Samsung P58C8000 ~ Power Supplies have failed (2)

[kca]

Hello all ~

I picked up this Samsung 58" plasma the other day and both power supply boards (the original and another one the owner bought online and tried) obviously blew out the exact same transformer. I will attach pictures soon.

My questions are:

Does this look familiar to anyone and does it indicate a fault on another, specific board?

Seems to me like it could not be a coincidence, but rather that I have to track down a separate faulty board (and hopefully not boards) that have defects. I already went ahead and bought a new power supply board but will not put it in until I solve the mystery of what has caused 2 prior PS boards to blow in the exact, precise same manner.

Thanks in advance for any insights anyone can provide.

By the way, please ignore the picture orientations and the upside down dog in particular. And, I only included here the up-close images of the "New Board", meaning the replacement board that the owner purchased online. But know that the original board has the exact same burn marks on the exact same wire + transformer. And, if anyone knows a trick to keep the pictures upright when uploading, please let me know. Sometimes it does and sometimes it doesn't.

~ kca

[R_J]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

To me it looks like there was a poor solder connection on that pin that arced, It is one of the pins that does not have a rivet. If the transformer was bad I doubt it would have arced at the connection to the pc board. Clean and resolder the connection, check Qs802 & Qs806 for shorts, The board might still work??

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

I was thinking the same thing.

But very odd that two boards would fail in the exact same place, don't you think?

I can and will take a couple of pictures of the backs of these PS boards and post them. That might help with the diagnosis.

As I mentioned, I went ahead and purchased a new PS board yesterday and it will arrive in a couple of days. Under $40. My plan was to try to inspect all of the other boards with the PS still out, and if those all check out then plug each board in along with the PS one at a time. Is there a better (safer) way to proceed, so I don't blow out this 3rd PS board as well?

[R_J]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

I would check & resolder all the pins on the transformers, and diode/transistors mounted to heat sinks.
The BN44-00333A schematic looks close, although some of the components are labled different

[tom66]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

That might not be a failure. Just looks like it got warm around there. Typical underengineering by Samsung but probably ok (if the board does not work, something else is probably wrong)

A blown transformer would show in the insulation tape or not at all. Hard to tell really. But pretty darn rare.

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Thanks. I’ll do that.

I’m going to be working with the new board I just ordered, primarily, but are you saying that these two other boards can both be rescued because they only arced and did not truly damage the transformers themselves?

I suppose just those transformers could also have been replaced with new ones, but I am thinking it best to start over with a new PS board from a reputable company.

I didn’t ask the guy I got it from if the 2nd PS board he bought blew out immediately or after a period of time. I’m assuming immediately, but will try to find that out.

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Thanks tom66 ~

I think you just gave an answer to my prior question.

I was assuming that a faulty other board (X, Y, Logic, etc ...) was the culprit that was causing this very specific PS transformer overload. But I think I hear both of you saying that is actually UNlikely. Is that true?

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Here are 6 pics of the boards in question, fronts and backs.

The first 3 are of the original board, with a prominent burn mark.

The final 3 images are of the new, replacement board that the owner purchased online and installed himself.


Any telltale signs there?

[tom66]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Yes, pretty unlikely.
Looks like the solder joint may have been bad.

[vinceroger69]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Maybe worth putting some sort of insulation on that area on the metal chassis where the burn mark is as may stop it happening again.

[R_J]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

You can see the poor solder connection in this picture. Thats all that happened. The connection went bad and it started to arc. Resolder it and it will never happen again.
I bet the boards are fine once the connection is repaired, also resolder that pin on the new board to prevent it from happening on it too.

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Good idea. I have a thermal pad that will work nicely there over that burn mark.

I did notice that Transformers #1, #2, and #3 (counting from the top of the board to the bottom) all have the same rivet / non-rivet pattern down the left hand side of the transformers. Each has 4 legs there, and Legs 1, 2, and 4 all have the rivets. Leg 3 is rivetless on all 3 of these transformers. Only on Transformer #1 has that leg experienced the arc + burn.

Hope the attached picture is clear enough to show that. This fact is one element leading me to think that some other defect elsewhere in the set was putting particular stress on this isolated transformer (on both PS boards) and furthermore on these isolated legs.

They are clearly non-riveted by design. Transformer #4, in fact, has two purposefully non-riveted legs.

[R_J]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Stop over thinking it, It was a poor solder connection, some engineer made a saving by not putting a rivet there, the connection did not get enough solder, the transformer vibrates at its frequency and over time the connection went bad. it happens all the time.

[budm]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Poor soldering works, I have seen so many bad soldering works on those through hole rivets also.
https://www.badcaps.net/forum/attach...1&d=1522948819
The wire of the transformer winding also look like poorly wrapped and soldered to the transformer's leg in the pictures.

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Found out this evening from the previous owner that the replacement board he purchased gave out immediately. No overt sound or smoke, but he recalled that no picture ever appeared. So, it likely blew right after he installed it.

I'd rather overthink than underthink it. However, the next logical step does seem to be to clean and resolder all of those legs on that transformer and probably on the three other transformers as well while I'm at it. Then power it up and see what happens. Will do that tomorrow.

Will use the thermal pad over the burnt area on the metal panel. Will also introduce one board at a time.

Thanks to everyone who helped assure me of the best approach at this point in time. I'll post again when I learn and know more.

~ kca

[tom66]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

It is really really rare that the X- or Y-main will cause the board to fail immediately. They have overcurrent, short circuit and various other types of protection systems that are unlikely to allow it to fail immediately. Whilst not impossible for it to fail as described, it is more likely something else is wrong.

[mmartell]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Keep in mind that with mass produced items come mass produced problems. They could have went their whole production run supplying too little solder to that particular connection.

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Thanks. And, I suppose there is also the small possibility that the replacement PS board was already damaged when he purchased it online and he installed it. He was inexperienced, but very sharp, so unlikely that he missed that burn mark on the backside.

He also purchased and tried a new main board and apparently 2 different logic boards. That's when he got frustrated and gave up on it. I have all three of those boards in my possession now. None look visibly damaged.

Note: I haven't done anything with these 3 “spare” boards yet (see images) in terms of researching potential compatibility and structural issues. That's part of today's work.

I'll get some hi-res, up close pictures of all the boards that are currently in the tv once I have the back panel off again. Any suggestions or insights in the meantime are very much welcomed. Thanks, everyone.

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

By the way, great little video link here for anyone trying to troubleshoot these types of Samsung plasmas in particular:

https://youtu.be/JjrwTZC5nVg

[kca]

Re: Samsung P58C8000 ~ Power Supplies have failed (2)

Hello all ~

About to add the solder in order to repair and touch-up these connections.

In your collective opinion, should I solder every leg both the back on the back of the board and the front as well? I just want to make sure that adding a touch of solder on the front side of the board to and all transformer legs is tantamount to re-creating the rivet effect.

Also, budm mentioned above about the shoddy soldering on the transformer wires. I got my new board in yesterday and the quality of its soldering is about the same as on the two previous boards. Meaning, mediocre. (See images below of this latest board I just purchased).

Assuming that I add some solder to this wiring wherever the copper seems to be showing through inappropriately, is there anything I should take note of and apply? No special type of solder needed in such a circumstance, is there? Or placement of the solder itself?

Note: I'm going to take one of the two damaged boards and fix it up / resolder it first. Kind of use that as an experiment, before throwing the board I just purchased into the mix.