I was given an iMac G3 400 DV but it wouldn't turn on. I can hear the monitor click then nothing.
I downloaded the Apple Source iMac guide and went through the "No Power" troubleshooting section.
First I replaced the battery, the previous one was dead completely.
I tested the logic board for trickle power (J9) and it showed +5V correctly.
I then tested the DCO power (C10) with power cord plugged in and it showed -1.3V correctly.
I couldn't test the down converter board (J7) because it said to test with power on and I can't get the power to stay on.
I then tested the fuse (F901) and it was good too.

I reset the PMU as described in the guide.

How do I know if it's the Power/Analog/Video board or the Down Converter board?