On Sun, 2 May 2010 07:22:40 -0700 (PDT), saber850
wrote:

On May 2, 9:40*am, Meat Plow wrote:
On Sun, 2 May 2010 08:21:04 +0100, "N_Cook" wrote:



saber850 wrote in message
...
Hi,

My LCD desktop monitor has been exhibiting a problem for over 1 year.
It is out of warranty and I would like to fix it.

The problem is that the monitor displays the picture, and then
gradually fades to white, and then gradually fades to black.

The monitor does not exhibit the problem all the time. It comes and
goes. I do not have a procedure which triggers the problem; it seems
to be random. Sometimes it will behave this way for only a few
minutes, while other times it will behave like this for weeks.

I do not do anything to trigger the problem, other than have the
monitor powered on.

I have two of these monitors. I bought both monitors at the same time.
Both monitors are connected to the same video card (nVidia) via a DVI
connection. *Only one of the monitors exhibits the problem--the other
continues to function properly. *When the monitor exhibits the
problem, I can swap the DVI cables and the other monitor continues to
function properly. So I do not believe the problem is my video card or
computer.

I do not know of a method to get the monitor out of this problem
state. I've tried cycling the power to the monitor, and I've tried
rebooting the computer. Neither method fixes the problem. The only
thing I can do is wait for it to fix itself. But eventually, it
malfunctions again.

A video of the problem occurring is available he
http://www.youtube.com/watch?v=W7YpFZVRjcE

Best regards,
Nick

Can you observe discrete jumps in the fade, ie stepped.
Is it a backlight problem? if so perhaps find the brightness control line to
the inverter and break there and add your own subcircuit perhaps. First
monitor that line as maybe a fault inside the inverter chip

What brand/model monitor?
What brand/model card with NVidia chip?

Does the monitor have a DSUB I/O?
Does the video card have a DSUB I/O

The symptoms don't describe an inverter problem to me
but rather an LCD matrix drive, possibley PSU derived.

Both monitors are a Samsung SyncMaster 204B.
The video card is a ASUS EN7600GT.

The monitors have 1 DSUB I/O port and 1 VGA I/O port. I've only ever
used the DSUB I/O.
The video card has two DSUB I/O ports. Each one is connected to a
monitor.

As I mentioned in the OP, when the monitor is malfunctioning, I have
swapped the DVI cables between the monitors. When doing so, the
malfunctioning monitor continues to malfunction while the other
monitor (the one which has never malfunctioned) continues to function
properly. So from this, I believe the computer & video card are
functioning properly. Am I making a valid assessment here?

Is the PSU typically isolated from other circuitry in the monitor such
that it can be replaced?
The problem indicates an problem with the video controller IN THE
MONITOR. The Samsung 204s (and other Samsungs) have a bad reputation
for this reason. A slow fade to white can be a problem with the power
to the LCD panel itself, a fast fade to black can be caused by the
inverter. A slow fade to black MUST originate from the video
controler.

Open up the monitor, using all applicable precautions. On the video
controller should be several three terminal devices, but labeled with
a U number (as a hypothetical example, U404). Those are voltage
regulators. It is remotely possible that one of those may be putting
out an incorrect voltage. The last two digits in the part number will
be the output voltage. Again, a hyprtetical part number - L117N33B is
a 3.3 volt regulator.

PlainBill