samsung 50" plasma wont turn on

[Traviz28]

This is a Samsung 50" PN50C450 plasma tv.
These are its symptoms, it just suddenly turned off. When plugged into the wall, you can hear the relay clicking on and off five times before it stops and nothing else happens, no picture and no audio.
After removing the cover on the back of the TV, when plugged in, I can hear the relay on the power board clicking on and off, about one second intervals. Each time it clicks on, the green led on the logic board lights up, then the relay clicks again and the light turns off, repeat x5 before it remains off.
If I unplug the logic board ribbon cable that runs to the power board and then plug in the TV, It clicks on and I can hear the audio of the TV turning on but of course no picture because the logic board is not plugged in, If I plug in the logic board with the TV plugged in, the same 5x relay clicking resumes.
I replaced the power board, no difference, i replaced the main board because of some corrosion i noticed, no difference and lastly I replaced the logic board and still it does the same exact thing.
Any other ideas?

[tom66]

Re: samsung 50" plasma wont turn on

Can you supply some pictures of the internal circuit boards so we can indicate what to unplug and test.
Do you have a digital multimeter available and are you able to use it?

[Traviz28]

Re: samsung 50" plasma wont turn on

Thank you for your reply, Impressive signature by the way.
here are some pics I just took, I hope my iphone 4s quality is decent enough to help you help me.

I do have a multimeter (digital) and I know (mostly) how to use it

The third, fourth and fifth pics are pictures of components that have already been replaced and made no difference to the issue in my original post.

Pictures left to right are the whole tv, unknown board, power board, logic board, main board and another unknown board (z or Y buffers?)

[Traviz28]

Re: samsung 50" plasma wont turn on

ttt

[tom66]

Re: samsung 50" plasma wont turn on

OK there is a lefthand large board called the Y-main which is connected to green Y-buffers.
https://www.badcaps.net/forum/attach...4&d=1400833957

There is also a righthand large board called the X-main with the X-extender (sometimes called X-buffer) connected.
https://www.badcaps.net/forum/attach...8&d=1400833957

I want you to disconnect the power cable (thick 6 or so wire cable running between Y-main and power board) and see if the TV behaves differently. Do this with power OFF. Do NOT plug it in until you have left the TV unplugged for at least 1 minute to discharge.

[Traviz28]

Re: samsung 50" plasma wont turn on

Tom66, your a genius, I have been so concerned with the logic board issue and its oddities, i never thought to try unplugged power to the Y board. I am usually good at narrowing down the problem by trials of deduction.
I unplugged the power to the Y board and the tv clicked on, stayed on, sound also came on but of course no image. The green LED on the logic board was blinking green if that matters.

What is my next step? Unplug just the X board?

[Traviz28]

Re: samsung 50" plasma wont turn on

ttt

[tom66]

Re: samsung 50" plasma wont turn on

Yes, try just X-main unplugged and leave Y-main in, you may get a partial/poor picture or no picture.

[Firedragon76]

Re: samsung 50" plasma wont turn on

Hi! I am having the same problem with a PS42B435P2.
Seems to boot up when i unplugg y board. Have tried all other combinations.
Is there something I could measure on the y board?

[lbwarped]

Re: samsung 50" plasma wont turn on

I have this exact same TV, Samsung PN50C450, which powers on, but has a completely black screen. I measured all the voltages for Va, Vs, Vsc, and Ve, and all of them checked out fine. The main logic board's status LED blinks every 1 second in this state. I also tried disconnecting the X/Y-main from the main power supply, with no change in behavior except that the status LED stays illuminated for 5 seconds and blinks for 1, and the power supply voltage drops off after initially going up the normal level.

Can someone please provide some next steps to take in troubleshooting? Thanks!

[lbwarped]

Re: samsung 50" plasma wont turn on

Another thing that's complicating diagnosis is that the TV was set up to use external speakers. Is there a way to reset the TV so that it uses the internal speakers instead? Kind of difficult without being able to see anything on the screen.

[drussell]

Re: samsung 50" plasma wont turn on

Can someone please provide some next steps to take in troubleshooting? Thanks!

Since you seem to have normal voltages, try the logic board test. Disconnect the main board (with the input connectors on it) completely and jumper pin 3 and 4 of that 4-pin square test connector with the pins sticking out of the logic board together (easiest to use a jumper cap if you have one handy), then jump the PS-ON pin to ground (easiest to use a small wire on the disconnected power wire that goes to the main board) and see if you get test patterns on the screen.