Vintage Simmons Drums (UK) Users Group

Hi everyone  

My Simmons SDX has this symptom recently!!!!
It seems  4  voices wont sound and  weirdest thing... The voices that do work cant be replaced  even if deleted and replaced 
Reloading a new  disk sound  or sample sound  into an existing instrument does nt change the sound even though it loads   ..Also making the slot blank and and reloading a fresh sound does nt work either  .I m baffled  any advice or help would be great .
Everything else functions normaly