Help identify boards in Samsung plasma

[Alastair E]

Re: Help identify boards in Samsung plasma

Thing is--even if you did that the PSU would still shut down because the control-board cannot 'see' the correct waveform from that board.

The fact that the supply rises then falls on turn-on suggests there's no dead-shorts on either board.
More likely there's a fet etc thats gone open or an on-board derived supply (Y-SUS) is absent....

[jaxmc1023]

Re: Help identify boards in Samsung plasma

"control board" meaning Logic board or the main board with inputs?

[tom66]

Re: Help identify boards in Samsung plasma

Logic board.

[jaxmc1023]

Re: Help identify boards in Samsung plasma

I'm pretty confused now.. Everything I'm reading is telling me that Part# BN96-22107A is referred to as a "X/Y Main Board" or "X/Y Sustain"..

The power connection to the Sustain board has 13 pins -- Pins 5 thru 10 are all marked "X-Out"

[tom66]

Re: Help identify boards in Samsung plasma

I can understand your confusion. I think the X/Y main has some functionality of the X-main integrated on it. The X-buffer has what little remains on it. It is an odd design, though. I've never seen it done before.

[jaxmc1023]

Re: Help identify boards in Samsung plasma

What would be your next move? I can't find any shorts on the Y-Buffer (the old one or the new one).. Stand-by and PS_On voltages are correct. VS and VA voltages are correct for a brief moment, but drop out as soon as screen flickers white noise for a split second.

If I put the old Y-Sustain board back in, would there be any reason that it would damage the new Y-Buffer? or is it always the other way around -- Bad buffer blows Y-Sustain.

[jaxmc1023]

Re: Help identify boards in Samsung plasma

I put the old X/Y Main board back in with the replacement Y-Buffer. Unit turns on, startup jingle, NO PICTURE CHANGE, and voltage drops out

Took the old back out.. put in the replacement X/Y Main. Unit turns on, startup jingle, brief split-second flash of white noise, and then voltage drops out

Is this useful info?

[jaxmc1023]

Re: Help identify boards in Samsung plasma

Vs on power supply is 209v (right on the money)
Va is only 50v - supposed to be 58v

Vsc on X/Y Main is -184v which is perfect, and it actually holds for a few seconds before shutting down

According to the fast track, the VA travels through the x-buffer, then through the logic buffer on the bottom of the panel, before reaching the logic board

I don't think the y-main is at fault because it generates the correct Vsc before shutting down.

Can a Va that's too low signal the logic board to shut off the power supply?

[Alastair E]

Re: Help identify boards in Samsung plasma

The VSc inverter on the Y-SUS in your case, seems OK--However, the Y-SUS board has a LOT more stuff than the VSc inverter on there....

A Low Va could I guess signal a shut-down, although how low this threshold is--Ive no idea....
Excessive Va will also shut the set down, as excessive Va can destroy the COF chips on the panel tabs....

Think at this stage, I would set the PSU to run on its own by grounding VS-ON by 1K and applying 5V via 1K to PS-ON.
--Then check the Va and Vs, set accurately and try again.

[jaxmc1023]

Re: Help identify boards in Samsung plasma

There is a VE voltage listed on the panel sticker, but I can't seem to figure out which Test Point I should test at

The only one that looks similar to the VSC test point is marked "VE JP"

[Alastair E]

Re: Help identify boards in Samsung plasma

Aye--Thats prolly it.....

[jaxmc1023]

Re: Help identify boards in Samsung plasma

Do you think it matters which of those two wires at "VE JP" i test across?

[Alastair E]

Re: Help identify boards in Samsung plasma

I'd check on one nearest arrow....

[jaxmc1023]

Re: Help identify boards in Samsung plasma

OK. I won't be able to mess with it until I get back home.

Assuming the VE does the same as the Vsc (rises to normal level before falling off to 0), is there any danger in trying to increase the Va up to its expected level of 58v?

I turned the pot at Va last night about 1/8 of a turn, and that increased it maybe 1v. Was afraid to go much further than that

[tom66]

Re: Help identify boards in Samsung plasma

I had an LG plasma PSU that would shut down with a Va of less than 57V; sticker was 60V.

[jaxmc1023]

Re: Help identify boards in Samsung plasma

I had an LG plasma PSU that would shut down with a Va of less than 57V; sticker was 60V.

You think it's risky to turn that pot enough to go up 8 volts? IF that were the root cause, that would pretty much point to a faulty power supply, wouldn't it?

[tom66]

Re: Help identify boards in Samsung plasma

I'd try increasing Va to the sticker rating but nothing more; the risk is with high Va, the plasma panel can be irreparably damaged.

[jaxmc1023]

Re: Help identify boards in Samsung plasma

I turned the Va adjustment Pot as far as it would go, which was only about a half turn. The Va barely reached 51v.

I found the Ve test point, and it reads 102v -- sticker says it should be 91v

Tried adjusting Pots for Ve and Va, but can't turn either of them enough to move them more than 1-2 volts..

[jaxmc1023]

Re: Help identify boards in Samsung plasma

I've got another power supply coming in.. Was supposed to be delivered today. Looks like it's going to be late, of course.

I'm out of ideas otherwise. I can't find any shorts on X/Y Main, Y-Buffer, or anywhere else. All voltages do exactly what they're supposed to do, except Va is short by 10volts. Then they all just drop out

[jaxmc1023]

Re: Help identify boards in Samsung plasma

Replaced power supply -- all voltages exactly the same. Va still showing 50v when panel is calling for 58v.

I've checked all over the X/Y Main and Y-Buffer, and can't find a short anywhere.

The only other thing that I'm noticing that seems strange, is the voltages for the IR sensor/switch are a little off -- at least according to the fasttrack. Standby voltage is correct at 3.3v, but the guide says all other voltages should be 3.3v also. None of the other voltages - key 1 or key 2 -- is higher than 2.0v.

Was finally able to get a picture of what the screen does when i turn it on -- flashes this for less than a second.