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Electronics => Beginners => Topic started by: DARKFiB3R on October 22, 2012, 06:05:41 pm

Title: LC200A LC Meter suitability
Post by: DARKFiB3R on October 22, 2012, 06:05:41 pm
Hi guys, I could do with some help fixing my PC monitor.

When I turn it on, an image flashes on the screen for a moment, then it goes dead. From what I gather, this points to one or more of the caps being bad. I've had a good look, and they all look fine though :/

I've uploaded some pics, if anybody would care to take a look (sorry for the poor quality).

http://img5.imageshack.us/img5/484/dsc06352j.jpg (http://img5.imageshack.us/img5/484/dsc06352j.jpg)
http://img33.imageshack.us/img33/7061/dsc06353a.jpg (http://img33.imageshack.us/img33/7061/dsc06353a.jpg)
http://img502.imageshack.us/img502/7972/dsc06354p.jpg (http://img502.imageshack.us/img502/7972/dsc06354p.jpg)
http://img802.imageshack.us/img802/6461/dsc06355e.jpg (http://img802.imageshack.us/img802/6461/dsc06355e.jpg)
http://img713.imageshack.us/img713/4412/dsc06356y.jpg (http://img713.imageshack.us/img713/4412/dsc06356y.jpg)
http://img442.imageshack.us/img442/4096/dsc06357c.jpg (http://img442.imageshack.us/img442/4096/dsc06357c.jpg)
http://img717.imageshack.us/img717/3719/dsc06358kb.jpg (http://img717.imageshack.us/img717/3719/dsc06358kb.jpg)
http://img716.imageshack.us/img716/8021/dsc06359v.jpg (http://img716.imageshack.us/img716/8021/dsc06359v.jpg)
http://img69.imageshack.us/img69/1687/dsc06360gy.jpg (http://img69.imageshack.us/img69/1687/dsc06360gy.jpg)
http://img404.imageshack.us/img404/79/dsc06361qx.jpg (http://img404.imageshack.us/img404/79/dsc06361qx.jpg)
http://img690.imageshack.us/img690/6295/dsc06362tq.jpg (http://img690.imageshack.us/img690/6295/dsc06362tq.jpg)
http://img267.imageshack.us/img267/4265/dsc06363u.jpg (http://img267.imageshack.us/img267/4265/dsc06363u.jpg)
http://img543.imageshack.us/img543/4386/dsc06364r.jpg (http://img543.imageshack.us/img543/4386/dsc06364r.jpg)
http://img717.imageshack.us/img717/1290/dsc06365o.jpg (http://img717.imageshack.us/img717/1290/dsc06365o.jpg)
http://img210.imageshack.us/img210/5230/dsc06366f.jpg (http://img210.imageshack.us/img210/5230/dsc06366f.jpg)
http://img826.imageshack.us/img826/8417/dsc06367ky.jpg (http://img826.imageshack.us/img826/8417/dsc06367ky.jpg)
http://img31.imageshack.us/img31/5376/dsc06368l.jpg (http://img31.imageshack.us/img31/5376/dsc06368l.jpg)
http://img90.imageshack.us/img90/7129/dsc06369e.jpg (http://img90.imageshack.us/img90/7129/dsc06369e.jpg)
http://img515.imageshack.us/img515/6750/dsc06370c.jpg (http://img515.imageshack.us/img515/6750/dsc06370c.jpg)
http://img715.imageshack.us/img715/417/dsc06371r.jpg (http://img715.imageshack.us/img715/417/dsc06371r.jpg)
http://img685.imageshack.us/img685/5302/dsc06372wn.jpg (http://img685.imageshack.us/img685/5302/dsc06372wn.jpg)
http://img607.imageshack.us/img607/6404/dsc06373q.jpg (http://img607.imageshack.us/img607/6404/dsc06373q.jpg)

Anyways, after watching these two videos, I have a half decent idea of what I need to do...

www.youtube.com/watch?v=Ytw57212X2o (https://www.youtube.com/watch?v=Ytw57212X2o#ws)
www.youtube.com/watch?v=72sJ5Infuu0 (https://www.youtube.com/watch?v=72sJ5Infuu0#ws)

So what I really want to know at the moment, is if the LC200A is up to the job of testing these caps.

Any help and advice would be much appreciated.

Thanks :)
Title: Re: LC200A LC Meter suitability
Post by: w2aew on October 22, 2012, 07:30:13 pm
It's hard to say whether this is a case of bad caps or not, but definitely worth checking out.  The LC meter will only give you a reading on the capacitance value.  As these caps start to dry out, many times the ESR will increase more dramatically than any change in the capacitance value.  Will bad caps show up as having the wrong capacitance value - possibly.  However, dried out caps with high ESR may read ok for their capacitance, so you really want to be able to measure that.  The LC200A won't help you with that as far as I know.
Title: Re: LC200A LC Meter suitability
Post by: kripton2035 on October 22, 2012, 07:37:07 pm
Quote from: w2aew on October 22, 2012, 07:30:13 pm
It's hard to say whether this is a case of bad caps or not, but definitely worth checking out.  The LC meter will only give you a reading on the capacitance value.  As these caps start to dry out, many times the ESR will increase more dramatically than any change in the capacitance value.  Will bad caps show up as having the wrong capacitance value - possibly.  However, dried out caps with high ESR may read ok for their capacitance, so you really want to be able to measure that.  The LC200A won't help you with that as far as I know.
++1
Title: Re: LC200A LC Meter suitability
Post by: PA0PBZ on October 22, 2012, 07:42:46 pm
Quote from: DARKFiB3R on October 22, 2012, 06:05:41 pm
When I turn it on, an image flashes on the screen for a moment, then it goes dead. From what I gather, this points to one or more of the caps being bad. I've had a good look, and they all look fine though :/

Isn't it just the backlight that is failing? Get a flashlight and see if the picture is still there.
If that is not the problem, try to find out what the voltages from the power supply should be (CN701) and measure them.
It's highly unlikely that any caps on the signal board are causing this, if there are bad caps they are on the power supply but I agree that there are not many and they look ok.
Title: Re: LC200A LC Meter suitability
Post by: DARKFiB3R on October 24, 2012, 10:13:13 pm
Thank you for the replies.

I was under the false impression that the LC200A was indeed an ESR meter. I don't know much about these things, but I guess that is obvious  :-[

I did the flashlight test back when the monitor first failed (it's been in the loft for a while now), and there was no image coming through. I have repaired laptops in the past with that issue, so I know what to look for there.

At this point, I think it would be easier and cheaper to just replace all the caps, and see how I get on.

Thanks again :)