Samsung PN58C550 Blank Screen with sound

[LarryU]

HELP, I have a three year old Samsung PN58C550 plasma TV. My daughter was watching it, walked out of the room and when she came back the screen was blank with the sound still playing. When you turn the TV on the red light blinks the samsung jingle plays you get a few sparkles in the middle half of the TV for a just a second then a blank screen no glow at all, the red light comes back on and stays on until you push another button on the remote then it goes off, normally the red light goes off when the TV is on and playing. I have been through Tom66's troubleshooting guides. Sounds like a Y-main or X-main right well I bought first a Y-main off E-bay with no luck then in order I replaced the power-board then the X-main then the logic main and finally the Tuner board. With none of them making any difference at all sound no picture. When I unplug the Y-main with the X-main plugged in no sound and the same with the Y-main plugged in and the X-main un-plugged in no sound. A little disclaimer on the tuner board the place I bought it from sent me a older revision number than what was in the TV, I don't know if it maters that much but because I read that with Samsung it does I have contacted the supplier and with a little hassle they are sending me the correct revision board. When I check the voltages on the power-board I am not getting any readings so it appears the the tuner board is not really turning on the TV which is the reason I replaced the power board before the X-main. I do not know where to go from here. Is the screen bad? If it were buffer boards then I should get some kind of picture so I'm stuck. I don't find any caps that look bad. I can post pictures if need. Any help and suggestions will be greatly appreciated. Thank you ahead of time for any help you can give me.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

Ok here are pictures of the TV and model tag.

[Mikeal007]

Re: Samsung PN58C550 Blank Screen with sound

Bump. I am having the same issue with a Sammy TV

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

See:
https://www.badcaps.net/forum/showpo...61&postcount=2

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

Thank you Tom66 for responding. I waited for the correct revision tuner board to come in and it didn’t make any difference, the TV does the same. I also followed your link and still same thing a few sparkles then nothing. I forgot to add that I had tried this before but didn’t disconnect the LVDS cable, but still nothing. So is it dead?

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

Well, a few sparklies is good, though it can indicate buffers, Y-main or X-main fault, it indicates -something- is working. When in a dark room, can you see screen glow (bare in mind for a plasma like this it'll be quite dark.)

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

No glow at all in a dark room after the sun has gone down so it was very dark. I have replaced the Y and X mains, but with used boards. One thing I don’t understand is that I’m not getting any Vs or Va voltage when the TV is turned on, I am getting a 15 volt reading from the 15 volt lines. I have tested all the power cables, in coming and distribution from board to board thinking maybe I had a bad power cable all show good. Something is not telling the power supply to turn on, which is why I replaced the control board and the tuner board thinking that one of these boards told the power supply to turn on. I have also tested the cable that goes from the remote control board to the tuner board it was also good. So what am I missing here.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

I need to modify my last post a little. I do have about 20 volts on the Vs line that decreases down to 10 volts slowly like a cap is bleeding off and then it will hold steady, it should have 210 volts. It seems like it tries to turn on (sparkles) then shuts the video down.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

I got the bright idea to unplug both Y and X main boards to see if the power supply would stay on. It didn’t but what I did discover was that I am getting 210 volts on the Vs and 55 volts on the Va but they both drain off quickly as the Tv starts and are over half way depleted before the jingle plays.

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

This may be normal. The newer Samsung sets detect unplugged Y-main/X-main and shut down the outputs. The fact that you briefly see them is good.

Help me out -- which board causes the voltage to go to zero?

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

Ok I plugged each board in individually and then both in and the response was the same. The volts seemed to bleed off a little slower with just the X main plugged in but not a big difference. I also did a factory reset and when I turn on the TV the red light goes out when the TV is on like it should.

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

Sounds like a main board issue, or a control board issue. Since you swapped the main board I'd be looking at the control board.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

I already had a control board that I put in and took back off when it didn’t do anything. I put it back on and still didn’t make any difference; voltage still bleeds off same as before.

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

Can you check pin VSON on PSU? It'll be on the connector going from the power board to the control board.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

VSON = 1.7mV I measured this on the control board end because there are exposed contacts on that end

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

As Vs/Va collapses, does this go high too? Just measure it while the TV makes the chime sound and see if it rises to around 3V.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

Yes it does, about 3 seconds before the chime it goes to 3.2 volts for about 2 seconds and then drops quickly.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

Tom66 where do I go from here?

[tom66]

Re: Samsung PN58C550 Blank Screen with sound

This indicates the control board is shutting down the power supply. It could be detecting a fault or it could be faulty itself.

[LarryU]

Re: Samsung PN58C550 Blank Screen with sound

I have two control boards and both are doing the same thing. So it must be a fault of some type. How do I figure out what's causing the fault.