Panasonic TC-P58S2 troubleshooting

[DIYD80]

Hi all--need some feedback on my troubleshooting logic:

My mother in law received a lightning strike near her house, which fried a seemingly random mix of electronics (microwave oven, TV, computer, telephone, etc.). Most of the stuff is relatively small and cheap to replace, so I am in no hurry to tear into it. The plasma TV, though is huge, and was working fine before the lightning, so I thought I would take a poke at fixing it.

Anyway, immediately after the strike, the set showed absolutely no sign of life (I have confirmed that I am getting 120vAC to the power supply boards). No "standby" light, nothing flashing, etc.. I searched for the conventional wisdom, and the conclusion I came to was that in a "no power, no signs of life" condition such as I had, that the probable culprit was the power supply board(s). I had a good look at them, and each had a bulging 250 V 1000microF capacitor, so I thought I had found my smoking gun. I unsoldered both of these and checked their capacitance with my Fluke, and they were each reading ~886 microF, and seemed to still be functioning.

I had no luck finding replacement caps, so just bought two complete (used, but reportedly functional) boards on eBay for $50 and installed them. Still no sign of life. It looks to me like the wiring from the on/off switch goes to the main logic board, and the power supplies get the "on" signal from there. Now it occurs to me that there is low voltage "standby" power coming from the power supply board to the main board and processor all the time, and this would likely provide a direct path for the lightning strike right to the microprocessor.

So...lost cause? The TV is almost 10 yrs old, and new TVs go pretty cheap these days. Any suggestions on how to proceed?

[budwich]

Re: Panasonic TC-P58S2 troubleshooting

well, did you check for the standby power? There is usually a number of voltages on the power board (2 boards???) Pictures of the back of the set with everything connected is likely a starting point along with close ups of the power board(s).

[DIYD80]

Re: Panasonic TC-P58S2 troubleshooting

Thanks for the response. Attached is a pic of the two power supply boards from a releative close-up. I can see that there are several two-pole connections that go off to supply the other parts of the TV, but none of them have any marking besides things like "P11" indicating what it connects to, but nothing more. I haven't been able to find any documentation specific to this set, so am unsure of where that standby power should be coming off the power supply.

Was hoping for a a quick and dirty resurrection resulting from replacing the power supply boards. That not happening, it is logical to make certain that the replacment power supply boards are functional, but having no literature to describe what to measure under what conditions, I am feeling my way forward.

So I am inclined to assume that the replacement power supply boards are functional as advertised by the seller, at which point, I have to assume that still more of the interior of the TV took a hit from the lightning strike, and it could be that every board has been rendered DOA.

[budwich]

Re: Panasonic TC-P58S2 troubleshooting

:-( I hate when the labeling so "poor". It would still help if you photo the complete tv backside with all the boards attached so people can understand what you are up against and provide some suggestions. Also in terms of voltages, check labeling on other boards as a "cable is a cable" and you only need to know a point / pin at one end to know whats up at the other.

You might be stuck with slowly working thru the HOT side, strategically checking voltages along with way towards some components (ie. diodes, ic, transformer, etc) to see if anything jumps out. As for the age of the set and its "worth" in terms of time and effort, while it depends on you. Some people like a plasma picture and since they aren't made any more, repair is the only option (buying second hand the other).

Further: a quick scan of manuals shows this... hopefully it has something you can use... of course the database / site is only as good as the owners / contributors make it.
https://www.manualslib.com/manual/83...s2.html#manual

Still further: not sure why I didn't ask earlier... you checked any fuses on the boards (FXXXX or something like that) especially on the power boards.

[budwich]

Re: Panasonic TC-P58S2 troubleshooting

Looking at the linked manual, it does appear to provide the powering schematics at the A board which is good because you should be able to follow those back to the power boards.

[DIYD80]

Re: Panasonic TC-P58S2 troubleshooting

Wow--that linked manual is just what I needed. This should help a lot.

Yes, I did check anything that looked like a fuse, and all were intact.

