This page includes the downloadable binary file for Drumulator OS3.0 and also has my crude schematic for how to add the minimal circuitry needed to get MIDI into the Drumulator (sorry for the lame scan, but it should be readable). 

 

This mod is based upon what I was able to copy from a Drumulator that had a factory-fitted MIDI retrofit, so I know it works.  Here's a bit of proof:

 

 

 

After you download the binary OS file, you'll need an EPROM burner to load the file into a 2764 EPROM.  I'd advise burning a separate 2764 for this OS instead of overwriting your present Drumulator's OS chip, just for debugging during the install and having a backup.

 

Sorry it's not more fully featured, but hopefully you can DIY your way to the solution.  I'm happy to try and answer questions via email.

 

Thanks!

 

Two important items:

 

1. I am not responsible for any damage you do to yourself or your Drumulator by providing this info.  It's free for your use because there don't seem to be any other easily accessible resources to this mod (and the dynamics you can get from using external MIDI controllers really expand the Drumulator's use, imo).

 

2. I don't take on tech work because for me this is a hobby and I don't want to take on the responsibility or time burden of doing professional-grade work on other folks' equipment.