My most recently acquired A500 does funny things.
I've plugged in a modified floppy drive, booted flimbos quest... then realised I needed a keyboard.
SO, powered off, booted up, went to press F1, keyboard didn't work, then I realised the power light had gone off.
So, tried again, this time while booting I watched the lights.
It appeared to be going fine, till both lights went out, then the power light seemed to become the floppy activity light.... ah?
Tried booting again, except this time both lights went off, while the activity light on the floppy drive itself remained on, but nothing booted... unplugged the keyboard, and it booted fine?