SAMSUNG PS42D51SX bad picture

[tom66]

Re: SAMSUNG PS42D51SX bad picture

See the jumper on CN200x (can't quite read it from here)

What happens if you move than one space across so it jumpers 3/4, I expect to see test patterns.

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

nothing changes no test signal

[tom66]

Re: SAMSUNG PS42D51SX bad picture

OK, we need to trace where XS and XG comes from.

They are both generated on the control board.

Do you see the resistor arrays like this:
http://www.lyhen.com/img/129809421519090000.jpg

Can you find XS on one of them and see if XG is nearby (likely same order as on the connector on the X-main.)

Also try reversing the cable to eliminate that possibility.

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

yes I see the resistor .XS passes through it. and goes to a small procesor

XG also passes through this resistor and goes to same procesor

BUT!!!!!
resistor on XS is 47 om
resistor on XG is 1.7k

[tom66]

Re: SAMSUNG PS42D51SX bad picture

"resistor on XG is 1.7k"

So, it is burnt out. You found the fault, the question is, is there a problem causing it to fail, or is it failed from wear and tear or whatever killed the Y-main in the first place. For now, I'd say jumpering across a 47 ohm resistor should be fine. You could possibly run a wire, with resistor, to the X-main, if it isn't too long.

What was the cause of the original fault?

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

"

What was the cause of the original fault?

I do not understand your question

[tom66]

Re: SAMSUNG PS42D51SX bad picture

"After damage to my TV, I changed this board which was quite damaged"

I interpreted this as some kind of damage was done to the TV like a power surge, is this not correct?

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

I have a little princess. She pressed the ON/OF button quickly two or three times .
I think this caused the problem with the first board "Y"

[tom66]

Re: SAMSUNG PS42D51SX bad picture

I have a little princess. She pressed the ON/OF button quickly two or three times .
I think this caused the problem with the first board "Y"

I'd say that's unlikely. It could have done it, but more than likely the board wore out, which is common with Samsungs, the transistors run far too hot.

I'd try fixing that high resistance then see if you can get a good picture.

This is the first time I've ever seen a signal go missing from a control board. I'm pretty surprised, but I suppose anything can happen!

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

when i change the resistor, will write

Thank you again for your time : P:

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

Tom Add one more to the plasma TV saved from trash
Many many many thanks for the help you gave me

I hope to have more people like you

Best Regards

[kevinm34232]

Re: SAMSUNG PS42D51SX bad picture

Wow, that was pretty cool Tom..

I have a question, which resistor was bad and how did you know the values?

Also what was the exact fix to the problem, did you replace the SMD resistor?

[tom66]

Re: SAMSUNG PS42D51SX bad picture

The bad resistor was on the control board, I believe. These resistors can be damaged by flex and shock. It is possible when the TV was removed from the stand for service that it got cracked. But that seems like a really bad coincidence!

The symptoms were consistent with an X-main failure and so many times simply replacing it has sorted it, well, it's not always that easy!

The only way we found it was by noticing the X-main output was too high, it was never being pulled low (floating around 100V), which to me indicated a fault somewhere with the XG fet. (Samsung give all switches on their X-main two-character name. XS=Sustain Supply, XG=Sustain Ground, XF=Forward ER, XR=Reverse ER, XE=Voltage Ve Bias, plus a few others I can't remember.)

Scoping the XS showed missing signal, so the natural question was where the signal was going missing, and it turns out, that those resistors can fail, with no apparent cause!

Anyway, enjoy the TV! You now have two spare X-main boards?

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

I cut path and put a new resistor here, damaged resistor -it bypassed

[tom66]

Re: SAMSUNG PS42D51SX bad picture

Ah, so it had failed on X-main??
But you replaced that board twice!

Did both other boards fail too?

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

No No my friend the X -bord is perfect ,There was simply more space for the X bord to installation of new resistor.

Bad resistor on the other board but there is no place to bi instal new resistor

[tom66]

Re: SAMSUNG PS42D51SX bad picture

OK, I suppose, you just put jumper on control board?

[Stanislav]

Re: SAMSUNG PS42D51SX bad picture

OK, I suppose, you just put jumper on control board?

Yes Tom
thanks again

[kevinm34232]

Re: SAMSUNG PS42D51SX bad picture

Is that a through hole resistor you used, I cant see it? What value is it and how did you know what the values should be of those resistors?