I made some smoke on A500...

[gertsy]

It's a standard part. Someone else will know exactly what it is.

Here is what I think it is:
http://www.jaycar.com.au/productResults.asp?whichpage=1&pagesize=10&keywords=choke&form=KEYWORD

Filter or a choke.

Yep it's a ferrite choke, which is usually paired with a voltage regulator.  This was a common part to blow on a ZX Spectrum if the polarity of the pwr supply was incorrect.... ( o:  That and the voltage regulator. It is more than likely that this wasn't the only thing to go on the board. I wish it wasnt the case and I hope I'm wrong, but I don't think you will have much chance of finding all that smoke and getting it back in place.
Look at it as a learning experience and a worse case way of freeing up lots of spare custom chips and a processor.

Good luck.

[gertsy]

Oh, I guess you are right about that. The case was pretty yellowed anyway and it was Rev.5 mobo, so maybe I make this my spare parts machine, at least it has working keyboard and a floppy drive to make other Amigas live

Dare I say you can fix a yellowing case...http://retr0bright.wikispaces.com/

[gertsy]

I hate chemistry! With my luck I end up being blinded or something... But it would be really cool to test and see the results personally. Have you tried?

On MBS topic; yes lots of it escaped this computer that day! Without in depth knowledge of electronics I think I'll take it as a lesson to myself.

On retrobright, no I haven't but if you search this forum you will find a few posts that settle on how to get consistent results.  Also straight peroxide can be difficult to get in some countries, like Australia.  )o: