Question on fuse-blowing power supply

[cyclones]

Hi,
I'd like to learn more about electronics repair and I am currently looking at a power supply that just failed the other day. It is out of a Power Mac G4 MDD a.k.a mirror-door. The computer was freezing up for a little while and then turned off. I was able to locate a used PS for it (new are no longer available) and the computer works.

The PS immediately blows its fuse when plugged in (tried a new one). I checked for bulging caps but didn't find any, although they are the CapXon brand, which seem to always go bad. While looking over the board, I noticed what appear to be ballooned / bulging diodes. They are marked with DXXX as in D104, D107, etc. and they otherwise look like diodes. I've never seen anything like these. So far I counted 3, all in the same area.

I'm wondering if these are a clue to what's wrong with this PS.

Also, I'd like to know where I can learn more about testing and repairing electronics.

Thanks!!!

 

[(*steve*)]

Photos?

Learning electronics repair starting with a switch mode power supply is understandable (considering their ubiquity) but may be quite frustrating.

Having said that, I believe we've had someone get one working recently, so maybe I shouldn't be so pessimistic.

 

[cyclones]

Here's one I got the other day of the weird-looking diodes. I can try to get a better one on Monday.

This thread here at badcaps.net is talking about the exact same power supply and has some pictures of it. I don't have the burned spots on mine however.
http://www.badcaps.net/forum/showthread.php?t=7165

 

[Resqueline]

You mean the glossy white globular ceramic diode with a black band? That's a fairly common encapsulation, in particular for switching diodes.
You'll neeed to whip out a DMM and start measuring, beginning with the mains rectifier. Any pins shorted means you found a fault. Then you may move on to the main power switching transistor.