Panasonic Plasma TV LED blinking 12 times

[PaulF]

My Panasonic TH-50PX70B TV has developed a fault indicated by the red LED blinking 12 times. I have searched the internet and the blinking LED fault codes seem to differ between models. From some comments on this forum I think it is most probably the power board.
If a can be sure it is this board I would be happy to replace it. it would be even better if I could repair it.
Does anyone have any more info on this model or can give me some pointers on tests to identify where the problem is.

[tom66]

Re: Panasonic Plasma TV LED blinking 12 times

12 blinks is sound SOS. From PX75 manual, a similar TV:


This can be:
- bad/damaged speaker (shorted)
- wiring shorted together, or to frame
- A board fault

[PaulF]

Re: Panasonic Plasma TV LED blinking 12 times

Thanks for the info Tom66.
Good job I asked, thought it was the power board.
I'll investigate and post my findings.

Much appreciated.

[PaulF]

Re: Panasonic Plasma TV LED blinking 12 times

Following checks on the speakers & wiring I have ordered a replacement 'A' board.
Are there any adjustments required following fitting of this board? i have most basic test equipment eg. multimeters, oscilloscope etc.

[EIEIO]

Re: Panasonic Plasma TV LED blinking 12 times

Hello Badcaps Forum. I found this board looking for an answer to my "12 Blink" issue on a Panasonic TC-P42S1 plasma. I've read about everything on here and other websites trying to determine if I can fix it for about $200 or so. If not, I'll probably buy new.

The TV is about 3-4 years old and has had no issues until one day on power down, we heard an additional click after it shut off and immediately the SOS light started flashing.

Here's what I've checked:
- unplugged SC board, 12 blinks
- unplugged SS board, 12 blinks
- unplugged both SC & SS board, 12 blinks
- Checked standby and power on voltages coming into A board and all are correct
- no shorts in speaker wiring or speakers
- connected speaker to alternate signal source and the speakers function properly.

By all I've read here and from other sources, it's the A board. However, my A board (TNPH07861A) isn't available many places other than used ones on Ebay with prices from $120-212.

My questions:

1. How critical is the board version? I have found TNPH0786AF at ShopJimmy & TNPH07862A versions. (I'm assuming they wouldn't work or can't be changed)
2. Is there a way to bypass the sound amplifier altogether and just use a sound bar?
3. Has anyone used ModusLink PTS (http://www.moduslinkptstvboards.com/txn-a1efuus/) for board repair? (This is the direction I'm leaning)
4. Is there anything else I should do/check before reinstalling a replacement A board?

Any other suggestions would be appreciated. Thank you in advance!!

[tw2005]

Re: Panasonic Plasma TV LED blinking 12 times

Hello Badcaps Forum. I found this board looking for an answer to my "12 Blink" issue on a Panasonic TC-P42S1 plasma. I've read about everything on here and other websites trying to determine if I can fix it for about $200 or so. If not, I'll probably buy new.

The TV is about 3-4 years old and has had no issues until one day on power down, we heard an additional click after it shut off and immediately the SOS light started flashing.

Here's what I've checked:
- unplugged SC board, 12 blinks
- unplugged SS board, 12 blinks
- unplugged both SC & SS board, 12 blinks
- Checked standby and power on voltages coming into A board and all are correct
- no shorts in speaker wiring or speakers
- connected speaker to alternate signal source and the speakers function properly.

By all I've read here and from other sources, it's the A board. However, my A board (TNPH07861A) isn't available many places other than used ones on Ebay with prices from $120-212.

My questions:

1. How critical is the board version? I have found TNPH0786AF at ShopJimmy & TNPH07862A versions. (I'm assuming they wouldn't work or can't be changed)
2. Is there a way to bypass the sound amplifier altogether and just use a sound bar?
3. Has anyone used ModusLink PTS (http://www.moduslinkptstvboards.com/txn-a1efuus/) for board repair? (This is the direction I'm leaning)
4. Is there anything else I should do/check before reinstalling a replacement A board?

Any other suggestions would be appreciated. Thank you in advance!!

Little curious about the part number you've quoted TNPH07861A, sounds like the PCB print number.

What other numbers can you find stamped on the board or a white sticker but not the one on the tuner module?

A few have had SC boards repaired/refurbed at moduslink, can't remember reading any bad reports.

[tw2005]

Re: Panasonic Plasma TV LED blinking 12 times

I'd stick to

TXN/A1EFUUS or TNPH0786 no suffix. There's a matrix on the PCB above the TNPH0786 number. The suffix is determined by the placement of 5 jumpers above that table which you decode looking at the dots labelled in the matrix.

SJ says yours has no suffix which I suspect means there'll be no jumpers.

The AF is a 46" panel.
42U1, version AE I suspect would work however A30 is missing for the fans.
So it should work as they have the same panel, you won't have fans running.

That's what I see at a glance.

[EIEIO]

Re: Panasonic Plasma TV LED blinking 12 times

TW2005,

You are correct that the part number is TXN/A1EFUUS and the board number is TNPH07861A. There is no suffix that I can tell. Pictures are attached of the board numbers I find and the panel info.