[budwich]

Re: Panasonic TC-P58S2 troubleshooting

"all were intact"... what does that mean? You can't check them visually, you need a meter.

[DIYD80]

Re: Panasonic TC-P58S2 troubleshooting

Correct, all fuses were checked with a meter, and all in good shape.

[jetadm123]

Re: Panasonic TC-P58S2 troubleshooting

Assuming that one/both replacement power supplies are good, then there's the possibility that the mainboard is bad. If the TV is getting it's signal from an antenna or cable box, then lightning could have taken that path and fried the board. As suggested above, good photos of how all the boards are connected might help determine which wiring harness is feeding the standby voltage. You might also check underneath the power board to see if any of the wiring pin descriptions are silkscreened on the board.

[DIYD80]

Re: Panasonic TC-P58S2 troubleshooting

The maintenance manual was key. It identified the wiring harness that carries the 5v standby power from the power supply to the main ("A") board. I confirmed that the 5V was making it to the main board. Made a visual inspection of the main board front and back and can see no physical evidence of damage. No fuses on that board.

I guess I am ready at this point to assume the main board (and who knows what others) got a good dose of static electricity and is nuked. Will probably throw in the towel.

[budwich]

Re: Panasonic TC-P58S2 troubleshooting

:-( rather disapppointing. are you sure you want to give up that easy. Are you looking at stb5v or sub5v? I guess my question is why did you start on this "journey" in the first place.... were you hoping for a "easy fix" of a blown fuse? Almost all other issues were probably a bit deeper than that. Don't take it wrong, thought you were actually going to try and locate a fault component part and possible replace it unless there was significant issues (complete board gone... that cost $$$). With the manual, I would think you can get a little further... maybe. Since you have two other boards... is there a difference with the "5v discovery". Note: there are other voltages that need to be there besides 5v.

Can you list by reference number all the fuses that you checked as "all fuse checked with a meter" only indicates those that you checked are good but does nothing to indicate that you checked all fuses. :-)

[DIYD80]

Re: Panasonic TC-P58S2 troubleshooting

Well, I appreciate the responses this thread has gotten. I would say that I am throwing in the towel earlier than I normally might (which is why I am surrounded by half finished projects), but there are some logistical issues that make working on it painful (ie., it is at my mother-in-law's house which is a 40 mile round trip). Plus, my diagnostic tools are limted to a VOM, so getting very deep into it would be a challenge.

I wish I had had the manual before pulling the original power supply boards, might have determined that they didn't need to be replaced. For the fuses, I checked F201, F501, F601, F602, F801, F802, and F901. All of these were on the power supply boards. Didn't find any fuses on the A board.

Anyway, looking at the A board, I see mostly surface mount components and ICs. Literally everything else in the console also has ICs. I am haunted by the recollection in the early days of home computers back in the 80's where the conventional wisdom dictated that you ground yourself prior to even touching a keyboard to minimize the risk of ESD wrecking your computer. I figure if the A board is wrecked by the lightning, then it is easy to imagine many other ICs being potentially affected as well. Had this TV just spontanesously failed one day, I think I would have much more hope that a single failed component (or even a single board) could be identified, but in this case, knowing that the A board took a big enough hit to wreck it leads me to suspect that everything connected to that board with ICs may well be wrecked also.

[budwich]

Re: Panasonic TC-P58S2 troubleshooting

no problem, logistics suck especially with big tvs... not easily carted to "work areas" and such.

NOTE: lightning could have taken out lots of stuff BUT it could also have just caused a "singular" issue... especially since you don't see "smoked components".

There have a been a few other threads with some similar failures (ie. no standby) in which the owner track thru the powering and found nothing bad there. Then moved on to the A board as the standby light / power originates there. Ultimately it was found that there was an issue with an ASIC that did the low voltage conversion. Instead of replacing the ASIC, the board was replaced and the tv brought back to life thereafter.

You only need VOM to check a couple of things on the A board specifically related to the standby circuit. I suspect that you would get "lucky" thereafter... of course, not knowing how much an A board is for this set and / or can be found.