Samsung 204T syncmaster problem -- not bad caps

[mickgeyver]

I've got one of these that comes on and then the display fades out to
black after about 20-30 seconds. Turn off then on and same thing. When
opened up, I can see the CCFLs are brightly lit although the display
has faded to black. I replaced the power supply caps even though they
were not bulging so I don't have to deal with it later on. I swapped
in a converter board (the one with video inputs) and no joy. I opened
up the column driver board and blasted it with cold spray. I blasted
all boards with cold spray to see if the fade rate changed..... still
no joy. I've googled and bad caps seems to be the prevalent problem,
I am not using the DVI connector as I know there is a data rate
problem with the display blanking out..... Any clues or ideas for
whatever it is that I missed??

Thanks a bunch

al

 

[Dav.p.]

Sorry for my english and my low preparation, but u have checked the voltages on psu output,
before and after the blak screen? So u can find which board is the problem, it sounds to me
like a problem with the supply of the converter bd or mostly the lcd panel, find the lcd conn.
pinout and check if before and after the blackout there is the tipical voltage (5v..?)
Bye.

 

[mickgeyver]

On May 11, 8:20 pm, "Dav.p." <davi...@tiscali.it> wrote:

Sorry for my english and my low preparation, but u have checked the voltages on psu output,
before and after the blak screen? So u can find which board is the problem, it sounds to me
like a problem with the supply of the converter bd or mostly the lcd panel, find the lcd conn.
pinout and check if before and after the blackout there is the tipical voltage (5v..?)
Bye

I'm getting a good clean 13v from the power board and the regulators
on the converter board measure good as well. 5v, 3.3v, 2.5v. The power
good signal from the LM393 on board is in the correct state. I'm now
focusing on the column driver driver board as I seem to recall that
LCDs in general require +/- volts to make the pixels go on and off.
There is some regulator circuitry up there I've yet to explore.

al