I have 3 u2311h monitors in an Eyefinity setup. For aesthetic purposes, I do not want to replace the faulty one with a newer u2312hm. The problem with the faulty one is as follows:
For the past few weeks, when I turn it on, it flashes the screen (ps3, Windows 7, whatever is connected) for a few seconds then turns black. Turning it off and on a few times and if I'm lucky, it sticks and works properly. Recently however, it never stayed on and always went black. I have read online that it's a sign of faulty capacitors.
I have opened the monitor and there are two PCBs. One for the main power connector and one for the VGA, DVI, USB etc. I can't for the life of my identify any capacitors that look faulty based on "spot a faulty cap" guides on the internet. None of them look bloated :/
I am fairly proficient with a soldering iron so I am confident I can replace any parts of the board. Am I going along the right tracks here or is this problem nothing to do with the capacitors? Also if it is to do with the caps, which ones do I replace? The ones on the power board, or the other board? Or both?
Edit: I have replaced all the small caps but unfortunately the same problem was still there. I didn't replace the massive cap on the board as an oversight. I have just ordered a new replacement powerboard anyway so that should do the trick.
Best Answer
It has been my experience that the problem symptom you have seen is related to bad capacitors in the power supply board. I've replaced such capacitors in almost a dozen different monitors that had the same symptom and ended up working like new after repair. There have also been a couple of monitors where capacitor replacement did not fix the faulty behavior of the unit.
Some hints to think about before you dig into things and rip everything apart.
Label all wire and cable connections before taking anything apart so you can easily get it back together again in the correct manner. There is usually a lag between opening the unit and when you are ready to snap it all back together again that could be even 10 to 12 days. It is easy to forget how it all connected.
Make up a detailed list of every capacitor on the board as you work including the location where each was soldered in.
Most monitor power supply boards are cheap cheap one sided boards. It is very easy to damage the board copper pads and lands when removing the old capacitors. Make sure to use careful techniques when unsoldering including use of solder wick. Make sure the leads are free before trying to pull out the capacitor or you risk ripping the pads right off the board.
Some capacitors may be mounted on their side and glued down to the board with a hard white compound. Best first trick with those is to slit open the outer plastic wrap on the capacitor with a razor knife so that the capacitor body can move around while you free the leads.
Measure all the capacitors accurately. Replacements come in many
sizes and often size a replacement that is slightly larger may not
fit correctly once the monitor chassis enclosure is put back
together. Measure the length of the body, its diameter and the lead spacing. Replacements are often specified in metric mm dimensions.
When looking for replacements make sure to observe the temperature rating and voltage ratings. For instance do not replace caps that were 105C rated with 85C caps. The life time of repair will be significantly reduced if you try to scrimp on the replacements.
Select replacements from respectable vendors such as Panasonic and Nichicon. Stay away from unrecognizable brands like the types you are removing.
Note that the capacitors in these switching power supplies generally need to be high quality types with very low ESR and good Ripple Current ratings. Replacing them with cheaper garden variety capacitors is inviting early failure after the repair; if they work at all.
When reinstalling the capacitors make sure to observe the polarity markings and get the minus and plus sides aligned correctly.
I have found www.mouser.com to be a good source for replacement capacitors.
Good luck with your repair.