Attempting repair of H240AS-00

[hackdog]

A friend of mine has had several Dell power supplies fail in a school and asked if I could figure out the cause. They are model H240AS-00 and they all died from the same catastrophic breakdown of snubber cap C52 as described in threads here, here and here. Parts visibly damaged are Q51, C52, R25, R55 and D53. The fuse and rectifier diodes still measure OK.

I'd like to check if these PSUs can be brought to life by temporarily replacing those 5 parts with stuff from my junk box:

1. can I substitute a 1 nF, 2 kV cap for C52 (680 pF)? Not sure how critical the capacitance is here.
2. what is the orientation of D53: stripe towards the edge of the PCB or towards the center?
3. can I use a 1N4148 for D53?

[hackdog]

Re: Attempting repair of H240AS-00

For posterity, here is the outcome. By comparison with another still working supply, it turned out that the cathode of D53 is near the center. It's a moot point though, as the driver IC and some other bits on the upright PCB had exploded. So these supplies are definitely not repairable after that snubber cap has gone. Pity.