[CUBE] no power to cube -- logic board?

[Frank French]

Mike, 
No magic cure but there hasn't been a rash of dead logic boards that I've
heard off. There was a QuickTime video available from one of the upgrade
companies that explained how to change the CPU. I'm a great believer in
taking things apart and putting them back together. If you haven't already
done that of course.

I'd take it down to bare bones, removing the RAM, video card, DC power card,
Hard Drive and CPU. Then remove the battery from the logic board and take a
break of about ten minutes, that resets the logic board.  Now if you have
the speakers that came with the cube my next step would be the CPU, DC card
and one stick of ram then battery. No video card, no drives. Chassis out of
case, then I'd put just see if it would start. If it won't start off the
chassis button do you have anything else, Apple LCD display or an older G3/4
USB keyboard with power button. (Not sure if they work on the cube but they
do on some G4's)  

After that it's probably component swap time but it doesn't sound as if
you're set up for that... cube chassis and motherboards do come up on ebay,
and there was a company in the UK selling just motherboards for about half
the $800.00 price. Good luck.

Regards

Frank