I’ve recently bought a Tama TS305 drum-expander which is a great sounding machine but unfortunately totally lacking of midi control making it difficult to be integrated in a flexible way into a studio setup.
So, what I had to do was to modify the TS305 and add a midi-to-trigger interface to it. Since the machine only has 6 channels and no velocity sensitive trigger inputs, I decided I wouldn’t need a fancy trigger interface and developed my own PIC16F628A based, low cost 10 channel midi to trigger interface. The complete project with schematics and firmware can be found here.
Once the module was finished and tested, I started modifying the TS305. In order to be able to trigger the drumsounds, I added an second input to the external input jacks in such way that the module will be triggered from the internal midi-trigger interface when no external trigger jack plug is inserted.
To achieve this behavior, I have unsoldered each individual external trigger jack, bent jack pin C flat, wired input C to the trigger module and soldered it back in again (in such way that pin C is now no more connected to the PCB).
Here a snapshot of the trigger circuit:
I also found some good instructions on how to make the trigger modification at cykong.com and Circuitbenders.co.uk has made some more modifications to the voice boards in order to alter the sound of the machine.
Here some pictures of the modification: