PN50A400C2DXZA partial picture.

[Mad_Professor]

Samsung PN50A400C2DXZA
I got a TV in for repair today, Seems to be the right side of the screen has black bars running down it and to the far right just seems to be black

Left side seems to be working. I did the test pattern and it does the same thing.

I'm not sure if it's the Main Logic, or if it's right logic buffer.
I don't want to throw parts at it if the panel is shot.

Also on the Main Logic board, LED 2 is flashing continuously.

[tom66]

Re: PN50A400C2DXZA partial picture.

Loose connector, bad C board, bad control board or fair chance of plasma panel being bad.

[Mad_Professor]

Re: PN50A400C2DXZA partial picture.

Loose connector, bad C board, bad control board or fair chance of plasma panel being bad.

Verified that connectors were not loose, What's a C Board? is that Main Logic or Input?

[tom66]

Re: PN50A400C2DXZA partial picture.

C board = board at bottom of plasma panel (E&F buffer) which connects to Control/Logic.

[Mad_Professor]

Re: PN50A400C2DXZA partial picture.

The C Board can't be replaced? right?

[tom66]

Re: PN50A400C2DXZA partial picture.

Not always replaceable on Samsung panels.

[Mad_Professor]

Re: PN50A400C2DXZA partial picture.

Well I replaced the main logic, but no go, same problem. So I tore down the tv and gain access to E buffer board.

Now I noticed it's just caps and resistors, no IC, diodes or transistors.
I was taking capacitance measurements then compared it to the F buffer board, and noticed I was getting low values on E buffer compared to the F Buffer 1.2μF on the 20μF of my meter.

I tested all of them, these are the ones on E buffer that didn't compare to F buffer.

All done on 20μF setting
C2537 = 0.48
C2536 = 0.50
C2528 = 0.50
C2517 = 0.47
C2516 = 0.35
C2515 = 0.36
C2514 = 0.35
C2513 = 0.12
C2501 = 0.11

While on the F buffer board in the same sequence all of them tested 1.2μF.

Question is can MLCC lose capacitance? Is the problem 2501 and 2513 or everything up to C2516 is bad?

[tom66]

Re: PN50A400C2DXZA partial picture.

No, MLCC cannot lose capacitance. They are pretty solid state. They tend to work or not.

I suspect one of those bonded chips on the panel ribbons has failed, non replaceable. It's dragging down the signals for others.

Looking at this, I can't see any heatsink for those?! Am I missing something? If that is the case, that is crazy, no wonder they fail so quick!

[Mad_Professor]

Re: PN50A400C2DXZA partial picture.

No, MLCC cannot lose capacitance. They are pretty solid state. They tend to work or not.

I suspect one of those bonded chips on the panel ribbons has failed, non replaceable. It's dragging down the signals for others.

Looking at this, I can't see any heatsink for those?! Am I missing something? If that is the case, that is crazy, no wonder they fail so quick!

Bonded chips? I don't see any chips on the ribbons. Are they deep in the panel?

From what you're telling me, replacing these MLCC would be futile because the actual panel is bad?

Heatsinks!? where? on the ribbon or the boards themselves? I did have a strip of metal that was the width of the TV that goes on top of boards.

[freakaftr8]

Re: PN50A400C2DXZA partial picture.

The ribbons that are on the bottom of the panel. you can't see them because the metal strip underneath the ribbons is the actual heatsink against the chips Embedded in the ribbon cables.

you will see two or three sets aboard going across the bottom of the panel these boards Are C boards. one or more of those chips have Failed non replaceable

[Mad_Professor]

Re: PN50A400C2DXZA partial picture.

The ribbons that are on the bottom of the panel. you can't see them because the metal strip underneath the ribbons is the actual heatsink against the chips Embedded in the ribbon cables.

you will see two or three sets aboard going across the bottom of the panel these boards Are C boards. one or more of those chips have Failed non replaceable

Those are the C boards in the photos they are labelled E & F buffers. But I do see what you mean, I've lift the E board up and saw white thermal paste on each ribbon, so I guess that where the bonded chips are.

So PANEL is FUBAR.

[freakaftr8]

Re: PN50A400C2DXZA partial picture.

well possibly you could try disconnecting the ribbon cable associated with the black line one by one and then Power up to see which one is loading down the other side of the screen if the one you lift up brings back the rest of the picture then you know the panel is bad