Viewsonic LCD Monitor Problem

[prc1]

I have several VG150 LCD monitors (model VLCDS21457-1), and all
developed a problem just before the warranties expired. On a DOS
screen, I noticed that the bottom 1/4 of the monitor screen was
"lost", or appeared blank.
Hitting the return key on the keyboard would scroll the screen upward
to show the missing information. When the computer would first boot
(on the BIOS info screen), if a line of text landed at the right spot
on the screen, it would appear that the line would "echo" and repeat
part of the tops of the characters in the line all the way to the
bottom of the screen. And, somertimes on power-up,
the screen would not auto-size and would appear larger and out of
proportion. A power-off/power-on cycle would sometimes fix it. When
Windows loads the screen appears okay.

All of the monitors were returned for warranty service to Viewsonic.
Now two of the monitors are again exhibiting the same symptoms.

I wonder if the problem might be bad caps around the D/A converter as
was suggested by someone who'd serviced similar monitors (but not this
model)? Since the problem seems to appear only on DOS screens, could
the monitor just have a problem displaying particular sync frequencies
and not others?

Design flaw, or components that commonly fail? And if there are
commonly-failing components, what do I look for?
** To respond, remove the crap from my addy... **

 

[JANA]

I have had problems with a number of monitors of that model series. I used
an ESR meter to check the caps. I replaced all the ones that were reading
too high. These are SMD types, which can be ordered from most electronic
parts suppliers.

I have had a few monitors however, where the problem was more serious than
capacitors. In this case, the complete board had to be changed. The monitors
had to go back to Viewsonic for that, because they will not sell the parts.

--

JANA
_____


I have several VG150 LCD monitors (model VLCDS21457-1), and all
developed a problem just before the warranties expired. On a DOS
screen, I noticed that the bottom 1/4 of the monitor screen was
"lost", or appeared blank.
Hitting the return key on the keyboard would scroll the screen upward
to show the missing information. When the computer would first boot
(on the BIOS info screen), if a line of text landed at the right spot
on the screen, it would appear that the line would "echo" and repeat
part of the tops of the characters in the line all the way to the
bottom of the screen. And, somertimes on power-up,
the screen would not auto-size and would appear larger and out of
proportion. A power-off/power-on cycle would sometimes fix it. When
Windows loads the screen appears okay.

All of the monitors were returned for warranty service to Viewsonic.
Now two of the monitors are again exhibiting the same symptoms.

I wonder if the problem might be bad caps around the D/A converter as
was suggested by someone who'd serviced similar monitors (but not this
model)? Since the problem seems to appear only on DOS screens, could
the monitor just have a problem displaying particular sync frequencies
and not others?

Design flaw, or components that commonly fail? And if there are
commonly-failing components, what do I look for?
** To respond, remove the crap from my addy... **