My understanding of DC is that a circuit will need to be completed for current to flow. For AC that circuit can be with the Earth but with DC it needs to be with the correct terminal to provide the difference?
I don't think its a good situation. If the PC is broken and causing this I would be inclined to replace it. Also remember there are capictors within a PSU and they can shock you.
The -VE outputs are generated from a flyback winding wound on the main smoothing inductor. Which is simply run through a diode and filter circuit. Which is why they don't output much power. And why the voltage often sags on them.
richms: The 0v on an atx power supply is grounded to the case of it. If the 3.3 or whatever touches the case, it will shut down.
If one of the gutless -ve outlets touches the case, it will blow up that output because it doesnt seem to protect them. Dont ask how I know that ;)
Ok thanks. I am building a bench supply where a gutted atx psu case (used to contain the testing circuitry) will sit directly on top of another atx psu which feeds it. Was wondering if it would be better to insulate or shield the top psu case used for the testing circuitry from the bottom psu case used for supplying the power. I guess it is better to shield it to avoid the chance frying the supply psu. So if one of the dc lines in the case for the test circuit touch the case the supply psu will still work.
I am not modifying the bottom supply case.
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