Samsung PN50A510 P3FXZA Plasma Cycling On/Off

[kevinm34232]

When first plugged in the TV clicks and screen glows gray, then cycles off and on again several times until it says on with a loud buzzing noise from speakers and distorted pic.

I disconnected LVDS cable and jumpered pins 3 and 4 of logic board, which results in the test pattern showing, but still continues the cycling on and off, so basically I get a solid white, then red, then green screen from the test pattern before the TV restarts itself and repeats until the buzzing happens.

It never gets past the third solid green test screen even when buzzing starts. You can also see some pixels flickering in the solid screen.

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

After watching it reset over and over I saw it once or twice go past the solid green screen to blue screen before rebooting. Also Im now hearing the startup chime which I don't beleive I was hearing before, and at the moment no loud screeching.

Also on logic board, only 1 LED blinks once per second (LED2000), the other (LED2001) briefly flashes when plugged in, but goes out and stays out.

EDIT:
Found some info on removing harness from PS to main board, and jumpering PS_ON pin to ground pin on the PS. This keeps the TV on and test pattern going continuously.

Sound like a bad main board?

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

These main boards are pricy and not plentiful, can anyone confirm this looks like a bad main before I order it? Thanks!

[attainteddragon]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

if you can get test patterns, then it can only be the main!

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

I replaced the main with a board from ModusLink, and the TV came on. After testing for a few days, the last 2 mornings when turning the TV on from being off overnight, it shows a distorted picture like below, and after a few seconds, cycles off and back on again several times until the picture finally becomes normal.

This is what the original owner had described happening to me as well. Any thoughts?

[tom66]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

The test patterns are good on the logic with this fault? Could be the main board you got is also going bad.

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

I don't know I guess Id have to set up the test patterns first thing in the morning before turning it on and see. Could it also be the logic board or something loose?

[tom66]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

If the test patterns are good it's probably not going to be the logic board. Especially if the TV is power cycling.

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

Since this seems to happen when TV was cold I was experimenting with the freeze spray on the main board. After some isolating, it seems like when I freeze the two IC's in the pic, that the problem happens. I tried to isolate to one but can't. After the defrost it usually comes back on normally.

[tom66]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

That seems possible. They are the RAM chips for the video processor. It is a very common issue with this model. You could try reflowing them with hot air and flux, but I would not expect that repair to last.

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

I will give it a try.. How are the pins arranged underneath all I see is a black rectangle. And it seems to be the top one.

[tom66]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

Typical pin layout

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

What temp would you set the hot air station to? Ill try it on the old board.

[tom66]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

230°C is typical. That being said, I would not want to sell on a TV with a reflowed main board, due to the high possibility of future failure in just a few months.

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

I agree. I want to try it on the old board just to see, and Im sending the ModusLink board back for replacement.

[tom66]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

Remember to use plenty of flux! It's nearly impossible to use too much flux.

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

Should I use something to press on the chip when heating it or no?

[tom66]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

Not usually required. Just remember to circle heat between the areas and swap between chips every 10 seconds -- you're not trying to remove them! I recommend around 3 minutes of heating.

[kevinm34232]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

Tom, I tried the reflow, did not work. It seems the person I got this TV from had the same issue I am having now (with the new board) and it got progressively worse, perhaps eventually corrupting the eeprom from all the on/off cycling to where it won't come on at all.

We will see what happens with the next board and if I get a chance will ask a tech at ModusLink and see if they can provide any info..

[tom66]

Re: Samsung PN50A510 P3FXZA Plasma Cycling On/Off

After you do get the new board, I'd advise some fix-on heatsinks for the RAM to give them better longevity.