Samsung PN60F5500AF Power-on Problem

[AGorowski]

I picked up a Samsung Plasma 60" tv not working. It has backlight, and standby power, but powering on just gives 5 flashes on the front LED. On the main board, when power is turned on, the green LED will flash 13 times, pause, and then flash 2 times. After a few seconds it will repeat. I've tested the PS and Y-SUS board voltages, with the following results: While the TV is in power-up mode (13 green LED flashes) the measured voltages are at or near recommended voltages. However, during the pause and 2 LED flashes the voltages drop to new levels on the PS and rise to new levels on the YSUS as listed. Once the green led cycles back to the 13 flashes, the power levels return to normal.

Vs - 209v drops to 165v (sticker on tv says it should be 208)
Va - 57v drops to 36v (should be 57)
VSc - -195v rises (or drops, depending on how you look at it) to -207v (should be 195)
Ve - 112 to 118 (should be 113)

Resistance testing on the Y buffer test points shows resistance in the Mega-ohms, which I understand is what is supposed to be.

Voltage on Pon is 6v during standby, but drops to .8v or so when the power button is pressed.

I forced a color test by jumpering pins 3 and 4, and screen cycled, but only through grey, red, and black - no other colours or patterns.

I have no schematics or manuals, but I'm suspecting the main board (BN94-06194B) but would appreciate any advice or comments before I go board hunting. The PS board is PS1FF-DSM and the Y-Sus board is LJ41-10331A (Rev 1.1)

Attached is a pic of the PS board, if that helps.

[dick_barton]

Re: Samsung PN60F5500AF Power-on Problem

Reading through the threads on the Forum it appears that if it successfully cycles through the test pattern and repeats without the set switching off, tends to indicate a mainboard fault.


Edit.
I see that the logic board is integrated into the mainboard. But if it's working when you force a colour test then it would look like a mainboard fault since your power supply must be working correctly to display the image on the screen.

[AGorowski]

Re: Samsung PN60F5500AF Power-on Problem

Update:
I pulled the main board, and checked it for obvious flaws. One of the inductors had some questionable solder connections, (see pics 1 and 2). Touched the solder joints up and re-installed the board. Now when the system comes on, half the screen comes up with vertical lines. The lines stay the same whether or not the main board is jumpered for the test screen or not.

[dick_barton]

Re: Samsung PN60F5500AF Power-on Problem

I would double check that all the connectors have been reinserted correctly.

[AGorowski]

Re: Samsung PN60F5500AF Power-on Problem

Good call;

Turns out one of the ribbon cables was not seated properly. Still, it shows some activity on the screen, but clearly the inductor was not at fault. May wind up just breaking down and replacing the main board.

[dick_barton]

Re: Samsung PN60F5500AF Power-on Problem

Does the pattern test still work and cycle repetitively through the colours?

[AGorowski]

Re: Samsung PN60F5500AF Power-on Problem

Just the grey red and black full screen. No other colours.

[dick_barton]

Re: Samsung PN60F5500AF Power-on Problem

Just the grey red and black full screen. No other colours.

But are they clear of lines or distortion of any kind and does the colour pattern repeat because if so then it looks like to me that you still have a mainboard fault.

[AGorowski]

Re: Samsung PN60F5500AF Power-on Problem

No distortion. Solid colours filling the whole screen. Sequence is black, grey, red, and back to black. Each screen stays on for about 10 seconds.

[dick_barton]

Re: Samsung PN60F5500AF Power-on Problem

So it is looking like a mainboard fault unless anyone else can think of what else could be wrong.

[AGorowski]

Re: Samsung PN60F5500AF Power-on Problem

Thanks Dick. I've ordered a new mainboard, and will update once I've tried it out. I'm hoping that's the only problem.

[dick_barton]

Re: Samsung PN60F5500AF Power-on Problem

Me too. I hope my diagnosis is correct.

[AGorowski]

Re: Samsung PN60F5500AF Power-on Problem

Lol. It's a little bit of logic and a little bit of luck...

[AGorowski]

Re: Samsung PN60F5500AF Power-on Problem

UPDATE:

Just installed the new main/logic board. That appears to have been the problem. It starts up fine, responds to the remote, etc. I'll put it all back together and give it a full run up to make sure its all working, then give it a bit of run time to make sure its not a short-term fix. Thanks for your help Dick!

[dick_barton]

Re: Samsung PN60F5500AF Power-on Problem

Thanks for the follow up. Will be of help to others.