Panasonic P50ST50B plasma TV: 13 blinks

[faenil]

Hi everyone,

disclaimer: I am a newbie at electronics, trying to learn as I go This is my first troubleshooting experience.

My Panasonic P50ST50B has stopped turning on a couple of months back, and I am now trying to understand what happened and if there is a way to fix it.

The red LED turns on when you plug the TV, pressing buttons on the remote will make the LED flash green fast for a few seconds.

After 2-3 minutes of no activity, the PSU clicks twice and the LED turns red again and blinks 13 times.

According to the technical manual,
"This condition can happen when the internal communication of the Main processor
and the Standby microprocessor within the PEAKS-LD4 IC is interrupted.
It could take up to 3 minutes after the TV is turned on for this condition to occur."

The display never turns on.
A few weeks ago I could get it to turn on every once in a while.
When that happened, it would display the Panasonic logo and get stuck there.

I measured voltages at P6, the results are the following:
- TV plugged to AC but forced off: all pins 0v except pin 6 at 4.5v (I guess this is an error in the multimeter, based on other posts on this forums)
- After pressing power button:
pin 6 4.5v
pin 7 3.0v, fixed
pin 10-11 15.80v
pin 13-15 2.15v ( ??? )
- After 2-3 mins, i.e. once the TV goes into shutdown and starts blinking red 13 times:
Not sure about this one (multimeter isn't working at the moment)
I think it was just pin6 4.5v and 10-11 15.8v


More info:
- I checked the top fuse on the PSU board (the one close to the input). There is continuity (so it should be fine, right?)
- pin 1 of P6 is always at 0v, i.e. the Panel ON signal never comes (as far as I could see)
- I verified that IC8714 has 3.3V and 1.8V on the two side pins. This is part of step 6 in the "Start up operation" described in the technical manual, however I am not 100% sure if that implies that the TV got to step 6.
- I never got pins 13-15 on P6 to show 15v, i.e. the correct value according to the manual.

What is your opinion, based on the available information?
Could it be that the problem is actually the PSU and not the A board?

The A board for this TV seems really hard to find (or more expensive than getting a new TV), so I am hoping there's another way to fix this

[tvtimmy]

Re: Panasonic P50ST50B plasma TV: 13 blinks

A board is bad.

[faenil]

Re: Panasonic P50ST50B plasma TV: 13 blinks

well...yeah, that's what the blink code reports ^^

I find a bit strange that pins 13-15 are stuck at 2.15v, is that normal? Could it not be that the issue is actually in the PSU?

Is there anything else I can try, given that a replacement board is nowhere to be found?

[Biruslapio]

Re: Panasonic P50ST50B plasma TV: 13 blinks

I've had one panasonic P50V20 fail the 15V on the power board, it would not power on and I don't exactly remember the blink code, but I could turn it "on" by isolating the A and P board only, there was 3V at the gate of the 15V mosfet and that was enough to fool the 15V line detector, then it would be a green led but no sound and no image of course, VS was at 0V too. Remove the flat cables that goes to SC, SS and C boards, VSUS to SC and SS and leave only the main board, front led and psu connected.

Please list the complete pinout + your measurements of the PSU to mainboard connectors. Do you have VSUS even if for a brief moment?

[faenil]

Re: Panasonic P50ST50B plasma TV: 13 blinks

I've had one panasonic P50V20 fail the 15V on the power board, it would not power on and I don't exactly remember the blink code, but I could turn it "on" by isolating the A and P board only, there was 3V at the gate of the 15V mosfet and that was enough to fool the 15V line detector, then it would be a green led but no sound and no image of course, VS was at 0V too. Remove the flat cables that goes to SC, SS and C boards, VSUS to SC and SS and leave only the main board, front led and psu connected.

Please list the complete pinout + your measurements of the PSU to mainboard connectors. Do you have VSUS even if for a brief moment?

I tried unplugging the other boards, I think it did not make a difference (I will be unable to test on the TV until next Wednesday.

No, I don't think I have ever seen the VSus high.

