When you are told you need a new logic board please let me take a look at your iMac G5 1st or 2nd generation. It could be the power supply. I restored them. When your logic board need recapping, I do that too. Please don't sell your machine for pennies before you allow me to take a look.
You don't sell your Benz or Lexus when you only need a new alternator, or battery in it!
PSU $75.00
Logic Board $150.00
Please call Gene 917-885-0707
or email: gngene@gmail.com