I have a faulty A901 that we have had for 30yrs ish. It made a pop noise today and I have found the 56ohm resistor and a capacitor damaged. I guess more is gone on ours ie brushes and triac. But for you I guess you need the layout which I have in front of me. Best if I could snap a digital photo and send it on to you if you are still interested
Chris Easton
December 2006