Power Tolerance



Hi

Anyone know what tolerances should be expected from a PC's power supply? ie
12v +/- ? 5v +/-? etc

I have a problem with external USB hard drive devices loosing connection,
After some time checking drivers, power settings BIOS etc etc the only 2
things I can see is 1 the main board is defective or a problem with the
power supply??

Any ideas?

:o)


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