasted. It also may indicate air circulation wasn't particularly good.

If I'm reading the values correctly, then:

- Small, left most capacitor = 50V, 22uF
- Larger, center capacitor = 50V, 47uF
- Small, right most capacitor = 50V, 2.2uF

Thanks, PlainBill

Here are the recommended replacements. The first number is the Digikey stock number; the second is the manufacturer's (Panasonic) part number. If you live in the USA I recommend Digikey because they have a USPS First class Mail shipping option that would cost about $2.50 for these parts. The caps range in price from $.31 to $.34 each.

- Small, left most capacitor = 50V, 22uF P12927-ND EEU-FM1H220
- Larger, center capacitor = 50V, 47uF P10321-ND EEU-FC1H470
- Small, right most capacitor = 50V, 2.2uF P10313-ND EEU-FC1H2R2

If I had this monitor on my workbench I would be ordering a complete set of replacement caps. Once you get the monitor working you should seriously consider doing that.

PlainBill

[PlainBill]

Re: Getting started with troubleshooting

Apologies if i am barging in without knocking..

Correct me if i am wrong but does the
1) 8 pin IC (with the Pin 6 missing) marked A6159?
and
2) 16 pin IC (12 o'clock of the Big capacitor) marked MC33067P?

if yes then
1) is Flyback Switching Regulator STR-A6159
2) is MC33067P - HIGH PERFORMANCE ZERO VOLTAGE SWITCH RESONANT MODE CONTROLLERS - ON Semiconductor
and i believe this is what PlainBill is referring to as the SMPS controller..

datasheet here"

Just happen that I just did a Samsung TV with ALMOST identical PS board... but i could be WRONG as well..

For the most part you are correct. Thanks for identifying the ICs. Both are SMPS controllers, although they work in slightly different ways.

At this point the STR-A6159 is the focus of my attention - it is part of the Standby power supply. The output of the standby regulator is obviously wrong, now it's a matter of fixing it.

PlainBill

[newbie1]

Re: Getting started with troubleshooting

Apologies if i am barging in without knocking..

Correct me if i am wrong but does the
1) 8 pin IC (with the Pin 6 missing) marked A6159?
and
2) 16 pin IC (12 o'clock of the Big capacitor) marked MC33067P?

if yes then
1) is Flyback Switching Regulator STR-A6159
2) is MC33067P - HIGH PERFORMANCE ZERO VOLTAGE SWITCH RESONANT MODE CONTROLLERS - ON Semiconductor
and i believe this is what PlainBill is referring to as the SMPS controller..

datasheet here"

Just happen that I just did a Samsung TV with ALMOST identical PS board... but i could be WRONG as well..

[nerdbot]

Re: Getting started with troubleshooting

That causes the brown tint on the bottom, and can cause problems making reliable contact.

Are you referring to the brown/rusty looking substance on the logic board pins? Or are you referring to the darker color of the power board?

This isn't to the point I would suggest junking the board, but does indicate something about the history of the monitor - it saw a lot of use, and got quite warm.

Yeah, this particular monitor was either on or in standby all the time. I guess I should get in the habit of turning it off...

What are the voltage and capacity of those? I don't have a good idea which one would be responsible, but at about $.30 each, it seems logical to replace all three.

If I'm reading the values correctly, then:

- Small, left most capacitor = 50V, 22uF
- Larger, center capacitor = 50V, 47uF
- Small, right most capacitor = 50V, 2.2uF

Thanks, PlainBill

[PlainBill]

Re: Getting started with troubleshooting

Which board is showing signs of overheating? I'm assuming you mean the logic board since those pins are looking brownish.

I saw what appears to be an S_B pin (just to the left of the PSON pin), and I tested that voltage and, depending on how steady my hands were, between 3.5V and 4.3V.

The PSON pin measured between 0.6V and 1.4V. I noticed though that if I had a voltage over 1.0V, it would often slowly decrease until it reached 0.6V or 0.7V.

I tested it anyway, it measured at 160V.

Well, we have a smoking gun - or at least the odor of gunpowder. First, a few points. The bottom of these boards have been coated with some sort of conformal coating. That causes the brown tint on the bottom, and can cause problems making reliable contact. If you look at the lower left corner of the top view of the power supply board you will see what I would call a normal PC board. If you look at the board just above and to the right of the large capacitor you will see it is several shades darker. There are other spots with a similar appearance. This isn't to the point I would suggest junking the board, but does indicate something about the history of the monitor - it saw a lot of use, and got quite warm.

The pin you tentatively identified as S_B is definitely the standby supply, and it is not behaving properly. I would expect a steady voltage (probably 5 Volts) at that point. And that leads me to the smoking gun.

Referring to the picture of the top of the power supply, directly below the large cap is an 8 pin IC (with pin 6 missing). That is the power supply (SMPS) controller. Below that IC are three small electrolytic caps. The erratic voltage and the 'baked' appearance of the board leads me to suspect one of the caps is bad. What are the voltage and capacity of those? I don't have a good idea which one would be responsible, but at about $.30 each, it seems logical to replace all three.

PlainBill