F15V seems to be fine, while P15V is stuck at 2.15v

I will convert the pin readings from my previous post in a bit, I think I wrote everything in the first post, it's just the pins I did not mention were 0v

[faenil]

Re: Panasonic P50ST50B plasma TV: 13 blinks

Here are the volt measurements in different scenarios


TV plugged to AC but forced off:
1 0v
2 0v
3 0v
4 0v
5 0v
6 4.5v
7 0v
8 0v
9 0v
10 0v
11 0v
12 0v
13 0v
14 0v
15 0v

- After pressing power button:
1 0v
2 0v
3 0v
4 0v
5 0v
6 4.5v
7 3.0v, fixed
8 0v
9 0v
10 15.8v
11 15.8v
12 0v
13 2.15v
14 0v
15 2.15v

- After 2-3 mins, i.e. once the TV goes into shutdown and starts blinking red 13 times:
Not sure about this one (multimeter isn't working at the moment)
I think it was
1 0v
2 0v
3 0v
4 0v
5 0v
6 4.5v
7 0v
8 0v
9 0v
10 15.8v
11 15.8v
12 0v
13 0v
14 0v
15 0v

I also tested that the pin corresponding to the remote control power ON command shows 0.7v-0.8v when the remote power on button is pressed

[Biruslapio]

Re: Panasonic P50ST50B plasma TV: 13 blinks

Ok, it's missing the pins labels, 2.15V at P15V is too low, that is enough to not trip the 2 blink error code apparently, but test with only A and P boards connected, 15V is routed to SC boards via the flat cable.

Service manual pins read as:

1 Panel_Main_On
2 S1
3 S0
4 SOS4_PS
5 STB5V_ON
6 STB5V
7 F_STB_ON
8 GND
9 GND
10 F_STBY
11 F_STBY
12 GND
13 15Vc
14 GND
15 15Vs

The picture included says that P-Board is at fault if 15V does not appear even for a brief moment.

You need to have a reliable multimeter with proper batteries, all your voltage readings may be wrong and be misleading.

[faenil]

Re: Panasonic P50ST50B plasma TV: 13 blinks

Ok, it's missing the pins labels, 2.15V at P15V is too low, that is enough to not trip the 2 blink error code apparently, but test with only A and P boards connected, 15V is routed to SC boards via the flat cable.

Service manual pins read as:

1 Panel_Main_On
2 S1
3 S0
4 SOS4_PS
5 STB5V_ON
6 STB5V
7 F_STB_ON
8 GND
9 GND
10 F_STBY
11 F_STBY
12 GND
13 15Vc
14 GND
15 15Vs

The picture included says that P-Board is at fault if 15V does not appear even for a brief moment.

You need to have a reliable multimeter with proper batteries, all your voltage readings may be wrong and be misleading.

Oh sorry, you needed the pin layout...
Thanks for posting it.
I will be back on Wednesday and test the TV with only A and P connected.

Meanwhile I might be able to order a P board so I can have it by time I am back and I can test it

It was my fair that the P board could be at fault... Or, well, I was hoping it would be P more than A.

I will keep you posted, thanks for your help!

Feel free to provide any other pointer you may have

[tvtimmy]

Re: Panasonic P50ST50B plasma TV: 13 blinks

Don't waste your money on a power supply, it's a bad main icu chip on the mainboard.
I had the same problem on one of the US versions of this tv. There may still be re-balling services out there.

[faenil]

Re: Panasonic P50ST50B plasma TV: 13 blinks

Don't waste your money on a power supply, it's a bad main icu chip on the mainboard.
I had the same problem on one of the US versions of this tv. There may still be re-balling services out there.

I see, thanks for your input.
Is there anything I can do to make absolutely sure it's not an issue with the psu? (provided I cannot test it in another tv)

[Biruslapio]

Re: Panasonic P50ST50B plasma TV: 13 blinks

tvtimmy knows better, I wasn't suggesting an exchange of power boards, but troubleshooting to see what could it be, I have no experience on this model.

[tvtimmy]

Re: Panasonic P50ST50B plasma TV: 13 blinks

They start with the erratic turn on, then go to the freezing of the Panasonic logo, and then nothing at all. I got lucky and found a mainboard in New York. I found it on the ALL OF CRAIGSLIST page on the web.

[faenil]

Re: Panasonic P50ST50B plasma TV: 13 blinks

I see, so you think I should just go for a new A board (or look for a reballing service).

Unfortunately I cannot find any online for this model...
Do you know if I can use any TNPH0989 to get it going? Will the board for p50st50C work (I think that's the asian model)?

[faenil]

Re: Panasonic P50ST50B plasma TV: 13 blinks

Anybody knows if I can use a P50ST50C board on P50ST50B?

Any idea?