Panasonic TV-P55ST30 loud pop, display black and 14 blinks

[Tnmg]

Hoping someone can help me. My Panasonic TC-P55ST30 popped on me this weekend before the ACC Championship game. It made a very loud pop noise before the display went out. I pushed and held the power button and it blinked 14 times before repeating. I disconnected the SC board and put power back and it blinks 7 times. I tried checking the boards using the video here: https://m.youtube.com/watch?v=iHBIiRxhe0w

But I must be doing something wrong. I put my meter on continuity and it buzzes everywhere I'm touching. I put one probe on the chassis and one on p1 on the P board and it buzzes. One probe on p1 and one on p2 and it buzzes. Disconnect the cables off of P board and it buzzes taking points at p1 p2 or chassis.

Can someone help me check to see what board is damaged?

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Hoping someone can help me. My Panasonic TC-P55ST30 popped on me this weekend before the ACC Championship game. It made a very loud pop noise before the display went out. I pushed and held the power button and it blinked 14 times before repeating. I disconnected the SC board and put power back and it blinks 7 times. I tried checking the boards using the video here: https://m.youtube.com/watch?v=iHBIiRxhe0w

But I must be doing something wrong. I put my meter on continuity and it buzzes everywhere I'm touching. I put one probe on the chassis and one on p1 on the P board and it buzzes. One probe on p1 and one on p2 and it buzzes. Disconnect the cables off of P board and it buzzes taking points at p1 p2 or chassis.

Can someone help me check to see what board is damaged?

try searching Tc-P55ST30, should give you plenty to read.

Basically I'd say 99.99% your SC board shorted.

I don't know of a P1 on the P board but I suspect you mean pin 1 on P2 or SC2.

If SC2 is shorted then either pin 1 or pin 2 will buzz to chassis as one of those is gnd to chassis anyway and since the other is already shorted to gnd on the board it's the same result.

You lose me with "Disconnect the cables off of P board and it buzzes taking points at p1 p2 or chassis. "

What cables? and where are you measuring?

If you can't explain you could always upload images using advanced, manage attachments.

If you're pressing and holding the power button to generate a 14 blink that suggests to me the TV was locked and had a solid LED?

If so, when you disconnected the SC board and it went 7 blink that's a good clue the SC is the culprit.

You won't like this bit. You need to check the sd & su boards for shorts before you replace the SC just in case.

replace the board bolts as you'll probably find they were loose and arcing.



check out SJ for this model and you'll find the type with spring washers.

you'll need to find someone who can rebuild the SC board, bound to be some on Ebay. If trying to find a board make note of the revision/version of yours, normally there'd be a white label with it , could be TXNSC1PAUU (TNPA5351) no suffix

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Thanks for the quick response. I did take some pictures and added them if it will help.

When the TV popped, the TV had a solid LED on it. I pressed and held the power button for a few seconds and then it flashed 14 times before repeating. I did a google search and found a page but it was cryptic and basically led me to believe the SC board was bad. Then I found the video I linked before and tried to troubleshoot it myself but not sure I'm doing this right.

With everything hooked up initially, I started these checks. From photo 1 with the red oval, I did continuity checks on pin 1 and GND on P2 on the P board. I put the negative probe on the chassis and the positive probe on pin 1 on P2 and GND on P2. Both times the buzzer set off. Then I put the negative probe on pin 1 and positive probe on GND pin and it buzzed.

Then, I disconnected the cable from SC2 to P2. Then, at the P2 connection, I did continuity checks from pin 1 to chassis, GND to chassis and pin 1 to GND. Buzzed all three times.

Next, I disconnected all cables from the P board shown in photo1.jpg. I put all the disconnected cables in green boxes. I tried continuity checks again at P2 the same three ways as above: Pin 1 to chassis, GND to chassis and then Pin 1 to GND. Buzzed all three times.

I tried continuity checks on SC2 at both of those pins and buzzed everytime there as well. I also tried checks with SC2 cable and ribbon disconnected shown in photo2.jpg. I was going to try and isolate the SC2 board but I didn't want to break the connectors in photo4.jpg. How are these things opened up?

This is what I'm confused about. When it buzzes, is that telling me that I have a ground or that I have a good circuit? I thought continuity checks would tell if you had a complete circuit. But a ground is a complete circuit too, so how can I tell if a board is shorted?

Specifically what I don't know is: am I checking the boards SC/SD/SU for shorts correctly? Should I see something different on my multimeter?

I have replaced the board screws in the past with the lock washer like you've attached in the picture and replacing the transistors and diodes is way outside my current skill set.

Thanks again for your help!

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Oh, and the 14 blinks changed to only 7 blinks after I left the cable from SC2 to P2 disconnected and put power back on the tv.

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

I think I need a coffee after reading that.

