I suppose that it has to do with the discharging of the capacitors inside
the switching power supply modules used in the A-100PSU3.

Best wishes
Dieter Doepfer

> Measured the output voltages from the +12, 5 and -12 spades on
> the bus boards. All within .1v, and no sign of any spike at power
> on/off. So looking good I guess.
>
> Weirdly, I noticed that in my other case with factory-installed
> PSU3, the LEDs will flash at power off/on when it hasn't been
> turned on in a while, but if I turn on/off again a few times they
> stop flashing. So who knows As long as my case is safe. Thanks
> again for help!