Vintage Simmons Drums (UK) Users Group

God this thing's infuriating.
Ok bought the schematics - with fantastic graph paper squares obscuring the important details - and started having a hunt around

I have restored 15v to the board but obviously that hasn't made a blind bit of difference as all triggering logic seems to be tied to 5V.

Right I've just been triggering it using the demo on a yamaha drum machine.  Still only getting the bass drum trigger light coming on.  

Checked IC64 with my scope.  Bass drum throwing out logic changes on 13 and 2 for the bass drum.  Had a look at the Env on IC64 for all the "other" channels and nada - not checked the other mux ICs yet but I'm guessing it'll be similar.

Could someone advise where to look next in diagnosing this?

Cheers
Stevie