Panasonic Plasma TH-42PV80, 7 blinks

[octaver11]

So, I bought this TV at scrap value, with everything intact, boards and all. Previous owner said the TV was working and suddenly display became grainy/hazy, incorrect colors (magenta, pink, etc.) including the menu. He brought the TV to a local TV repair shop but was being charged USD500. So he just decided to sell it as scrap.

At first when I powered up the TV, I got 7 blinks. Referring to the service manual which I downloaded from the internet, I tried isolating SU/SD boards to check if SC is defective.

I disconnected SCs 41,42 and 46 and jumper wired HV screw to L801. The TV powered, LED turned green, no error blinks, panel lights (Pic1).

However, I smell something burning and found it to be coming from SD board's IC654 (AN16082A, Pic2, third chip from the bottom) and when I checked, it had burnt holes on top of it. Removed SD board from the TV and probed the connector for shorts in a zipper manner. Found shorts on that particular IC.

If I power up the TV without the SD board (disconnected from the panel), I get top half of the panel lighting up. I can also let it light up for more than 10 seconds which is not possible for me to do if SD is connected to the panel (burning IC654).

My questions are,
Is my panel shorted in the lower half where the IC burns?
Is it just a bad SD board where it is safe to just replace it and make it work?
Does the SC board have something to do with the SD board chip failing?
Can I disconnect panel ribbon where the defective chip is and safely power on the TV?

These are the Part Numbers:
SD TNPA4400
SC TNPA4644
SU TNPA4439

Appreciate your inputs.

[tom66]

Re: Panasonic Plasma TH-42PV80, 7 blinks

I do love these sets; well built. Kept two myself! Find it hard to part with them; such a great image quality and only a few minor problems, but usually easily fixed.

A little research suggests PV80 is a FHD set based on PZ80 with a few specifics for SE Asia. Possibly cost cut like UK PZ8B or American PE80U (which, despite model # being same as the old 480 line E-series Panasonics, is a FHD model.) How many HDMIs does this set have? Does it have PC VGA? What about SD picture viewer?

The PZ70s have tons of issues with panels going short killing buffers. At least 20 to 30% of 7 blinks has to be bad panel.

While it CAN happen with PZ80 series (2008 FHD PDP in 42"), the problem is greatly reduced. Usually, on both types of panels by looking carefully for obviously burnt pixels with a torch, and the panel switched off.

PZ70 in 42" was a massive achievement in 2007, no one had made a 42" or 50" Full HD 1080p plasma back then. I believe LG came out with a 50" in 2008 and Samsung 50" in 2009. But no one has ever hit 1080p at 42" apart from Panasonic... Needless to say, it was a massive achievement but the very high pixel density (for a plasma; it makes LCD or AMOLED look really dense!) meant any dirt/contamination occurring during manufacture could lead to a pixel failing shorted blowing the buffer within short order -- usually the TV would work about 30 seconds to 10 minutes with the short, before the buffer chip hits thermal runaway and smoke comes out.

PZ80 (2008) is a highly refined variant of PZ70 (2007), a lot less cost to make and a lot more reliable, picture quality better too and power usage a little lower. It's a single scan design instead of dual scan, lowering the panel manufacture cost.

Anyway, away from those asides...

Yes, you can power TV on with buffer ribbons removed with no harm done.

However, please note, the 6 blinks ERC "MID" volt sense -may- detect a fault if too many ribbons are out. Not an actual malfunction, you see, just dropping the MID voltage below a threshold point. (This will also cause LED on SC to go dim or out.)

SC provides -Vad and Vscn voltage. The Vscn is imposed on -Vad. From memory, -Vad is -130V, Vscn is 170V, which puts the Vscn to ground measurement at about 40V above ground.

The buffer board only EVER sees Vscn on these. Its job is to switch between the VFG (floating ground) which is the sustain board's job (SC board) and the VFG+VSCN. So the highest voltage it sees is about VSCN plus/minus some transients.

VSCN too high or low will trigger 7 blink as will VAD being too high or low.

D board failure can also cause 7 blinks, but that's very rare.

Just something to look out for so it won't throw you off. I'm sure tw2005 the resident Panasonic guru will have some more info to supply.

[octaver11]

Re: Panasonic Plasma TH-42PV80, 7 blinks

Thanks tom66 for your inputs.

Indeed, the 42PV80 is a well-built HDTV in its era, 2008. Actually, its is an HD G11 Panel (MC106H30T11A) released exclusively for South East Asia and I feel lucky to have one which up to this date is flawlessly working. I think the equivalent model in the UK or US is the 42PX80 which has almost the same boards except for the A-board. Mine has 3 HDMI inputs, VGA, composite, component and S-video, SD card reader and a very good AR filter. It had this rising black level but I was able to restore by tinkering the EEPROM using an Arduino programmer (found in this link http://panasonic.mironto.sk/).

Anyway, back to the problematic TV,I disconnected the panel ribbon wire as shown and I still get the burning smell of IC654 (AN16082A) which led me to conclude that there are no shorts in that specific area of the panel. The panel lighted up but with a black horizontal stripe in the area where the ribbon was disconnected, which I think should be the case. Notice how IC654 is about to pop out like an acne pimple?

Is that chip getting power somewhere even with SC42 disconnected? The SD board is basically isolated from the SC board and the only way it is physically connected to the SC is via the HV.

I’ve been contemplating on getting the SD board from my working unit to test it in this TV, but something tells me that this is a bad idea

I would love to hear from tw2005, wish he could find time to give some inputs.

[tom66]

Re: Panasonic Plasma TH-42PV80, 7 blinks

Ah, yes. It's 720p; I found one result suggesting 1080p but I guess that's wrong. Our close model would have to be a PX80 (still a very nice TV!)

What you can try doing is lifting that chip off. Sometimes, this will allow part of the panel to work, but it will cut off around that bar (the drive signals for the panel are chained.)

You will probably find if you measure Vscn it is measuring low. On some of these sets -Vad circuit generates Vscn too so a low Vscn would cause low -Vad. Check service manual (see my signature) for Vscn and -Vad set points.

[tw2005]

Re: Panasonic Plasma TH-42PV80, 7 blinks

I'd say a bad buffer dragging the display down especially if that buffer IC is burnt or bulging. I'm little reluctant with these older models due to lack of experience with them and wary because of the possibility of a bad panel taking the SD out.

Now that you have shown us the SD, I think the only way forward would be replacing it.

If the SD is not too expensive and easily obtainable and you have one on hand I don't see the difference between trying your other board or buying one to try.

Either you'll solve it or blow it in which case you would have to had purchased one to try anyway. Just you'll be without the other TV until you get another board.

I am a little surprised with Pic1 seeing such a bright display with the SD/Su disconnected and the bands still in the bottom.

Sorry but not 100% sure with what I see.

[octaver11]

Re: Panasonic Plasma TH-42PV80, 7 blinks

hi tom66. I'll try removing the chip first as per your suggestion and see how it goes.

hi tw2005, thanks for your advice. It seems the logical way to deal with the buffer board. I decided not to mess up with the working TV anymore and just purchase the board somewhere.

Many thanks to both of you guys for your unselfish advice in helping those in need of your expertise. I'll keep you posted.