LCD monitor troubleshooting


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Old 02-04-11, 05:55 PM
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LCD monitor troubleshooting

With no warning, my LCD monitor stopped displaying. I connected it to a different computer and it didn't work there, either. I put a volt meter on the power supply, and it's delivering 5 volts as expected. When I connected it to a computer that was already running, I noticed the monitor flashes on for an instant, then goes black again. If I cycle the power switch again it flashes on for an instant, then black.

Any chance to revive this? Or is it done for good?

Thanks,
Dave O
 
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Old 02-05-11, 04:53 AM
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What's the make & model number?

Look closely at the screen with the computer connected and everything on. Use a flashlight if necessary. If you see a picture but it's very dark it's probably the inverter. The fact that it flashes on once in awhile means it's probably not the lamp.

Replacing the inverter isn't difficult and they aren't very expensive.
 
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Old 02-05-11, 05:43 PM
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Make / model is Microtek c593. (I've never heard of it before either.) I'll look for an inverter- thanks for the tip!

Dave O
 
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Old 02-05-11, 07:35 PM
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I would check the capacitors in the power section. There have been many failures of computer monitors and flat screen tv's from leaking,swollen electrolytic capacitors. I have repaired 4 of 5 monitors given me and they all suffered from bad caps. They were all different brands so its a component problem rather then a manufacture or model problem.
The inverters and back lights can also be a issue in monitors but that type failure is more common with laptops.
 
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Old 02-06-11, 06:39 AM
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Originally Posted by CycleZen View Post
Make / model is Microtek c593. (I've never heard of it before either.) I'll look for an inverter- thanks for the tip!

Dave O
Don't buy an inverter if you can't see a picture on the screen with a flashlight.
 
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Old 02-06-11, 05:35 PM
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I did the flashlight test, and the screen was displaying the DIY.com web page as expected- so according to your post, it suggests the inverter.

I need to admit ignorance on this topic and ask clarification: what / where is the inverter you're talking about? A quick web search says an inverter converts DC to AC power. The DC power supply (plugged into a wall socket and into the back of the monitor) is delivering 5 volts DC according to my multimeter: are you referring to a different component? Or is "inverter" a catch-all term that also indicates AC to DC power conversion?

IDMason60- I'm intrigued by your response. How do I test for bad capacitors?
 
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Old 02-07-11, 04:09 AM
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The inverter board supplies the high AC voltage required to drive the fluorescent backlight in an LCD screen. It is converting DC to AC and stepping up the voltage (typically to around 1,000 volts).

Speaking of voltage, the Microtek website says that model requires a 12-volt power supply. Are you sure you're using the correct supply? Is there a label near the power supply connector that states how many volts/milliamps it requires?
 
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Old 02-07-11, 06:22 PM
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Dave
The monitors I repaired and the caps I replaced didn't need testing. They were swollen up and leaking and a couple were discolored. I simply replace what I knew did not look right and was bad. I was lucky and was able to restore 4 monitors out of 5. The last one had color issues.
It sounds like you have a entirely different issue and are on track with getting it figured out.
I replaced a inverter board and the back light in a laptop. The parts in that case were fairly small and fragile. That was about as small as my eyes could handle.

Good luck with your DIY project. When working with inverter board and back lights you will be working with high voltage. Be careful and make sure its all turned off and give things time to bleed off and discharge.

Larry
 
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Old 02-15-11, 02:03 PM
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Apologies for the delayed response

Sorry I haven't been back to this site for a while: life keeps getting in the way.

I"ll have to check the power supply: I picked up the supply that was connected to the monitor, checked what output it is supposed to deliver (on the label) and then tested it with a volt meter. The power supply was delivering its rated voltage- but I did NOT check to see if that power supply was intended for this monitor. I'll check that when I get home- the kids might have disconnected something and swapped power supplies, who knows.

Larry, thanks for the tip about capacitors: it would be cool to fix a dead monitor with a trick like that!
 
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Old 02-15-11, 05:34 PM
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Argh!
As suspected: one of the kiddos switched power supplies. The monitor was just under powered, and now it's working normally.

But- to both Rick and Larry- I enjoyed our conversation anyway. As usual I'm a little bit smarter for talking to the DIY.com gurus. Thanks!

Dave O
 
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Old 02-15-11, 08:35 PM
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Thanks for posting back with the solution.

For the record, a power supply can read proper voltage with a meter when it's not connected to anything, but the minute you put it under load a malfunctioning supply can drop to 0 volts. For this reason you should always check them under load. The same applies to batteries.
 
 

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