Acer AL1715sm monitor repair

[mrhoneybadger]

Hi all,

I've started watching Dave's EEVblog recently and got very encouraged about trying to fix some of the broken things around, even though I know next to nothing about electronics.

This monitor is an Acer AL1715sm and it's 5+ years old and when it's plugged into power, the power (and the power LED) keeps turning on and off about every 2 seconds. I had a look at the board to check if any of the capacitors were bulgy or leaking, but it doesn't seem that way (attached picture 1). The only thing I can think of that could be wrong is that the transformer has some dark yellow liquid stuck on top of it (attached picture 2), but I'm not even sure it means anything.

I tried to google answers for both the symptoms and the yellow goo, as well as have a look at the service manual, but unfortunately understanding most of it was beyond me at this stage. I hope someone here might have some tips what to look for, I'm not sure what else to do at the moment.

The transformer is marked on the board under T901, if this helps.

I could not attach the service manual as the file size was too large, however it can be found here: http://www.go-gddq.com/upload/2009_08/09081816054725.pdf

Thanks very much.

[thm_w]

The yellow looks like normal varnish type coating, they may have dipped the transformer at some point.
http://www.temcoindustrialpower.com/product_selection.html?p=primary_vs_secondary_coil_varnish

Darkened board indicates reasonable heating. Entirely possible the capacitors have dried out even if they don't look bulged.

If you do not have an LCR/ESR meter to check them, you will have to (very carefully) measure the voltage rails. There should be some videos where Dave or others have done this to locate a bad cap.
Look for anything clearly out of range or oscillating, etc.

[mrhoneybadger]

Thanks for the reply, thm_w.

To be honest, I don't have any tools yet (not even a soldering iron), so the point of my post was also to figure out what to get to fix the screen :-). I'll follow your advice and get a multimeter to try to measure the voltage rails (though I'm not too comfortable with this as I have no idea what safety precautions to take, so I'll have to look into it more first), or desolder one leg of the capacitors and measure their capacitance with the multimeter (so far I've picked one that can also measure capacitance: http://www.ebay.com/itm/Electrical-LCD-Digital-Multimeter-Voltmeter-Ohmmeter-Ammeter-Capacitance-Tester-/131460539658?pt=LH_DefaultDomain_0&hash=item1e9ba8a50a).

From what I've found out so far (also thanks to you, for pointing me in that direction), it will probably be one or more of the capacitors near what looks like a diode block on the lower part of picture 1. I doubt that the big capacitor that gets AC fed to it at the beginning of this circuit is faulty, due to the nature of the symptoms and other peoples' experience.

By the way, soldering iron :-) : http://www.ebay.com/itm/AC-220V-240V-60W-Electric-Soldering-Iron-Welding-Tool-EU-Plug-Yellow-New-/281566218853?pt=LH_DefaultDomain_15&hash=item418ea78a65
Yeah it's really cheap, but hopefully it'll get me by in a pinch when I'm soldering once per 1-2 years.

Thanks again.

[wraper]

Likely something wrong on the primary side of the SMPS. Try to change a small capacitor near to the PWM IC.