iMac switchmode PSU repair?

[a.d.a.m. baby]

The SMPSU in my 2005 iMac 20 inch just failed - no power getting to the motherboard.
This was the notorious model that suffered from the faulty electrolytics supplied by a few manufacturers. It was given to me a few years ago semi-working. I replaced all the electrolytics on the motherboard, only to discover later the bulging electros in the SMPSU. When they were replaced, it worked perfectly.
Anyway, now it's completely dead, so I suspect more than just a cap failure. Trouble is, these things are really tricky to test and fault find, and rather dangerous without an isolation transformer on the bench. I'm wondering if say an older TV technician or someone with experience like that might be able to fix it? Any suggestions?
There's none around on ebay.