trouble IDing cap and best way to remove it?

[justchad]

hey all,

I have an LG LCD (flatron e2242t-bn) and here are some pics of the boards and the issues I've found http://imgur.com/a/3Wnly
The big cap
looks domed up a bit so I think that might be the main problem, but I'm not sure what the specs are for it, is it really a 100v? but I also noticed the mess in the first pic once
I flipped the board over and think I will have to clean that up also (maybe just solder wick it? to clean up the mess?) the flip side of that mess is in about this area.

Is that voltage regulator likely bad or is it likely to be ok?

What do you all think?

[ben7]

Re: trouble IDing cap and best way to remove it?

1. The cap is made by Samyoung. I've noticed SMD caps like that to have a top that isn't quite flat, so it might be good. Only way to tell is to see if it has its rated capacitance and ESR.

2. Looks like flux. Seen it like that on boards before.

3. Can't say. The only way would be to check it.

[mariushm]

Re: trouble IDing cap and best way to remove it?

Based on the 33 at the end and lack of adjusting resistors in the vicinity, the regulator in the third picture is a 3.3v one.

The 8 pin SOIC chip to the right of this linear regulator works with that inductor (the one that says 100 DK mC on it) and some capacitors and resistors around it to form a dc-dc converter... see the datasheet for that chip or at least measure the voltage between ground and a leg of that inductor .. or follow the traces from that inductor which should lead you to a capacitor that you should test.


The capacitor in the first picture is 33uF 100v rated ... when checking ESR don't expect low esr, values like 0.2-0.4 ohm, maybe even more, would be reasonable for such capacitor.

2nd picture... that's just solder added to the copper area as a way to increase the thickness of the pcb and in a way dissipate heat a bit better. Your only concern should be about that bit of solder on the right side not shorting the copper in that square with lots of vias to the copper outside that square.
It looks like there's silkscreen and insulation there so it's unlikely there's a short. Still if you're paranoid you can just get your soldering iron and warm that extra solder and drag it away to make a clear demarcation between the copper pours.

Anyway, what's wrong with the monitor? You don't say...

[justchad]

Re: trouble IDing cap and best way to remove it?

Anyway, what's wrong with the monitor? You don't say...

Sorry was getting ahead of myself there. It sat for about a month in about 10 deg weather (in weather tight detached garage) and when I brought it in I let it sit for a day, and then hooked it up and it wouldn't power up at all. I checked for power on the brick and that seems ok. I do have a targus universal that I could test with but I'm not sure if it would be to much or not.

[selldoor]

Re: trouble IDing cap and best way to remove it?

Was it working before it was garaged?

Does the power supply output the correct voltage -are you sure its the one
for the monitor? Does it have a led on it and does it stay on?
Can you post straight on pictures of the front and back of your boards.

[alejandro22]

Re: trouble IDing cap and best way to remove it?

Good morning, I received this plate without the capacitor it brings and aside from the raised track, could you specify where the positive of the capacitor is connected to? since I don't have the schematic

[R_J]

Re: trouble IDing cap and best way to remove it?

Good morning, I received this plate without the capacitor it brings and aside from the raised track, could you specify where the positive of the capacitor is connected to? since I don't have the schematic

The clipped corners is the positive, if you look close near the white outline there is also a "+" mark