after a LOT of troubleshooting, it would seem that the problem was a faulty electrolytic capacitor (component C217 on the AM board schematics). I will get a replacement and confirm if it is a success.
Hi - I replaced C216 and C217 but still have the relay close a few seconds after powering up. The rest of the keyboard functions fine but no sound through speaker or headphones. Any other tips? Brendan