A few years ago I picked up an A500 for $2.50 at a thrift store. It didn't come with a power supply, but luckily (I thought) I had one for a C-128 that I had picked up for $4 at another thrift store earlier on.
I thought because the C128 and the A500 power supplies looked exactly the same, the would be interchangeable.
They weren't.
The red LED came on for a second....then something went *SNAP* inside the Amiga 500 and there was a bad odour of burning chips (I hate that smell)!
When I opened the A500 there was actually a piece missing from one of the chips that had burst!
Like any smart Amigan though, I kept the dead A500, knowing that even dead Amigas are useful for parts. Luckily, it has come in handy (the drive went into my A2000 a few years later).
Moral: always keep Amiga stuff, even if dead. They aren't making these anymore so spare parts are a finite resource.