Samsung pn51d440a5d: No Picture - Bad Logic Board?

[JDC]

Hello. Got a Samsung pn51d440a5d with no picture. When it turns on, you can hear a boot-up jingle. When it turns off, you hear another jingle. No obvious signs of bad caps.

According to this video from shopJimmy, I may have a bad logic board:

https://youtu.be/gnkyAGyI7GA?t=318

It'll cost me about 22 bucks to find out but I wanted to get some feedback before hand. Please share your experiences, if any. Thanks!

http://www.shopjimmy.com/samsung-bn9...ctrl-board.htm

[mmartell]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Doubtful. Measure the critical voltages first; Vs Va Vsc -Ve and Vb and check them against what's written on the panel sticker.

[tom66]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

More likely X- or Y-main, possibly Y-buffer. Check for cracks in the plasma panel.

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Replacing the logic board did nothing. Will follow both pieces of advice and get back to you two.

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

EDIT: I did this wrong. Vs Va Vsc -Ve and Vb readings are on the power board, I see. Looking into that now.

Panel has no cracks.

mmartel, I'm not sure I did what you asked correctly. There is a 6 wire cable running from the power board to the Y-sustain board. There is no sticker anywhere stating what the correct voltages are supposed to be (though I have seen this before).

With the TV plugged in and on, I measured the DC voltage using the metal parts of the cable connected to the Ysus. They are marked and were measured as follows using pin 3 as ground:

1 (VS) 20 - discharges slowly
2 (VS) 20 - discharged slowly
3 (GND)
4 (15V_GND) - 15.20
5 (GND)
6 (VA) 57 (discharges rapidly to 27, then slowly discharges.

How did I do?

(for anyone else with this model, I just now found this:



I'm going to look through it now. )

[Maklaud]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Start TV in autonom mode.
Read The Troubleshooting Manual.

[Maklaud]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Activating Power & Logic Board Test Patterns without Main Board.

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Alright, I think I located what mmartel was asking including the sticker he was referring to on the panel:

Using DC on my digital multimeter:

VS 205, shows 199
VA 58, shows 58
VSC -187, shows -187
VE 86, shows 86

These readings are the highest shown upon the TV powering on. From there, the readings discharge.

Maklaud, can you be more specific? It may be in the manual I mentioned above but I haven't made it that far.

EDIT: Looking into that now, Maklaud.

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Just did the Power & Logic Board Test Patterns without Main Board, nothing out of the ordinary other than no red light on the front nor start up sound. Logic board lights up in green.

[tom66]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Does the logic board LED flash around once a second or once every 5-7 seconds?

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

tom66: Doing the above mentioned power board tests or regularly?

[tom66]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Just have everything connected as normal

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

tom66: Once every 5 seconds it seems.

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Maybe the panel is garbage?

[tom66]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Probably not, but check for cracks in the glass. The smallest crack can stop the set from working

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Ill check again and get back to you.

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

No cracks to be found. The panel looks great.

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Taking a look at the backside of the YMain board, I see white smudges on the upper right part. Could water or heat have done this?

[Agent24]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Looks like flux residue from the factory to me

[JDC]

Re: Samsung pn51d440a5d: No Picture - Bad Logic Board?

Any other suggestions? Replace the Y-Main?