Puzzling Power Issue

[jim11662418]

I have a 5150 PC and a 5170 AT, both with stock, original power supplies. Both were on this morning when I left the house for a walk.
Both were off when I returned about an hour later even though both power switches were still in the "on" position. Both LCD monitors
were in "standby". I turned the power switches "off" then "on" and both computers started normally. Any ideas what may have happened?

 

[mR_Slug]

As it affected both PSU's the only thing I can think of would be over-voltage protection. They also shutdown if there is a direct short on the output. So if they were connected together some way and somehow 5V were accidentally shorted to GND, you would get a similar situation.

 

[Stone]

A brief power failure can shut down the machines and without enough lag time they will not restart automatically.

Do you have any digital clocks that need to be reset? That would be a dead giveaway.