I bought a 27 inch monitor from circuit city back around 2007 when they were having there going out of business sale for the bargain price of $400 dollars, crazy I could buy a small 4k TV or a 50+ inch 1080 lcd for that price these days! Anyways its a pretty solid monitor and I am not ready to let go of it yet, I want to use it as a display for my Radio Astronomy and SatCom SDR setup.
About two years ago the thing started randomly shutting off after running for a while, eventually it started shutting off within 15 minutes of turning it on and quickly shot down to turning off within the first minute while using it as the only unused display with an HDMI port to configure a RasPI. It sat for a while and then I took it apart six months ago to fix it and just sort of forgot about it until now.
Im not new to repairing flat screen displays, every TV, and some monitors I own were all repair jobs. I have successfully fixed mine and others displays of all different sizes and types (plasam, lcd), with all sorts of problems from bad caps to blown t boards, etc, etc. This monitor isn't an easy spot and replace issue though. From the behavior of the issues, it is obviously a problem in the power supply. By the way the issue slowly went from intermittent to quickly predictable and unusable I am going to say this is just a standard bad electrolytic cap issue. If you think it sounds like something else then please chime in and let me know where you think I should be looking.
Ok so if its just bad caps, why am I asking for advice?! Well this is the first time I have seen a device totally take a dump from bad PSU caps and none are leaking or even bulging enough that I can tell them from good caps. Here is the PSU board
https://www.dropbox.com/s/dvx1j51nckxtfx3/monPSU.jpg?dl=0https://www.dropbox.com/s/tr7shri69a0y220/monPSU2.jpg?dl=0So as you can see none of these caps look like they have issues and they are all 105c rated, but I guess they could still have dried out inside? They only tool I have to check ESR is one of these
over dressed cheap m328 based component tester. Im not even sure how many ohm's is actually a "bad" ESR, when it comes to electrolytic caps, I know I like to see under 2.5 ohms but if a cap measures 3 or 5 ohms is trash? Lastly this little tester does not do in circuit cap testing (I verified this before posting) so how the hell do I go about finding bad caps on this power supply? Is there a better method than soldering every single testing its ESR and then soldering it back in if it tests good?? Is there a quick ballpark esr pass/fail type of test I can do in circuit using a function gen and scope or something?
I really need to get this guy working, I can not afford to replace it at the moment, so my best cheapest quickest bet is bad caps, but they all look so good and have a hi temp rating it really has me questioning my cap theory on this one.