17" iMac G5 w/ Ambient sensor won't start up

Hi Everyone...Have this iMac and am going through the troubleshooting. It has the internal power switch/button but, oddly, not the PMMU reset switch that the guide says SHOULD be just below it.

Anyway, I get LED 1 indicating that trickle voltage is there and, supposedly, the power supply is okay.

When I press the internal startup button, I hear a tiny noise, LED 2 tries to light but no startup.

Same result by shorting the two pins on the main power button. (with machine opened up)

Following Apple's troubleshooting, the remedy is to replace the motherboard. I think not.

I removed the power supply and then re-installed it and I have to think that it is the power supply. It seems like it is trying to start but just isn't getting enough out of the PS to get going.

The serial number is not within the range of the recall...

Any suggestions? I hate to spend $200 on a PS only to find that it is, in fact, a toasted motherboard.

Thanks for looking and helping...

Regards,

joe