I have a USB device which I want to keep powered when the computer is turned off (not standby or hibernate but off) - but still plugged into the mains. i.e. the PSU is still 'live' but the fans are not running and I beleive only standby power (VSB) at 5V is supplied to the purple wire on the ATX power connector to the motherboard.
Can I wire the red and black wires from a USB cable directly into the power connector (to purple 5v VSB and black wire ground) and expected my USB device to receive 5v power to keep it running ?
Is it dependant on the powerdraw of the device ?
I haven't put a meter on the ATX purple wire yet but would appreciate some feed back if what I'm thinking of is feasable.