Metro LCD with crispy cap.. 2 sec to black issue

[Solder Boy]

Hello all.. this is an offbrand LCD monitor made by Metro. Original symptom is 2sec to black issue. You can see the WIndows XP screen no problem before it goes away.

Opened it up and I could smell something burnt.. this is a first for me! One of the little blue capacitors had burnt to a crisp. It's neighbour is a 12J 3KV capacitor.

Looking for input here.. what would cause this cap to go poof? Bad transformer or bad CCFL? I probably have a replacement somewhere in my pile of boards.

Thanks!

[PlainBill]

Re: Metro LCD with crispy cap.. 2 sec to black issue

The caps in this position have been known to fail. The first step would be to replace it and let the monitor run for a few hours before buttoning it up and giving it an extended run.

PlainBill

[Solder Boy]

Re: Metro LCD with crispy cap.. 2 sec to black issue

Thanks Bill.. I have plenty of 3KV caps from other boards... will solder in another one and see what happens as you say.

I will report back when I've had a chance to do it.. too many other things on the go this week.

[PlainBill]

Re: Metro LCD with crispy cap.. 2 sec to black issue

Thanks Bill.. I have plenty of 3KV caps from other boards... will solder in another one and see what happens as you say.

I will report back when I've had a chance to do it.. too many other things on the go this week.

Make sure you match the capacitance (12pF).

PlainBill

[Solder Boy]

Re: Metro LCD with crispy cap.. 2 sec to black issue

Hi Bill.. well I got the 2 second to black issue solved.. I found an identical blue cap on another board. However I think the effort turned out to be a partial waste.

Fired it up and got these two white lines on the screen with a bit of black in the lower corner.

Took it apart again.. found 2 caps on the video board that were really bad so I replaced them.. fired it up same result.

Bad screen now?

[PlainBill]

Re: Metro LCD with crispy cap.. 2 sec to black issue

Hi Bill.. well I got the 2 second to black issue solved.. I found an identical blue cap on another board. However I think the effort turned out to be a partial waste.

Fired it up and got these two white lines on the screen with a bit of black in the lower corner.

Took it apart again.. found 2 caps on the video board that were really bad so I replaced them.. fired it up same result.

Bad screen now?

Yes. That is a bad panel.

PlainBill

[Solder Boy]

Re: Metro LCD with crispy cap.. 2 sec to black issue

Well I kinda figured the screen was toast.. just wanted confirmation.

Working on this thing wasn't a total waste.. learned something new working on this thing!

[jetadm123]

Re: Metro LCD with crispy cap.. 2 sec to black issue

Well I kinda figured the screen was toast.. just wanted confirmation.

Working on this thing wasn't a total waste.. learned something new working on this thing!

You can always part the monitor out and sell the power supply and video board to help compensate for your time spent doing the repair.

[Solder Boy]

Re: Metro LCD with crispy cap.. 2 sec to black issue

You can always part the monitor out and sell the power supply and video board to help compensate for your time spent doing the repair.

Normally I would agree with you however this is really an oddball of a LCD monitor.. it's a Metro and the PS board inside is pretty well propietary to this thing.. it's got oddball CCFL connectors.

I will likely gut it and put the working parts in static bags and keep them in stock for future reference.

[alexanna]

Re: Metro LCD with crispy cap.. 2 sec to black issue

Thanks Bill.. I have plenty of 3KV caps from other boards... will solder in another one and see what happens as you say.

I will report back when I've had a chance to do it.. too many other things on the go this week.

I just ran into one of these where one of the Blue caps next to the inverter transformer was burnt.
After replacing the cap the monitor worked, but after I powered the monitor down the inverter transformer where the failed cap was noticeably hotter than the other transformer.
It turned out to have the Hot wire at the CCFL barely making connection.
To check your work after your done either use a Temp. gun or your feeling of touch to see if the transformers are about the same temptaure. Oddly the blue cap was staying cool.
IF YOU USE THE TOUCH METHOD PLEASE UNPLUG THE POWER FROM THE MONITOR.
So to avoid a repeated failure, IF one transformer is noticeably warmer I would suspect wiring to the CCFL.

[Solder Boy]

Re: Metro LCD with crispy cap.. 2 sec to black issue

Thanks for the additional info will file that away for future reference. If someone hadn't have smacked the screen and damaged it I would have done more investigation.