ACER 1916B LCD Monitor won't start when cold

[Tim]

It seems this 19" LCD won't start up when it is cold. If you leave it
for a bit then it will eventually start up. The customer reported that
it had a swimming effect, but I did not see that happening. I did notice
that the backlight seemed to dim and brighten on it's own once in a
while.

I'm assuming that the CCFL tubes or the inverter are the cause of the
dimming, but the startup problem is weird. The screen blinks the LED and
you hear a high voltage like squeak and the lcd flashes bands
momentarily, but no pic or menu is displayed. After it gets warmed up,
it will run for days without incident.

I really hate to throw this one out without trying to solve it's
problems. It's a 2005 model.

Any ideas out there?

- Tim -

 

[James Sweet]

It seems this 19" LCD won't start up when it is cold. If you leave it
for a bit then it will eventually start up. The customer reported that
it had a swimming effect, but I did not see that happening. I did notice
that the backlight seemed to dim and brighten on it's own once in a
while.

I'm assuming that the CCFL tubes or the inverter are the cause of the
dimming, but the startup problem is weird. The screen blinks the LED and
you hear a high voltage like squeak and the lcd flashes bands
momentarily, but no pic or menu is displayed. After it gets warmed up,
it will run for days without incident.

I really hate to throw this one out without trying to solve it's
problems. It's a 2005 model.

Any ideas out there?

- Tim -

First thing I'd check is electrolytic capacitors in the power supply and
throughout the rest of the monitor. Cold faults are the classic symptom of
bad capacitors, I wouldn't be surprised if you find some of them bulging or
leaking onto the PCBs.

 

[Tim]

First thing I'd check is electrolytic capacitors in the power supply and
throughout the rest of the monitor. Cold faults are the classic symptom of
bad capacitors, I wouldn't be surprised if you find some of them bulging or
leaking onto the PCBs.

Well I got the monitor opened up, and I found 5 jiffy popped
electrolytics, all on the PS board, and all the same value (470uf @ 25V,
made by CapXon). All the other caps look excellent. I'll replace those
puppies, and let you know the outcome. I think I'll try to put in some
with a bit higher voltage, if I can find some that will fit into the
enclosure.

Thanks for the heads up,

- Tim -

 

[James Sweet]

Well I got the monitor opened up, and I found 5 jiffy popped
electrolytics, all on the PS board, and all the same value (470uf @ 25V,
made by CapXon). All the other caps look excellent. I'll replace those
puppies, and let you know the outcome. I think I'll try to put in some
with a bit higher voltage, if I can find some that will fit into the
enclosure.

Thanks for the heads up,

- Tim -

Same voltage should be fine, those caps likely came from the infamous
electrolyte scandal of a few years back. Make sure you scrub off the goo.

 

[Jim Yanik]

Same voltage should be fine, those caps likely came from the infamous
electrolyte scandal of a few years back. Make sure you scrub off the
goo.

he probably should use low ESR,105 degF switcher-grade caps,too.

 

[James Sweet]

he probably should use low ESR,105 degF switcher-grade caps,too.

Won't hurt, though I think people obsess over the 105 degree (it's C, not F)
thing, if anything in a monitor is approaching 100C, something is wrong.

 

[ZACK]

yup seen this in power supplies- motherboards.
the caps that come from china i call them
chinese crackers.

 

[Tim]

Same voltage should be fine, those caps likely came from the infamous
electrolyte scandal of a few years back. Make sure you scrub off the goo.

OK I replaced the bad caps. There wasn't any goo on the PCB at all. The
final count was 3 x 470uf 25v and 2 100uf 10v. The ones I had were a
higher voltage, but they fit ok. The monitor came right up and seems to
be fully functional. I am using it as my shop monitor right now.

Thanks for your help, James.

- Tim -