# LCD power supply - Schottky or voltage regulator LM317t



## MeltManBob (Oct 10, 2010)

I have a Westinghouse LCM-22w3 I believe, eventually it stopped working. I finally got around to pulling the PSU and checking the capacitors which the 2200uf was visibly bad so I replaced it but this is where I'm pretty sure I ended up causing more problems. Prior to my first "repair" the monitor would turn the LED on and show "no signal" on the screen but would not show the computer booting up.

The PSU board is DAC-19m010. I replaced the 25v 2200uf with a 35v 1000uf and the monitor worked like normal for about an hour and then just shut off completely. I re-opened it and nothing looked different than when I replaced the capacitor. The LED will not come on and nothing will display on the screen. 

I was going to order the right capacitors from digikey but I checked here at radio shack and they actually had almost exactly what I needed to replace the typical capacitors on that board when they go bad. The 2 that didn't match exactly was the 10v 1000uf which was replaced with a 25v 1000uf and the 25v 1000uf I had put in place of the 2200uf was taken out and 2 new 25v 1000uf were put in, in parallel to get at least 2000uf.

At this point none of the fuses have blown and the transformer situated physically between the main input AC power parts and the capacitor bank is making it's barely audible high pitched noise so I know that power is getting at least to that point in the board. Beyond simple stuff I don't really know a whole lot about this but from what I've been reading I should consider the Schottky diodes and the LCM317T voltage regulator that are all with the capacitor bank.

I don't know why I didn't think to put 2 1000uf in parallel the first time but oh well, any help is greatly appreciated.


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## JimE (Apr 16, 2009)

You really need test equipment to isolate the trouble. While replacing obviously faulty parts will sometimes fix a problem. The obvious fault isn't always the actual problem...you are just seeing the weaklest link.


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## MeltManBob (Oct 10, 2010)

Like what kind of test equipment? How far can I get with a basic multi-meter? I would like to test the larger items since they are physically easier to replace on the board. Basically I'm wanting to do a bit more than just a cap kit before I shell out $50 for a new power supply from china. Any pointers?


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## JimE (Apr 16, 2009)

Schematics and an O-scope. You may make progress with a meter, but you would need to know if the voltages you are seeing are good or bad.


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## MeltManBob (Oct 10, 2010)

So in other words there isn't much else to do except buy a new board in terms of what is going to be cheaper considering money and time? I was hoping there were a few other parts that are common to go bad that I could check with the multimeter. Thanks.


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## JimE (Apr 16, 2009)

It may well be an easy fix. My point being, that simply poking about checking voltages isn't likely to get you anywhere. You need a way to know what you are seeing is good or bad. There are two ways for that, schematics (and likely better test equipment) or a good working unit so that you can compare one to the other.


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