Archive of the former Yahoo!Groups mailing list: Vintage Simmons Drums (UK) Users Group

I believe the 8051 is MROM.  There is (was) a programmable version - the 8751 - so you could program the code into one of those.  Your problem will be extracting the Simmons code from an 8051 - possible but difficult.

Are you 100% sure the 8051 is dead.  It needs pulses from IC2 to work correctly.  Check pin 12 with a scope and make sure it's getting pulses from IC2 pin 3 - otherwise it will play dead.  Also worth checking pins 18 & 19 to see if the clock is running - crystals and ceramic caps can go bad.

Before you go much further, check the supply - there should be 5v and +/-6v.  I've seen the regulators fail, giving out raw +/-12v.  This will cause a lot of damage - probably toasting the CEM3394s and other stuff - and cause enough damage to upset IC2 and freeze the 8051.  The cost of replacing three blown 3394s would be similar to the cost of a working SDS1000.

 

Steve