LG M227WDP 21.5" - Caps all seem fine

[JoeyJoe]

Hi,

I've fixed monitors previously by identifying and replacing bad caps, but this one has me baffled.

The monitor is a LG M227WDP 21.5" TV / Monitor 1080p etc. I bought it broken off eBay with the fault of it turning on for a few seconds then the screen goes blank.

I connected it up today, and the screen was working fine for around 10 seconds with a display and then the screen went off. I thought I saw smoke come out of the top, but I can't find any evidence of burnt components inside at all.

I've stripped it down. and I can't see any burnt components on the power board. The caps all look fine. I tested them by de-soldering and putting on a voltmeter to test them charging on the ohm setting and they seem fine.

Here is an identical image to the powerboard I have.

Does anyone know what I could try next to identify the problem?

[tom66]

Re: LG M227WDP 21.5" - Caps all seem fine

This is probably a bulb in the panel that is arcing or bad.
Follow retiredcaps 2 seconds to black guide.
https://www.badcaps.net/forum/showthread.php?t=10419

[JoeyJoe]

Re: LG M227WDP 21.5" - Caps all seem fine

This is probably a bulb in the panel that is arcing or bad.
Follow retiredcaps 2 seconds to black guide.
https://www.badcaps.net/forum/showthread.php?t=10419

Ah
Now that you mentioned it, there's some buzzing sound coming from the back of the screen. Is this something that you can fix without replacement?

[mariushm]

Re: LG M227WDP 21.5" - Caps all seem fine

Buzzing may indicate just that the wire going to the bulb isn't making perfect contact.

Before making any decision, carefully check the ends of the lamps by removing the silicon boots at the ends and inspect the ends. In some cases simply soldering the wire fixes the issue.

[budm]

Re: LG M227WDP 21.5" - Caps all seem fine

If you have AM radio, it will pick up arcing noise.

[tibimakai]

Re: LG M227WDP 21.5" - Caps all seem fine

I have a pretty similar one and I hear that buzzing also, I have picture, but the backlight is very dim. I had to replace the OZ chip though.
I couldn't find those two 8 pin FETs in that package size, only SMD package.
Not sure though if those are good or bad.
It was a pain to take the screen apart. In the process I have busted a tube in there, which I had to replace.

[JoeyJoe]

Re: LG M227WDP 21.5" - Caps all seem fine

Thanks for all your inputs!

I have now got the monitor in bits again, with the screen on my living room floor. I've manage to detach the metal bezel that surrounds the screen. I can see the ends of the lamps with the 2 wires going into each, but not sure how to access them. I could pull the LCD from the backing, but something tells me this is the wrong move! Is there a guide for this sort of thing?

[JoeyJoe]

Re: LG M227WDP 21.5" - Caps all seem fine

Hi again!

I'm not sure what I've done but it suddenly started working.

I can't hear any buzzing, and I have tried to wiggle the leads a bit, but seems to be OK.

Any ideas?

EDIT: Spoke too soon. Turned off again, although has managed to stay on for such a long time this time!

2nd Edit: While trying to make a quick video of the screens behavior, I start hearing a clicking sound coming from the power board. The transformer that powers the tubes then started to smoke and burn, while the screen was still lit. I assume now that I will need a replacement transformer to fix? Or could this be a symptom of another problem?