G5 not powering up...

One day my G5 just didn's power up again.

No light, no chime, nothing...
Tried a new cable, changed the lithium battery, tried many power outlets, nothing...
Then I take it to the shop last week and they call me the day after to tell me that everything's fine...
Minimal charge 1/2 hour : $49.50...
Got it back today, plugged it 2 hours ago, nothing...
Called them, the technician doesn't understand ever and want it back... ????...
No idea before I spend more money...

Thank you,
Sam.

Power PC G5 Dual 2.5

Have you attempted to boot from your OS install DVD? Do you have the original system restore discs that came with the machine? If so pop in disc one and try to reboot from that. If no joy sounds like you have done a power supply and/or logic board.

Like I said there's no power at all...
But it did power up at the repair store... They said : everything is fine...

Well that is what happens at repair stores ~ they must use stronger of faster electricity. Did you see what, if anything they did, to get the machine to boot, such as target disk mode etc?