55" Samsung No Display

[Loozer]

Re: 55" Samsung No Display

Yeah I hear ya. Ive fixed others in days. This one just don't want to live haha. Ill call and ask about the boards and let you know how it goes.

[tom66]

Re: 55" Samsung No Display

It is a very tricky project and I wouldn't be able to diagnose it without a scope to check the waveforms were good.

[Loozer]

Re: 55" Samsung No Display

Not yet I'm about to call them soon. I have to return the two other boards I bought and pick up that one or the buffer boards? Its becoming such a pain I may just junk it if that doesn't work.

[tom66]

Re: 55" Samsung No Display

That could be important, as I have heard that Samsung plasmas are very sensitive to revision numbers. I am well out of my depth here though, I've only done two Samsung plasmas... I mostly do LG chassis. Have you asked the seller if they can supply an AA1 to be sure?

[Loozer]

Re: 55" Samsung No Display

Sorry yesterday I was so busy. Now after looking I did notice some differences in the control boards. 1. On the orignal there is AA1 and the new one reads AA2. The pba # is the exact same on both. The pcb # is the same too. Only difference I can find is the AA#'s. I attached 3 pics of each board. Hope this helps. Thanks again tom.

[tom66]

Re: 55" Samsung No Display

Only with an oscilloscope.

Since you have bright light at least the Y-main, X-main and power supply are 99% guaranteed to be working (these only affect the picture - it's either there, or dim, or not at all.)

Since you have a bootup sound, the main board is probably (>90%) OK.

My suspects:
- Y-buffers (60%)
- Control (30%)
- Panel (10%)

You replaced the control board, and the light is brighter. Is the model on the control board exactly the same?

[Loozer]

Re: 55" Samsung No Display

Yeah its the exact same as before. No display no picture. Just static and now the vertical lines. Is there a way to diagnose the boards?

[tom66]

Re: 55" Samsung No Display

Have you got no picture at all? I am half suspecting the plasma panel is bad with those bright lines :/. It could be a Y-buffer problem but I can't be sure.

[Loozer]

Re: 55" Samsung No Display

So I ordered the new tcon board. installed it and fired it up. Now I get this picture. Am I getting closer to the problem? Still gray static with multicolor lines on right side.

[Loozer]

Re: 55" Samsung No Display

Hmm. Hopefully its not too much more expensive. I'm gonna order one and pray again .....

[tom66]

Re: 55" Samsung No Display

Huh; that makes me suspect the control board, because you -should- see something. Here is what one user reported:

Jumpered 4-2: Backlight (or plasma equivelant) would fire on for about 4 seconds then go off.
Jumpered 3-1: Backlight (or plasma equivelant) would fire on for about 4 seconds then go off.
Jumpered 2-1: Display would power on, show all gray for about 4 seconds, then go off.
Jumpered 4-3: This was the good stuff! Showed all types of test patters and then would loop itself indefinitely.

[Loozer]

Re: 55" Samsung No Display

And nothing. Stays the same except for 3 and 4 are connected

[Loozer]

Re: 55" Samsung No Display

No light it just turned off like yoy would hit power but I let go and the static came back. Ill try in a min thanks

[tom66]

Re: 55" Samsung No Display

That is normal, the PS-ON on this set is active-LOW, make it low to turn the TV on.

Are you saying the screen is lit up, but dark? This is an important clue and seems to eliminate the control, Y-main, X-main, Y-buffers and X-drivers. Maybe the test setting is different for this TV. Can you try all pin combinations?

[Loozer]

Re: 55" Samsung No Display

Also the screen blacks out when pins 3 and 4 are connected

[Loozer]

Re: 55" Samsung No Display

Alright and the ps-on from power supply to tcon reads 2.22 when plugged in. when actually turned on it reads .1? Is this normal?

[Loozer]

Re: 55" Samsung No Display

Found the pins and only the 4th one read .45 v. All rest read nothing

[Loozer]

Re: 55" Samsung No Display

Also I don't have a resistor unless you mean use one already on the board

[Loozer]

Re: 55" Samsung No Display

so I think I found it I tested the 1 on the power supply board reading ps-on and it read 2.22 v. Standby read 5v. I cannot find the 4 pins on the main board. May need some help findin them. Thanks as always here's a pic of where im at.

[tom66]

Re: 55" Samsung No Display

OK, the set does not power on, I half expected this, but some Samsung sets will still power on without the main board connected.

You need to find the pin marked PSON and connect it to the Ground (previously I said 5V standby; this was incorrect) with the 100 ohm resistor to limit the current.

Here's a thread where someone diagnosed a Samsung plasma with no picture -- including setting up the PSU:

https://www.badcaps.net/forum/showthread.php?t=21740

Then, you see that four pin connector on the control board? I believe pins 4 and 3 enable test mode... they must be connected together e.g. using a hard disk jumper or temporarily with a screwdriver or piece of wire.