Monitor dead?

Sounds like the monitor...
.....and that the line output stage is 'kaputt', this provides
horozontal scanning and various other voltages inc. the 10KV or so for
the CRT's final anode.

What happens is the power supply starts up... any heavy load or shorts
will cause it to 'trip', since in the trip condition there are no or
very little secondary voltages the whole thing start's up again as if
it has just been switched on.... and it goes on and on.

Only one way to confirm is to try another monitor... or try it on
another unit.

If it's a simple component then the cost is usually reasonable, such
as a diode , capacitor or transistor.... but it's anybody's guess
should it be the line flyback transformer some are cheap some are
not...

Davy