Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

[Fusionnex]

Hello,

I have been trying to repair my Panasonic TC-P55GT50 after it just decided to up and fail while in use. I got the classic 7 blinking lights, purchased a new Y-Sustain and Y-buffer boards (SC, SD, and SU board) and replaced them only to get the 7 blinking lights again. I tried to troubleshoot further and I disconnected my new SD and SU boards from the SC boards and then connected a jumper SC50, and the panel turned on, but gives a garbled picture. I am not really sure what to expect here, and not sure if there is an issue with these new SD and SU boards or the plasma panel itself. Any help would be appreciated. I have access to a digital multimeter, and was able to determine that my original SU board gave a beep when testing for continuity between ground and a ribbon cable connector suggesting that my original SU board went bad. I've been reading and watching a ton of videos to try and figure this out. I can provide pictures or other things if necessary.

Thanks!

David

[tw2005]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

Hello,

I have been trying to repair my Panasonic TC-P55GT50 after it just decided to up and fail while in use. I got the classic 7 blinking lights, purchased a new Y-Sustain and Y-buffer boards (SC, SD, and SU board) and replaced them only to get the 7 blinking lights again. I tried to troubleshoot further and I disconnected my new SD and SU boards from the SC boards and then connected a jumper SC50, and the panel turned on, but gives a garbled picture. I am not really sure what to expect here, and not sure if there is an issue with these new SD and SU boards or the plasma panel itself. Any help would be appreciated. I have access to a digital multimeter, and was able to determine that my original SU board gave a beep when testing for continuity between ground and a ribbon cable connector suggesting that my original SU board went bad. I've been reading and watching a ton of videos to try and figure this out. I can provide pictures or other things if necessary.

Thanks!

David

New or new used boards? If it comes on with no error with no buffers and sc50 jumped then it's the buffers. have you tried the checks on the new sd/su boards for shorts? Is everything screwed in , all bolts in the buffers to the SC board?
pictures always help but no buffers connected I would not expect any picture or anything normal at least.

[Fusionnex]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

I did an initial check for shorts on the new boards by checking for continuity to ground from all pins on the ribbon cable connector, and that was clear. Are there other shorts I should look for on these "new" boards? I ordered the SD and SU from shopjimmy, and I beleive they are brand new boards. I ordered the SC boards from sears parts, as it was out of stock at shopjimmy. Thanks for the quick reply! The other thing I am noticing, is some caps that seem to be bulging a bit on the power board, I wonder if the power coming in isn’t clean or something. Although with no error codes with the sc50 jumped and the SD and SU boards not plugged in means it couldn’t be the power board right?

Edit: I'm also 100% positive I had all screws put back in place for SU, SD and SC while testing.

[Fusionnex]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

The boards I purchased ran about $35 a piece, my guess is that they were used. I think i may try and get my hands on some new ones even though they are much pricier at $150 and $200 a piece, still cheaper than buying a new tv I guess.

[tw2005]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

This is out of a ST50 guide

Missing or shorted Vsus.
Abnormality of the scan circuit output, the 15V_F, the
scn_pro, and Vscn circuit.
Loose or open Connection between the SC board and the
SU/SD board (SC41, SC42, SC46).
Open or loose connection between connectors SC2/P2
Wrong diagnostic by the A board
Defective panel

In order of likelihood

1. SU/SD 2. SC 3. SS 4. A / Panel

The TV turned on with no error with sd/su removed, sc 50 jumped. Kinda means all other boards are not triggering 7 blinks unless it's a bad panel?

I don't think I'd shell out $300-400 on boards yet. Whatever they supplied if defective they will replace.

See if this ST50 guide helps. start at page 51, I'd read the whole section first, gives some resistance checks for the SD/SU. Also suggests possibility of bad SS can trigger 7 but i have my doubts on what you report.

following the 7 blink flowchart, it says same, isolate sd/su, jumper, power on no blinks, replace sd/su. But make sure the 4 Vfg bolts are in to attach the buffers to the SC or it will fail and 7 blink.

[flocko]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

The buffer test is done between the ribbon sockets and Vfg not common ground? a Vfg test point can be found on the board, this is for boards that are not mounted in the set or to the SC, but as a bench test for suspected faulty or replacement boards before fitting, as a bad SU/SD can and will damage a good SC and in some cases the SS board as well, testing S/hand buffers is a must do, as most will come from a set that had a broken screen, and this will put a short across the PDP and in turn the buffer ICs get damaged ,most sellers will say they are tested and working when in fact there not

[Moreno83]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

I had the same with a plasma. With jumper on SC board and buffer boards removed the tv turned on and stayed on.
Purchased a new buffer board and tested it for shorts and was fine! Inserted the buffer boards and got shorted with 7 blinks on first startup. Ordered 2 new buffer boards and same thing again , again shorted! In my case the panel was shorted.

Hope you can fix the problem!

