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.

 

[lolo799]

I tried two working floppy drives, one from a 9500, the other from an LCIII, same behaviour.
I haven't recapped anything, but I think a previous owner did.
I see corrosion on the adb port shell and on some components leg.

 

[Boctor]

It could always be the lighting in the photos themselves, but those joints look too green and dull for this to have ever been recapped or washed.