PSU repair, found strange cap, need guidance

[Enginuitor]

Long story short, I set up the back terminal strip according to the strapping diagram for local sensing and control.
It miraculously worked!...
For a short period of time.

Everything was working fine, so to test the current output I put a small wire across the output. I started easing the current up, and it did fine up to about 3 amps, then suddenly the needles dropped to zero. I think I may have heard a small click, but I'm not sure. This is a 10-amp power supply -- What happened??


Now it's in a truly wierd state. When I turn it on, the voltage slowly rises, charging the output capacitor, until it hits the OVP cutoff point (set by a small potentiometer; I have it at about 46 volts) at which point the relay shuts down the output stage. This happens regardless of the voltage settings, though a higher setting seems to make it happen more quickly. Obviously the system is no longer regulating properly.

Currently I am running the manufacturer's calibration procedure to see if that might catch the problem.

By the way, there is a full schematic in the pdf I linked to.
Any suggestions?

 

[Enginuitor]

Here is the schematic for those who don't want to deal with the PDF:
Click here to enlarge

 

[ante1]

Greg,

It looks like U9 / U1 is a switching pre-regulator, the setup maintains the voltagedrop over Q9 to minimize the heat. Do this part work allright? C5 has an unusual symbol but I think you can replace it with a standard but low ESR cap, if it

 

[Enginuitor]

Thanks for all your help. Since we're past the capacitor issue, let's move this discussion into my other thread (Electronics Chit-Chat -> "Help with power supply repair") so we don't have to jump back and forth.