[flocko]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

I think if you test the SU/SD boards that were in the set when the fault first appears, and there are more than a few shorts on one IC or more then one IC has shorts then it is possible that the PDP is faulty. Normal buffer faults would be one or two shorts.

[tom66]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

If the boards are shorted in the same location, then it can be a panel fault.

Bear in mind it is extremely rare for the panel to have an internal short. Unless it is cracked, of course. Some LG plasmas get damaged ribbon cables which damages the buffer ICs. And very early Panasonic 1080p panels (42" only, 2007/2008 generation) had a problem with pixel contamination causing an small arc-over fault and damaged panel.

[Fusionnex]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

So, I took a look and was able to isolate shorts at pins SU41 pin6 and SD42 pin 2 (labeled vscan in the repair manual) when connected to the SC board, but when not connected to the SC board I cant find any shorts on the SU and SD boards themselves. I completely isolated the SU and SD and jumped sc50 and then powered the TV up with just the SC and everything else connected, and the TV did power up with green lights on the SC and SS boards. This leads me to believe that the SC is good. I definitely was able to find multiple IC's that were bad on the original SU and SD boards, possibly indicating a panel fault. So either the used SD and SU that I was given are faulty, or i plugged them in and the panel shorted the new ones suggesting a panel fault.

[flocko]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

Check the latest SU/SD boards for shorts and compare results with the original boards if they are in the same places that would indicate PDP fault as Tom points out. If there is no match then you have hope that the PDP will be fine ,and possibly the buffers were faulty when you put them in. I hope this will show you the need to test the buffers before fitting, any that do not pass the test can be returned to the seller as faulty

[Fusionnex]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

Check the latest SU/SD boards for shorts and compare results with the original boards if they are in the same places that would indicate PDP fault as Tom points out. If there is no match then you have hope that the PDP will be fine ,and possibly the buffers were faulty when you put them in. I hope this will show you the need to test the buffers before fitting, any that do not pass the test can be returned to the seller as faulty

Definitely great advice. This was my first TV repair. I took electronics apart and did quite a bit of soldering as a kid, and I build my own computers. I should have known better to test them, but as far as I can tell there is nothing wrong w/ the used boards themselves. I just didn't have the experience to test them before putting them in and thought that vendors would be reliable. Very naive of me. I ran a multimeter from the ground screws to the output ribbon cable attachments as per a youtube video I watched and couldn't find any shorts before or after installation. One of the old boards definitely had a short on two different ribbon cables connectors to ground. I am just super new to any sort of TV repair, its definitely been more complicated than I thought initially. Thanks for all the help!

[tw2005]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

This is out of a ST50 guide

Missing or shorted Vsus.
Abnormality of the scan circuit output, the 15V_F, the
scn_pro, and Vscn circuit.
Loose or open Connection between the SC board and the
SU/SD board (SC41, SC42, SC46).
Open or loose connection between connectors SC2/P2
Wrong diagnostic by the A board
Defective panel

In order of likelihood

1. SU/SD 2. SC 3. SS 4. A / Panel

The TV turned on with no error with sd/su removed, sc 50 jumped. Kinda means all other boards are not triggering 7 blinks unless it's a bad panel?

I don't think I'd shell out $300-400 on boards yet. Whatever they supplied if defective they will replace.

See if this ST50 guide helps. start at page 51, I'd read the whole section first, gives some resistance checks for the SD/SU. Also suggests possibility of bad SS can trigger 7 but i have my doubts on what you report.

following the 7 blink flowchart, it says same, isolate sd/su, jumper, power on no blinks, replace sd/su. But make sure the 4 Vfg bolts are in to attach the buffers to the SC or it will fail and 7 blink.

Better clarify my last sentence

But make sure the 4 Vfg bolts are in to attach the buffers to the SC or it will fail and 7 blink.

these bolts are out for the isolation test, but have to be in when the TV is fully assembled normally and powered up. We've had a few now chasing their tails after replacing parts and still 7 blinks, if those bolts are forgotten it will 7 blink.

[Fusionnex]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

Better clarify my last sentence



these bolts are out for the isolation test, but have to be in when the TV is fully assembled normally and powered up. We've had a few now chasing their tails after replacing parts and still 7 blinks, if those bolts are forgotten it will 7 blink.

Hey tw2005

Those bolts were back in when I tested it after replacing the SC and SD SU boards. Its highly likely i was sold a bad SD or SU board is my guess. Thanks for reminding me to check the simple things. I think in the long run I am just going to return the boards I was given and maybe sell off the parts. I'm a bit sad to see the plasma go as it definitely has a superior picture over LED LCD, but I am not so sure I want to try and buy some brand new SU and SD parts, as they are like $150 and $200, and then if the PDP is shorted, and those burn out it would just be $350 down the drain, in addition the $150 brand new SC board bringing the total repair in brand new parts up to like $500. Is there any way to check for a PDP short? BTW thank you for the repair manual, that definitely helped out. Everything still points to a bad SU/SD or PDP.

