Samsung PS42e92HX black display problem

[adriancel]

Hello,

I have a very strange problem with this plasma TV.
This TV arrived to me whit 2 caps swollen in the PSU which I changed.
After power on the sound is OK, it responds to the remote control but the display remains black. After that I've checked again in a dark room and the display is turning ON and remains light (very dim).
On the display is not any trace of the OSD.
I've measured Vs (207V measured, 205V on the panel sticker), Va (63V - 63V).
I've measured Vscan = -190V (Vs = -190V on the panel sticker).
I've tested the FET's from the YSUS and ZSUS board and all of them are OK.
After the TV sat on for 30min I've checked the temperature of the Y buffers and all of them are cool.
What could be the problem with this TV?

Thank you.

Very sorry for the crappy pictures and my English.

[tom66]

Re: Samsung PS42e92HX black display problem

Your English is fine.

In this picture you have CN2023 (four pin block) and CN2021 (LVDS connector.)

I do not see LVDS connected, on CN2021, is this cable missing or just unplugged for this photo? If it is missing, you will need to find a replacement, as a missing cable could cause this fault.

You can activate the test pattern mode on this panel by placing a jumper across pins 3 and 4 of CN2023 (with power off) and leaving the LVDS disconnected. When you do this, after turning the set on, you should see patterns like this, though it may vary slightly.
http://www.youtube.com/watch?v=JCtF53GKE0A

If the test patterns appear, the only fault can be the cable or main board, the main board is this board:
https://www.badcaps.net/forum/attach...8&d=1375304644

[adriancel]

Re: Samsung PS42e92HX black display problem

The LDVS cable was disconnected by me to take the pictures.
I have done the test with CN2023 (short 3-4) and there is nothing on the display - black screen.
This means that the control board is defective?

[tom66]

Re: Samsung PS42e92HX black display problem

Can you see a point to test Va voltage? Should be around 60V on these sets.

And a picture of the overall chassis would help.

So far does sound like control board fault.

[adriancel]

Re: Samsung PS42e92HX black display problem

On the PSU there is a pin (for measurement I suppose) Va.
On the panel sticker Va = 63V.
Measured Va = 63.8V.
Va is going only to the ZSUS board.

[tom66]

Re: Samsung PS42e92HX black display problem

Va should go the X-buffer boards (lower boards on bottom of panel.) Caution, do not disconnect or reconnect Va while the set is running. Please post a picture of the chassis.

[adriancel]

Re: Samsung PS42e92HX black display problem

I have mesured the voltage on the fuse (the fuse is OK) from the X Buffer board and I have 63.7V

[tom66]

Re: Samsung PS42e92HX black display problem

You have 63.7V both ends of fuse? OK, assuming you did the control board test correct, the control board is the likely fault.

[adriancel]

Re: Samsung PS42e92HX black display problem

Thank you very much.
I guess another plasma bites the dust.

[tom66]

Re: Samsung PS42e92HX black display problem

Well, the control board is easily replaced...
Plasmas tend to be slightly more reliable than LCDs.