Panasonic TC-P50G20

[thumper69]

Many threads on this tv but i do not see anything on my issue. Visual-10 blinks after turn on. Using panasonic repair manual i looked for short on 15 volt sc board and ss board. Resistance on both sc line and ss line seemed to be normal as in over 1k ohm reading. I read no rise in 15 volt line with meter connected when i turned on set. unplugged sc20 with meter connected turned set on observed 15 volts until shutdown circuit kicked in. my conclusion is bad sc board as per manual. AM I MISSING ANYTHING. Also what is the best setting to have your meter set to when doing the resistance checks. Any help would very much appreciated.

[thumper69]

Re: Panasonic TC-P50G20

Someone must have some thoughts on this.

[budwich]

Re: Panasonic TC-P50G20

you need to investigate the sub voltages (5, 3.3) to see what they are doing. Further, the SOS may not be reporting the right code as the A board may be "confused".

what is the history of the set? How did it get to its present state?

[RJARRRPCGP]

Re: Panasonic TC-P50G20

Another wild goose chase, LMAOO!

[thumper69]

Re: Panasonic TC-P50G20

The history of the set is from the time it was new to sudden failure two weeks ago. Worked in the evening not in the morning. All voltages present except 15v when powered on. 15 volt present with sc 20 removed.

[thumper69]

Re: Panasonic TC-P50G20

Why a wild goose chase RJARRPCGP.

[RJARRRPCGP]

Re: Panasonic TC-P50G20

Why a wild goose chase RJARRPCGP.

Because of what budwich said...

[thumper69]

Re: Panasonic TC-P50G20

Assuming the A board is confused is there a reset of the board as far as the sos is concerned.

[budwich]

Re: Panasonic TC-P50G20

another question for you... are you going to be trying to repair a board or replace? Just wondering.

"my confusion" comes from the troubleshooting guide which shows / list possible outcomes of some tests and flashes that you have seen / read thru (also). One of the last items listed is "wrong diagnostic by the A board".... which of course is last in the list but still plausible if others check out.

In my limited experience with the 50s30 (which I have not fixed the sc board after a few attempts... with obvious shorted IBGT), after a first fix attempt and during checks prior to full powering of all card... one of the tests was to power up the system with sc20 disconnected along sc50 shorted and the sc to su/sd disconnected, the SOS then reported a flash code 8. Subsequently, after checks and plugging everything up, the set worked for a bit but ultimately took out the IGBTs again. I replaced failed components and tried checks again and subsequent power up. With either the sc20 disconnected or connected, I got 8 flashes... but didn't find anything blown (yet) and have done similar checks like you in and around the 15v and other areas.

I could find anything on a reset of the A board, so I decided to unplug the sc20, and all power feeds between the P board and the A/SS (ie. p6, p11, and p35) hoping for a "miracle reset" (ie. assuming any cap's will drain down, etc). After letting that set for a while, replugged everything back, now I sit with 6 flash. No sure if the A board has "reset" but something changed in just cable unplugging / plugging.

Your 10 flash code doesn't give much in terms of troubleshooting past "replace A" or "replace p".... hence my question. Your "checks / tests" appear to point more at the SC board since isolating it (sc20 disconnect) seems to allow your 15v to come up.

You asked previously about meter settings... if your meter has a "buzz/continuity" setting... this would be best for checking for shorts as then the meter by-passes some of the measuring circuitry and you will get a quicker response if you touch a "short".

Still further, if you look at the guide, you can see the pins which go from the A board to the SC board via the SC20 (29/30)... you can test to see if those are shorted at either A or SC.

Hope I haven't cooked your goose.... :-) sorry for the long post.

[thumper69]

Re: Panasonic TC-P50G20

Budwich i think i will either look for a working board or boards or send in for repair. Either way the cost can add up fast. In this case trying to be as conclusive as possible before making a choice. The reason for asking meter question was in most cases probing almost always shows capacitor action which on my fluke meter may seem to show short but you can see the resistance rising quickly which to me indicates a non shorted circuit. I suspect the sc because sc2 shows quick capacitor action rising above a level thst would indicate a short while the sc 20 shows .448 ohms steady. Thank you for your comments.

