LC reboots when a floppy disk is inserted

[lolo799]

In trying to make an old software work, I bought a LC with a dead power supply.
I managed to power it up with an ATX power supply and some rewiring, only providing +5 and +12 volts, if that matters.
As the title says, as soon as a floppy is fully inserted, the screen gets scrambled and the machine gets in a reboot loop.
Anyone has any ideas what could cause this?

 

[bibilit]

A short in the floppy drive unit ?

Have you replaced capacitors ? LC series are prone to nasty leaks.in these areas.