[PaulF]

Re: Panasonic Plasma TV LED blinking 12 times

I've just replaced the A board (2 boards to be exact TNPA4177 and TNPA4226) and the problem is still the same, ie 12 blinks. Any ideas where the problem can be now?

[tw2005]

Re: Panasonic Plasma TV LED blinking 12 times

I've just replaced the A board (2 boards to be exact TNPA4177 and TNPA4226) and the problem is still the same, ie 12 blinks. Any ideas where the problem can be now?

So there is no A-board, but DG(TNPA4226), H (TNPA4177), D (TNPA4133), PA(TNPA4178).

Maybe download the service manual

See if you can check +15V_S is going to the H board at H3 pins 21-23, delivered from PSU P6 pins 2-4 via PA board, in PA6, out PA3 , in H3

H board IC2301 needs Sound15V, Sound12V. Sound12V is generated from the Sound15V(+15V_S) by the voltage regulator IC2303.

It appears IC2301 generates the SOS, and a high is operate, a low is SOS so i guess if there was no 15V that would mean a low from that and trip the SOS12.

I've got no experience with this generation so I'm just going by the schematic since there's no mention of any voltage checks.

It may be the case that you will have to hook up the probes first and then power on to detect the 15V because I expect SOS12 will kill the 15V when tripped.

There was another post for similar problem with no result unfortunately.

https://www.badcaps.net/forum/showth...hlight=50PX70B

Manual shows P or H board as first checkpoints in the blink chart.

[PaulF]

Re: Panasonic Plasma TV LED blinking 12 times

Thanks for the reply, yes you are absolutely right about the boards. I'll do the checks you suggested and hope I can trace the board where the fault is. Thanks for the link to the manual, it's a great help, was trying to use a manual for a similar set but had an A board instead of the H & DG boards which is why I replaced them both.
If it's the P board I can get a replacement but want to be sure before I go ahead, looks like I've already replaced 2 unnecessarily.
Thanks again for taking the trouble to help.

[PaulF]

Re: Panasonic Plasma TV LED blinking 12 times

I've done the tests as you suggested and at H3 pins 21-23 & P6 pins 2-4 the voltage only rises to 1.56v max before it is tripped off. Looks like it could be the +15v from the P board? I assume this voltaage is reference to the chassis ground?

[PaulF]

Re: Panasonic Plasma TV LED blinking 12 times

Further tests show that I have 15v at TP7 which is upstream of Q351 FET which appears to switch the 15v to P6 pins 1-4. I plan to investigate further at the weekend when I can borrow a probe from work which is small enough to get onto the gate to see if the gate drive is ok.
I have not yet been able to identify the FET from it's number NEC 25K2510.

[tom66]

Re: Panasonic Plasma TV LED blinking 12 times

Try 2SK2510.

[tw2005]

Re: Panasonic Plasma TV LED blinking 12 times

I've done the tests as you suggested and at H3 pins 21-23 & P6 pins 2-4 the voltage only rises to 1.56v max before it is tripped off. Looks like it could be the +15v from the P board? I assume this voltaage is reference to the chassis ground?

Maybe, how long after the 1.56 does it shutdown? Is it a steady 1.56 or rising when it kills.

The other thing I'm looking at is Q2301 and test point TP2301, I suspect gose high on the SOS.

I guess what we really need is either to figure a way to test the voltages from the PSU as if the TV was running or I'm thinking if TP2301 if it's high on the trip, earthing that out and see if the TV powers up with no blinks.

Then recheck the voltage.

There's probably a more correct way, is there anything in the other post that helps.

Both H boards are doing the same assuming both are good suggesting the problem is elsewhere.

I don't want to say it's the PSU unless it's proven the 15V_S can't be generated.

[tw2005]

Re: Panasonic Plasma TV LED blinking 12 times

I was wonder looking at the diagrams, looks like this PSU has those modules (MC351)similar to that in the 46PZ800 and others which had 2 & 10 blink issues generally due to a bad ceramic cap on the module?

I believe they were loss of 15V related too.

Edit: but then you did say you have 15V, keep digging, hope you find the culprit.

[tom66]

Re: Panasonic Plasma TV LED blinking 12 times

(error on my part, please ignore)

[tw2005]

Re: Panasonic Plasma TV LED blinking 12 times

[tw2005]

Re: Panasonic Plasma TV LED blinking 12 times

Further tests show that I have 15v at TP7 which is upstream of Q351 FET which appears to switch the 15v to P6 pins 1-4. I plan to investigate further at the weekend when I can borrow a probe from work which is small enough to get onto the gate to see if the gate drive is ok.
I have not yet been able to identify the FET from it's number NEC 25K2510.

Don't forget you have the SM. As per Tom's response. Q351 search in the PDF gives you 2SK2510.

There's actually a lot of true part numbers in there unlike the later manuals where they get Panasonic coded numbers which are meaningless most of the time.

[PaulF]

Re: Panasonic Plasma TV LED blinking 12 times

The voltage increases gradually over a couple of seconds and reaches a max of 1.56v which is steady for probably about a second then shuts off. Will do the test again and take better note of what happens. tw2005 I agree with what you are saying, I'll check out Q2301.
I did identify the FET as 25K2510, I just can't seem to find a data sheet for it to see it's spec in case it is faulty and need to find an equivalent.
Thanks for the help guys.