[budwich]

Re: Panasonic TC-P50G20

I am some what in the same mode... cost... the set I have was recycled and showed up in my house. I don't necessarily want to spend lots to find out it has more problems although I may have contributed to its "down fall" with my repair effort which between possible "fake parts" and soldering technique maybe its "coffin"... but my time is basically free so I plug away for now.

My experience is that the "buzzer setting" is pretty good with metering as an indication for shorts as opposed to the other setting IF you don't know what the circuit makeup is. You can check for yourself by testing a known component like a capacitor and see what happens.

Having said that... I checked my sc board as I only did the "buzz test". Anyways, at the sc2 connector (it disconnected).... buzz shows open while similarly to yours, in resistance mode / auto, the meter jumps to a relatively high reading and then reduced as the capacitors in the circuit charge. Note: the SC2 connector / circuit is high voltage
with large capacitors in the circuit while the SC20 connector is low voltage and likely has small capacitors in the circuit so they may reach "full charge" at first touch and thus give a "solid resistance" reading forth with. Not much help... but I don't think your results point to an obvious SC fault just yet. Based on my SC experience, the SC2 will show an obvious short. Not sure about the SC20 reading... which pins are you taking the reading on?

One more question, in your testing with the guide (page 79) indicates the process whereby you could get either of two results... none of which point at the sc board... :-(
have you tried that test a couple of times... it appears to be some what timing related because of the 15v action... maybe. Your result is always 10 flashes?

oops, I now see that the TS guide I am referring to is for GT models and not G... :-( maybe a big difference.

[thumper69]

Re: Panasonic TC-P50G20

Well Testing was done at the 15 volt output at p11 i believe with sc 20 connected voltage at less than 1 volt than sos kicks in. Testing was also done at the 15 volt line just to make sure it read the same as 15 at p11. sc 20 was disconnected and 15 volt again measured and was normal until sos again shuts the set down i would think because no current coming from 15 volt on sc board. P board generates the 15 volt and than feeds A board which than supplies 15 volts to SC board through a flat cable. If the problem were on the A board i would think removing sc 20 connector would not have the effect of allowing 15 volts to appear on p11. The difficulty is what seems logical is sometimes illogical for some situations based on engineering designs ?

[thumper69]

Re: Panasonic TC-P50G20

I don't have a trouble shooting guide with a page 79.

[thumper69]

Re: Panasonic TC-P50G20

Sitting here thinking about what other possibilities than the Sc. Has there been occasions of the A board sos analysis faulty to the point of shutting down. If so one would think there must be a way to reset.

[budwich]

Re: Panasonic TC-P50G20

you would think... but I haven't seen a "reset procedure". It is some what strange that almost every code has a "wrong diagnostic by the A board", yet no way to get out of that "mode".

My "page 79" indicates "Plug in the TV and press the power switch immediately after the first relay click from the power supply is heard.".... then "Did the number of blinks changed?" If still "10", then replace A. If "14", then replace P.

About your comment about disconnecting the SC20 impacting the result on the 15v... pointing to the SC.... I guess, potentially, it could be that the circuit on the output of the A towards the SC board (some switching component / "buffer") has an issue such that "loaded" it is not able to maintain the 15v but with the load removed, your reading sees the "open circuit" voltage of 15v.... just a guess though.... but there are also other control pins between the sc and A that may be in play also.

[thumper69]

Re: Panasonic TC-P50G20

budwich- i thank you for your input. I spent almost 20 years in the TV repair business and these kind of problems always drove me crazy. You have to have this before you have that. Sometimes the creators of these high tech equipment forget someone somewhere will try to repair without enough documentation without the availability of tech support and sadly not enough parts at a reasonable price. We are left to do our best with parts from ebay or repair services with a wing and a prayer. I applaud those who find a way to keep things working. Never give up, always strive to be better and hope you find the secret poition. More info coming soon.

[budwich]

Re: Panasonic TC-P50G20

how's the "goose"? did you check the 5v at the SC board?

[thumper69]

Re: Panasonic TC-P50G20

Sent SC board in for repair. Results of repair: 14 bad components. Repair was Successful and the tv lives again. most Sc's would throw a 4 blink or 7-8. I think in my case 15 volt supply to sc shorted or so it seemed and vsus main voltage open so sos read 15 volt first. Just a guess. Thanks all for the help.