[billyac]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

So, I took a look and was able to isolate shorts at pins SU41 pin6 and SD42 pin 2 (labeled vscan in the repair manual) when connected to the SC board, but when not connected to the SC board I cant find any shorts on the SU and SD boards themselves. I completely isolated the SU and SD and jumped sc50 and then powered the TV up with just the SC and everything else connected, and the TV did power up with green lights on the SC and SS boards. This leads me to believe that the SC is good. I definitely was able to find multiple IC's that were bad on the original SU and SD boards, possibly indicating a panel fault. So either the used SD and SU that I was given are faulty, or i plugged them in and the panel shorted the new ones suggesting a panel fault.

I had the exactly same thing with TC-P55ST50
Not sure what to do next as SU/SD now show no shorts but getting 7 blinks again (no blinks when isolated)

[tw2005]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

Regarding the following:
..."As for the SC50, disconnect, the 3 white connectors from the SC to the SD/SU. remove the 4 earth screws at the buffer boards. Jumper SC50. Turn the TV on and confirm it starts normally, no blinks and also if you view the TV from the rear on both the sustain boards there should also be an onboard green LED lit. This will confirm both boths are good and running."

I am troubleshooting a TC-P55ST50. Does the quoted procedure above confirm the SC is good and SU or SD is not?
Here's the history of what I did:

1. TV went pop and started displaying 7 blinks.
2. When thru troubleshooting flowchart from web
3. Flow told me SD was bad ( I think- bottom one)
4. Replaced that board from ShopJimmy.com
5. It displayed a menu rectangle middle of screen with white horizontal lines near vertical center of screen (maybe some ribbons not seated properly?)
6. After a few seconds back to 7 blinks.
Ran thru flow again - isolated SU/SD and no blinks- says change su and sd

I am hearing that I should replace SU, SD and SC but I am not sure.

- with Grounds removed from SU/SD and white connectors lifted (3) and isolation jumper in place no blinks and green light on SC

What I am not sure of is this:
If White connectors are in place when I check continuity from floating ground to pins 2 and 6, they both show short on one or the other but no shorts when connectors lifted- checked from SC ground to pins 2/6 or from SC/SD grounds to pins 2/6
Also, as per a youtube video, before replacing the SD board, I checked continuity from floating grounds on SU and SD to all ribbon connections and got some shorts on SD confirming that it was bad SD as the flowchart also indicated.
Now (even after 7 blinks returned) I see no shorts on the new board

But still 7 blinks and not sure what to do

I cannot find exact service manual for this TC-P55ST50
Don't see it here
http://www.toms-service-manuals.com/...h=Submit+Query

Does anyone know a compatible manual I can use?
The one I have been using for flowchart is
Model :TC-P50ST50＊ (America)

so the manual your using is it this one?

2012 Plasma TV Troubleshooting Guide
2012-Plasma FHD TV – ST Series (15th Generation)
TC-P50ST50TC-P50UT50

First step is disconnect SS11 and see if it goes 8 blink = SS board, 7 = re-connect then continue.
Then disconnect Sc20, 7 blink = A board, 8 = re-connect sc20 continue next slide.

with the sd/su isolate and Vfg bolts out, sc50 jumpered = no blinks that normally means the Sc is ok.

isolate the white connectors from SD and SU

repeat resistance test on SD/SU but I want you to check between the VFG points on the actual buffer boards and these pins looking for low resistance or short. these points can read in megohms when good.

SU41 pin 8 - vfg
SD42 pin 1 - vfg

report readings back please

And i read this

Note: Change the SU and SD boars together even if only one is found to be defective.
Slide 20

It is possible a bad panel killing buffers and 7 blink too

[billyac]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

The title on the manual I have is below.
It's the closest I can find.
It's for TC-P50ST50
Mine is TC-P55ST50 Oct 2012
At the bottom of the sticker it says TC-P55ST50-2
s# mg22860129

Technical Guide
2012-Plasma FHD TV - ST Series (15th Generation)
Model : TC-P50ST50 * (America)

[billyac]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

Oops, just noticed you sent proper manual- Thanks!!

[ljintexas]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

Buffers can kill other boards..I learned the hard way. TW2005 knows these Pannys well.

[billyac]

Re: Help Reparing Panasonic TC-P55GT50 7 blinking lights, Narrowed down to SU or SD

so the manual your using is it this one?

....

repeat resistance test on SD/SU but I want you to check between the VFG points on the actual buffer boards and these pins looking for low resistance or short. these points can read in megohms when good.

SU41 pin 8 - vfg
SD42 pin 1 - vfg

report readings back please

TW, thanks for the info.
I will do that test and let you know.
It's a friends TV (his place) so may take a bit of time.