My test was on a complete system, not just the supply. I think that 
the Vf of the various components in the PC may allow the caps to 
retain a rather high residual charge. A resistor would certainly 
fully discharge the caps. If the resistor doesn't work, there must be 
some leakage somewhere (WOL?). Low cost PC power supplies may not 
have drain resistors on the LV side, maybe not even the HV side.

> > Have you tried a small resistor on the 5V line?  100 ohm 1/2 W would
> > be a good start.
>
>No, I didn't think load was the problem.  I didn't make it clear in 
>my original post, I'm installing this in a PC *with the rest of the 
>PC still there*!  I'd
>have thought that the motherboard, two hard drives, floppy drive, 
>and three DVD writers would provide a load at least this big, 
>wouldn't they?  Or
>would the low voltage mean that they'd be effectively high 
>resistance?  (I have no idea what ICs "do" when the voltage falls 
>way below spec.)

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