I received a non-working Poweredge 1950 that was dead. Being the technician I am I thought to repair the power supply myself. Couldn't find anything that lead me to a fix or a schematic, so I did what I usually do and that is slowly troubleshoot the stages using familiar switch mode power supply techniques. After maybe four hours total troubleshooting found a defective capacitor, which is usually the problem on switching power supplies.
After removing a mini PC board from the supply and replacing that one aluminum surface mount capacitor, that was completely dried out (the main failure on these) I reassembled the supply and put it back into the server, and there are not lights and it fires up.
I didn't get to take any pictures, so I'll try and describe where this part is for anyone who may want to repair these supplies themselves. The cap is located on a very small (pulse width modulator) circuit board that's located right next to the very large electrolytic capacitor. Once you open the unit you should be able to see the cap and it would have white glue that touches both and end of the large capacitor and the little cap itself on the mini PWM board. It's not an easy job to remove that board, but If a had to do it again, I would try to remove and replace it while the board is still mounted.
So any of these supplies that age should have this cap replaced.
Why take so much efforts in understanding the circuit schematics and trying to fix it when you can get a working used one for under $10 in ebay? It may not be a blown capacitor after all and I see no reason to spend a lot of time on trying to fix it when you can buy a working one for few bucks.
Cool good to know how simple it might be to fix them .To the other guy mentioning the 10$replacement i see your point but there is also shipping the cost of it and the time it takes.