Look, i have no doubt you have a failed SC.

locked solid is an indication of shorted Vsus (P2-Sc2 is Vsus which is about 200Volts, same is supplied to the SS SS11).

So for the experience, assuming you have not powered this on very recently because residual voltages will exist for a short while at these points.

With everything hooked up, just set to continuity and place a probe either side(measure across the pins) at P2, that's pins 1,2 at P2.

I expect it will beep.

now, disconnect either the Sc2 end or the p2 end of the cable. Repeat the same test.

i expect it not to beep.

The 14 change to 7 with SC2 removed tells me you have shorted Vsus at SC2

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks



Oh, nice work with the images

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

are you by chance reading from a panasonic Training guide like

2011 - FHD Plasma TV
Technical Guide & Troubleshooting Flowchart
2011- Plasma FHD TV – (14th Generation)

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

No, I just googled and started looking at the tech guide.

Ok, I can't find a pin 2 on P2. P2 has a 1 (Vsus) and a 3 (GND). With everything hooked up, one probe on each of these it beeps. Disconnected cable at P2, still beeps.

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

beep = continuity = short or low resitance. i think my fluke anything below 100ohms beeps.

I'm confused with everything disconnected and buzz at pin1, P2 to gnd.

I believe the connector the brown cable goes to is the one to check = Vsus, white one is gnd

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

No, I just googled and started looking at the tech guide.

Ok, I can't find a pin 2 on P2. P2 has a 1 (Vsus) and a 3 (GND). With everything hooked up, one probe on each of these it beeps. Disconnected cable at P2, still beeps.

that would be right, So what p1 & p2 were you referring to?

so if you disconnect the other Vsus line, p11, is it still the same?

What sort of meter do you have? I'm not trusting this continuity bit.

what ohms range do you have or is it auto ranging?

Might be better to measure the resistance across SC2 and then do P2.

If the vsus was still shorted I doubt it would have gone 7 blink. i'd expect no change so i highly doubt the P baord is shorted unless the Ss shorted at the same time of failure.

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Maybe I'm doing this wrong. I put my other meter (digital) on 20k ohm on both pins with everything hooked up. 0 ohms.

I disconnect sc2 cable from P2 and try again. It starts counting up but slowly to 10. 10k I dunno. I stopped.

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Maybe I'm doing this wrong. I put my other meter (digital) on 20k ohm on both pins with everything hooked up. 0 ohms.

I disconnect sc2 cable from P2 and try again. It starts counting up but slowly to 10. 10k I dunno. I stopped.

go with that because that makes sense and is what I expect you to find. So what is the Digital meter, auto or range selected? what's it's max for resistance?

i think we move on, you need a SC or get it repaired

need to check these buffers

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Ok, I guess I was doing this wrong. I got a beep with everything hooked up and it buzzed with 0 ohms. Unplugged and it stopped buzzing with 80k ohms.

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

Ok, I guess I was doing this wrong. I got a beep with everything hooked up and it buzzed with 0 ohms. Unplugged and it stopped buzzing with 80k ohms.

move onto buffers

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

When I check both pins on SC2 disconnected from P2, it stays at 0 and beeps.

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

What are buffers and how do I check them?

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

yes , you'll enjoy this, more resistance and continuity checks. use the digital and I would like to know what it is I'm working with here range wise.

Start with Vfo and have the meter set in megohms, we don't want low ohms or short but as a rough guide over 1.5megohms,

the others I'd have to check but one could be 200k ohms and the other will be megohms and be out of range if your meter is a basic one.

measure resistance between Vfg and each of the others, if a buffer is shorted Vfo i find is always bad or shorted.

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

What are buffers and how do I check them?

Had upload issues, see if you can follow the diagram

[Tnmg]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

I did a quick check of the buffers. I put one probe on the chassis and used the continuity to run through the buffers, or what I think are buffers. I didn't get any buzzers.

Do I go through with the digital in the 2M ohms on each of these connections and take readings? There's a lot of pins I'll probably have to do that tomorrow after work. Thanks again for your help!

I added a photo of what I think are buffers.

[tw2005]

Re: Panasonic TV-P55ST30 loud pop, display black and 14 blinks

I did a quick check of the buffers. I put one probe on the chassis and used the continuity to run through the buffers, or what I think are buffers. I didn't get any buzzers.

Do I go through with the digital in the 2M ohms on each of these connections and take readings? There's a lot of pins I'll probably have to do that tomorrow after work. Thanks again for your help!

I added a photo of what I think are buffers.

you probably missed my post as i was editting but follow that. leave the panel ribbons alone if you can for now, just check the points I've marked on the input side. Forget about chassis earth, it has nothing to do with the buffers.

Remove the SC board, its toast anyway, and probe the connectors at the SD/SU. Check Vfo first and set 2M ouhs and see what we get.

If you can get away with not touching the panel side this will save you some heartache becasue lining those ribbons up again can be tricky.