> 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.

This is purely conjecture, but it would fit with your symptoms. If you have a 
device that is connected to the standby power supply and doesn't behave 
properly, it may be trying to power up the rest of the system through the 
protection diodes of an IO pin.
It's a pretty common mistake in embedded systems, so it wouldn't be a 
surprise to find it in a PC peripheral card.
I would try removing as much as possible from the motherboard and see if 
the supply drops to 0V. If it does, add in cards until the problem returns.


Steve.



==========================================
Steve Baldwin                          Electronic Product Design
TLA Microsystems Ltd             Microcontroller Specialists
PO Box 15-680, New Lynn                http://www.tla.co.nz
Auckland, New Zealand                     ph  +64 9 820-2221
email: steve@tla.co.nz                      fax +64 9 820-1929
=========================================


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