Samsung Plasma (PN58C8000) won't power up.

[tee el cee]

After I posted, I found an excellent troubleshooting doc here.

http://www.toms-service-manuals.com/...h=Submit+Query

Vs, Vs, Ve, and Vsc are all there briefly before the power supply shuts off. I didn't realize you had to measure right at power-on. I'll check the other points and re-post tomorrow.

[tee el cee]

Re: Samsung Plasma (PN58C8000) won't power up.

I'm using the fast track guide here: http://www.toms-service-manuals.com/...h=Submit+Query
But I don't know if this is PS problem or LOGIC problem or ??

Details:

The TV went blank while we were watching it and has never come back.

Now, when I try to power it on after it's been unplugged for a bit, there's a 'chunk chunk' sound from the region of the power supply, the Standby LED blinks 4 times then stays off. The green LED on the LOGIC panel blinks slowly. The screen stays blank. I can't bring the TV menu up.

Subsequent off/on cycling does not make the standby LED blink.

Basically, the power supply shuts down immediately. Vs, Va, Ve, and Vsc (labeled Vscom?) all hit their targets briefly and then fall off. Neither Vs nor Va are shorted to ground.

The lines to the MAIN board
are marked: 18, 18, 5.3, 5.3, gnd, gnd, 15, 15, 15, ps. on, stdby, 5.3, gnd, gnd, gnd, gnd, n/c, n/c,
and read: 17.5, 17.5, 5.2, 5.2, -5.3, -5.3, 15, 15, 15, 126, 5.2, 5.2, (can't reach the rest)

The lines to the LOGIC board
are marked: 5.3, 5.3, gnd, gnd, PS_ON, VS_ON,
and read: 5.2, 5.2, -5.6, -5.7, 125, 1.0.

I tested all the fuses I could see and there are no visibly bulging caps.
This is the power supply http://www.shopjimmy.com/samsung-bn4...wer-supply.htm

So, which board is the problem and what's my next move?

Thanks!
TLC

[tvtimmy]

Re: Samsung Plasma (PN58C8000) won't power up.

Remove the connector from the mainboard to the logic control board and use a small "roach" clip to short pins 3 &4 on control board. If you see nice clear test screens the mainboard is bad.

[tee el cee]

Re: Samsung Plasma (PN58C8000) won't power up.

Remove the connector from the mainboard to the logic control board and use a small "roach" clip to short pins 3 &4 on control board. If you see nice clear test screens the mainboard is bad.

In this configuration, I got no LOGIC board LED, no chunks, and nothing on the screen. I measured standby and ps_on at 5.2 and 2.8.

I also tried this configuration AND shorting ps_on to ground using the MAIN side of the cable as suggested by the fast track linked above. I got the chunks, the slow flashing LOGIC board LED, and nothing on the screen. Standby and ps_on measured 5.2 and -3.2.

EDIT: Then I additionally disconnected the LVDS from LOGIC to MAIN. (Saw it on a youtube vid.) Same result.

Thank you.
TLC

[tee el cee]

Re: Samsung Plasma (PN58C8000) won't power up.

So does that mean we've cleared the MAIN board?

Any ideas, anyone?

[tee el cee]

Re: Samsung Plasma (PN58C8000) won't power up.

I think I found it. I pulled the power board to look at the back and it looks like one of the transformers (?) has been hot. If you zoom in, you can see that the plastic coating on the leads have been melted off on one side.

Then I flipped it back over and noticed that there are brown marks on nearby. At first I thought that the transformer had melted off a pretty "rim cover" (?) that the others had. But pics of new boards don't have that either.

I haven't any luck finding the part number (QGAH00231). I'd probably buy the board anyway. Does this look like my problem and match my other symptoms? I saw 125 volts on one of the pins earlier, which I think is a sign of a transformer short.

Anyone want to recommend a place to buy the board? Samsungparts.com has it for $200. It's on ebay for $83...

Thanks!
TLC

[tee el cee]

Re: Samsung Plasma (PN58C8000) won't power up.

Help, please!

I bought & tried a new power board and apparently that wasn't my problem.

Symptom summary:

• Black screen. Red Standby LED flashes on power up. Cannot trigger Menu.
• No power on "chime" is heard, but I had the speaker disabled because the TV was downstream of my AVR.
• Green, LOGIC board LED flashes slowly. About every 5 seconds.
• STBY 5V is OK.
• PS_ON transitions from 3.3v to ~124v (instead of 0v) with power on.
• Vs, Va, Ve, and Vsc all hit their targets briefly on power on then fade (fast track says this model shuts down PS on problems).
• "Roach clip" "logic board test patterns" cannot be seen.

From what I've read, the POWER board behavior when X-main and Y-main are disconnected is often used to decide where to look next. But according to the fast track, this model's POWER board shuts down when they're disconnected, too. So where do I look next?

Thanks,
TLC

[tvtimmy]

Re: Samsung Plasma (PN58C8000) won't power up.

Did you find the logic board test pins? On your pic there is a white arrow pointing to the pins. You get nothing from removing the ldvs cable and shorting out pins 3&4?

[tee el cee]

Re: Samsung Plasma (PN58C8000) won't power up.

Did you find the logic board test pins? On your pic there is a white arrow pointing to the pins. You get nothing from removing the ldvs cable and shorting out pins 3&4?

Black screen. Slow blinking LOGIC LED.

[tee el cee]

Re: Samsung Plasma (PN58C8000) won't power up.

A step forward!

Based on a tip here: https://www.badcaps.net/forum/showpo...9&postcount=61

I tried disconnecting the flat cables to X-Main and Y-main. When Y-Main is disconnected, the LED blinks fast instead of slow! I think this means I've narrowed it to the Y- boards. (Or the LOGIC board?)

Also, Vs, Va, Vsc, Ve are all good. VS_on is 3.2 and PS_ON is still high at 124v.

This tech bulletin describes checking for shorts around OUT_H and OUT_L. But I can't find my OUT_H and OUT_L. Can you?

Can anyone help me move forward?

[tee el cee]

Re: Samsung Plasma (PN58C8000) won't power up.

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