Have you considered having yours repaired? JJ at the Amiga Repair Center in France does a great job. Send your motherboard for a free estimate. You can contact them via the web at:
http://www.amigacenter.com/Homer.htmlI sent them my 4000 motherboard in 2006. They did a wonderful job of fixing it up, putting in a replacement battery and bringing my machine back to life.
Might be your cheapest option for fixing your machine.
