42pf722a/37

[zukdj]

OK, the pictures attached will tell the story, the TV was working fine and then the next day started doing this. Some say its the logic (T CON) board since I have no flashing red lights to give me an indication of what went wrong. Any help would be greatly appreciated.

[zukdj]

Re: 42pf722a/37 problem with picture

OK, the picture attached will tell the story, the TV was working fine and then the next day started doing this. Some say its the logic (T CON) board since I have no flashing red lights to give me an indication of what went wrong. Any help would be greatly appreciated. Have to edit, the TV is a 42PF7220A/37

[tibimakai]

Re: 42pf722a/37

You need both Y buffer boards(~$125 on Ebay).

[zukdj]

Re: 42pf722a/37

How can I be sure? Is there a test to confirm, I was told it was the TCON main logic board.

[electronicsurplus]

Re: 42pf722a/37

Your problem is surely in the Buffers. Most likely the Upper buffer. You can test each buffer. Remove the 2 screws holding them to the chassis

Sometimes you can get away with only replacing the upper buffer and the set will work. BUT, may or may not be for long

It is highly recommended to replace the YSustain and, both buffers. often referred to as a Y-Trio or set. because, in these televisions a bad buffer can burn the YSustain and vice versa

Here's a very simple and easy method of identifying burned buffer boards LJ92-01203A / LJ41-02761A and LJ92-01202A / LJ41-02760A.
Those are the buffers for Y-sustain LJ92-01200A.

The trio is used in a great number of 42'' plasma TVs using Samsung plasma display technology (the display itself and the sustain/buffer boards).

It is also famous for its common failure. The most common scenario involves burning the Y sustain which subsequently burns one or both buffers.

Now, to the point: The most common defect in those buffers manifests itself in burning and shorting the power lines and some output lines.

The easiest way to detect if a board was burned is to measure the resistance between its power input and ground.

Normally it should be in the range of hundreds of kOhms and when burned it is usually a matter of Ohms.

In fact, you can use the diode/audio test mode to determine if a board is burned or not.

Still , in the below examples, I am using a multimeter in a standard resistance meter mode.

On the TOP buffer board, the power lines are the top two lins of the black connector and ground are the most of the remaining connetors.

On a good board the resistance between the two may be too big in the proper direction and about 500kOhm in reverse direction.

the board on this picture is good.

Here are some pics to show you more detailed

I have had a lot of luck with BLR Electronics in Calif and Coppell TV in Texas

Jon


On the bottom board the power lines are the bottom two lines on the black board and ground is above them.

In the example picture on the right the resistance there is only 4.4 Ohm clearly identifying this board as a burnout.

The resistance would typically be the same in both directions.

This board would prevent the TV from powering on and may also burn the Y-sustain board.

In a future post I'll also show how to identify the particular ICs on the burned board.

[electronicsurplus]

Re: 42pf722a/37

If you notice there are 2 pins that connect to the buffer, closest to the white connector which are separate and, there are 5 others soldered (Ground). Test across these points, One way you should get over 400K and infinite in the other direction, IF you show shorted then it is bad

[zukdj]

Re: 42pf722a/37

Thanks all, this one is fixed, 2 more in my garage to tinker with.

[budm]

Re: 42pf722a/37

So what did you do to fix it?

[zukdj]

Re: 42pf722a/37

New buffer boards.