Problems after replacing failed PSU for Abit KV7

I recently had a PSU fail and am having problems getting the replacement unit I bought to work. I was hoping someone might have some suggestions for me. Any help is greatly appreciated!

My motherboard is an Abit KV7 (socket A). I purchased a Thermaltake TR2 RX 550W PSU to replace the failed unit (older Antec 350W). When I power-up the system, the lights come on and the fans turn but I get no video output or any of the usual beeps that I get when the mobo powers up (also no error beeps). It's as if the CPU is not running

Is there any reason why the Thermaltake PSU should not work with my KV7? The new PSU has a 24 pin connector but it was my understanding that this will work fine with a 20 pin mobo. Can someone confirm this? Also, the new PSU does not have the 3 pin fan signal connector that the original unit did but I assume that this should not cause the problems I am having.

I've tried a different video card with no luck (didn't expect it to) and am concerned that the PSU failure took the mobo or CPU with it. The old unit failed after powering down. The system was working fine when shut down but would not power up again -- no lights, no fans, no beeps (also no "bad" sounds -- pops, cracks, sizzles, etc.).

Is there anything I am overlooking? Again any thoughts/ideas/suggestions appreciated!

Thanks.