Samsung PN58A550S1F No sound / Green squares

[packrat79]

Got this set in my repair shop, looks like a logic board failure but I thought I'd get a second opinion before ordering a replacement. Set powers but power light remains blinking, has two squares on the screen (see photo) but no sound. Buttons produce a beep when pressed but don't do anything. Logic board has two diagnostic LED's that blink rapidly. All voltages from the PS measure correctly.
Any opinions?

[DXseekerMO]

Re: Samsung PN58A550S1F No sound / Green squares

Funny, those almost look like one of the test patterns built in to the logic/main board.

[mmartell]

Re: Samsung PN58A550S1F No sound / Green squares

Run the test patterns.

[packrat79]

Re: Samsung PN58A550S1F No sound / Green squares

How do I run the test patterns? I don't see any info on this in the service manual.

Something that concerns me is the fact that I can't turn the power off / on with the buttons... do you think this could be a mainboard issue, or is the mainboard trying to communicate with the logic board and getting stuck?

[dick_barton]

Re: Samsung PN58A550S1F No sound / Green squares

Post some sharp focused photo's of your circuit boards to start with.

[packrat79]

Re: Samsung PN58A550S1F No sound / Green squares

I'll try and get more photos if I have time. Looking around, I see there is a common fault with this mainboard which can cause similar symptoms (power light blinking indefinitely, no video), so I'm really leaning that way now. Tried disconnecting the LVDS cable from the main to logic board, and the LED's on the logic board continued blinking as before. Maybe an indication that they aren't getting any signal.

[dick_barton]

Re: Samsung PN58A550S1F No sound / Green squares

The disconnecting of the ribbon cable to the mainboard is part of the screen test pattern setup but you also have to make a link on the logic board which hopefully a photo will show where the link should be made.

[packrat79]

Re: Samsung PN58A550S1F No sound / Green squares

Didn't have time to take any more pictures, but it is identical to the one shown here:

http://www.coppelltvrepair.com/p/103...oud-screeching

[dick_barton]

Re: Samsung PN58A550S1F No sound / Green squares

Lovely picture but it isn't the logic board where the link has to be made as per my earlier comment.

[packrat79]

Re: Samsung PN58A550S1F No sound / Green squares

Oops, that is the mainboard, my mistake. Here is the logic board:

https://www.ebay.com/p/Samsung-Pn58a...02a/1219768041

[tvtimmy]

Re: Samsung PN58A550S1F No sound / Green squares

In the red circle, short pins 3 and 4. Make sure ldvs cable is unplugged(in white).

[packrat79]

Re: Samsung PN58A550S1F No sound / Green squares

OK gave it a try, posted a picture of the result. Those two bars are still present, but everything else is a solid color which cycles from white to red to green.... then the TV power cycles off and on (something I forgot to mention in my original post) and it starts over again. I suspect blue would be the next color in the sequence.
The power cycling suggests the mainboard (this is a known fault), but the fact that the two bars are still present worries me that the logic board may also be faulty. Any ideas?