The power on-off should harm it.
If the UPS is not big enough, it could make AC pulses with more then 220V
average.
Or it could, just before it went off, produce a nearly DC voltage at output.

"Bart³omiej Zarzycki" wrote in message
...
In my case power supplier was broken by starting PC+screen, then my UPS
was congested and automaticly turn off power for PC+screen (power in
walls was off for some reason). I have quite large screen (17")

Next I tray again to start PC+screeen form UPS, then them started for a
second and stop again. That situation was repeated several times and
after that I smell burning from back of casing of my PC (power supplier
or some part of power supplier was burning).

I repair them (except the complettely fried ones).
Most ATX suffer in the +5Vsb power generation.
The +5Vsb is a complete small SMPS. Very offen it brokes (high ESR cap)
and
it you have not a 7805 inside the PSU, you'll get probably a fried
motherboard,keyboard and some times PCI cards!.

The working period is not very long because of excessive heat produced
by
the stand by work.
When power is off for at least 30 minutes, and caps gets cold... Then
when
power is back on the +5Vsb will become up to +40Vsb (except the presense
of
7805).

I think that case we can exclude, because my supplier was broken by
several turning on and off in very shory period of time.


Even expensive brand models suffer from this issue.

to stabilize it after the +5Vsb SMPS