samsung plasmas & lightning

[zape]

Re: samsung plasmas & lightning

Ok here is what I did:

1) Shorted Pins 3-4 on the control board
2) Disconnected the LVDS cable from the main board
3) Disconnected the power cable from the main board.
4) Plugged into MAINS
5) Shorted the PS-ON to GND

The TV switched on for a second but then turned off.
I noticed some leds blinked on the control board and also panel flashed.
I was checking VS-ON while shorting the PS-ON and it would go up to 3.3v for a moment and then goes back to 0v.

It looks like VS-ON goes to zero and I have no way to check the Va and Vs voltages as suggested in the video.
Does it mean the control board is faulty? It that the one that should generate the VS-ON signal?

[heavymachines]

Re: samsung plasmas & lightning

Assuming it was done correctly, which it seems. Ctrl board is not likely at fault. Now it is time to disconnect y and x mains see if you can get power supply to stay on.

[zape]

Re: samsung plasmas & lightning

I disconnected the two boards as shown on the photo (highlighted in red).
No change. The PSU turns on and immediately shuts off.

[heavymachines]

Re: samsung plasmas & lightning

Congrats you narrowed down to fault. If ps still shuts down even forcibly and still no VS or VA voltages or just briefly.

[zape]

Re: samsung plasmas & lightning

So it is the PS, and not the control board?
VS_ON is generated by the PS itself, right?
I thought VS_ON is coming from the control board so the control board may be at fault. Should I try to jump the VS_ON signal somehow and see if PSU will turn on fine?

[heavymachines]

Re: samsung plasmas & lightning

Plasma power supplies generate the VA and VS voltages. Jumping ps_on will force ps on, plasma power supplies can be turned on without anything connected to it with just ps_on jumped and A/C from wall connected. The control board just drives images to panel. i suppose if for a very rare reason if shorted it could cause power supply to shut down if detected a short but unlikely you can retest with just the ps and nothing else connected but just a/c from wall and ps on jumped.

[heavymachines]

Re: samsung plasmas & lightning

That has been my experiences with plasma tvs, Now i suppose a more experienced person like tom66 and others can put their thoughts on this for a second opinion.

[zape]

Re: samsung plasmas & lightning

I disconnected the Control board from the PS and repeated the test.
I noticed the difference in the relay clicks.
Before (with ctrl board connected) it would click "On" and after a moment click "Off"
After (without ctrl board) it clicks "On" and stays like that until I release the PS_ON jumper and only after I release it the relay clicks "Off".

This and the fact that panel flashed makes me feel like this is a fault Control board and not the PSU.

To make sure I would try to jump the 3.3v to the VS_ON pin of the PSU but I don't know how to do that.

[heavymachines]

Re: samsung plasmas & lightning

VS_ON is generated by the PS itself, right?
I thought VS_ON is coming from the control board so the control board may be at fault. Should I try to jump the VS_ON signal somehow and see if PSU will turn on fine?




Yes it is sent by ctrl board my bad , is the control board sending on signal to ps? at all?
https://www.badcaps.net/forum/showthread.php?t=22449
Here read this and elsewhere in these forums.

Going to let others throw their expertise on here. But we did narrow it down.

[heavymachines]

Re: samsung plasmas & lightning

I disconnected the Control board from the PS and repeated the test.
I noticed the difference in the relay clicks.
Before (with ctrl board connected) it would click "On" and after a moment click "Off"
After (without ctrl board) it clicks "On" and stays like that until I release the PS_ON jumper and only after I release it the relay clicks "Off".

This and the fact that panel flashed makes me feel like this is a fault Control board and not the PSU.

To make sure I would try to jump the 3.3v to the VS_ON pin of the PSU but I don't know how to do that.

What voltages are you getting on va and vs when ctrl disconnected?
Are you getting 3.3v signal at all from ctrl board? when connected?

[heavymachines]

Re: samsung plasmas & lightning

i have read here people using batteries or wall warts to supply voltage but never did that myself so i'll let others who have put their expertise on that subject.

[zape]

Re: samsung plasmas & lightning

Bad news.
I connected the main board and found 3.3v on one of the regulators. jumped the 3.3v to the VS_ON and I got correct Va voltage.
But after two seconds there was a loud POP and something went bad on the PS I guess.

[zape]

Re: samsung plasmas & lightning

Now I think the PS was faulty but protection was shutting it off.
When I forced the VS_ON protection did not help and it went from bad to really bad. I still get the Stand by though and the main board powers on with the remote.

[heavymachines]

Re: samsung plasmas & lightning

Overloaded it or shorted. Regulator probably dead er shorted open or fused. I wouldn't have done that, well do you know how to test regulators?

[heavymachines]

Re: samsung plasmas & lightning

time to check for shorts with ohm meter. Unplugged of course.

[zape]

Re: samsung plasmas & lightning

Traces to diodes blown on the Vs rail. Diodes are shorted. See photos
PS fuses are OK.
I believe regulators on the mainboard are ok too because it still turns on and off fine like it did before.
I did not check the voltage though.

SO I guess the diodes was bad from the beginning but overload protection turned the PS off.
After I forced the VS_ON the traces just blown.

[heavymachines]

Re: samsung plasmas & lightning

What the numbers off those , you test diodes with probes one way than the other way. but i bet they're certainly blown, it is possible you just found its weakness after turning it on and not overload the 3.3v line. it is up to you if you want to fix this at component level or replace the ps outright.

[zape]

Re: samsung plasmas & lightning

fcu10uc30
3 out of 4 are shorted.
Will try to source the replacement and restore the traces.

[heavymachines]

Re: samsung plasmas & lightning

fcu10uc30
3 out of 4 are shorted.
Will try to source the replacement and restore the traces.

I would remove them and see if you're reading shorts on those pads, quite possible it took other things out further down line. but make sure you record which ones went where, i'm assuming they're all the same part numbers.

[zape]

Re: samsung plasmas & lightning

They are simply a bridge rectifier made of pairs connected in a parallel.
Two big caps are connected down the line to the Y-Main connector.
Caps look good and the connector was unplugged. I also checked Y-Main board connector for short and it looks good.