I just checked a system with an Antec power supply. It drops to 25 mV 
within a few seconds and stays there.  The 12V drops right down to zero.

Have you tried a small resistor on the 5V line?  100 ohm 1/2 W would 
be a good start.


At 11:11 AM 11/13/2006, you wrote:
>I tried building a device into a PC which was powered from the +5V 
>line on one of the disk drive power connectors, and found that it was very
>unreliable in starting up - more often than not it didn't!
>
>So I put a meter on the connector and found that when the PSU has 
>mains connected, but is turned off, there was 1.8V on the 5V line, so powering
>the PC down and up does not power the device I mentioned down 
>properly.  From cold it seems to work if you connect the power lead 
>and then press
>the power-button within a couple of seconds - more than that and it 
>locks up the device.
>
>I tried another PSU and that was showing 0.8V and had the same 
>problem.  I know there is a separate 5V Standby supply, but I would 
>have thought
>that the main 5V should drop to zero when power is off, shouldn't it?
>
>Has anyone else encountered this?  Am I likely to find a PSU that 
>does behave "properly"?
>
>If not I'll have to use the +12V and put my own 5V regulator 
>in-line, which will be annoying but will solve it (the +12V line 
>does drop to zero).
>
>Cheers,
>
>
>Howard Winter
>St.Albans, England
>
>
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