Control Voltage...mods?

[swinginguitar]

I'm working on rehousing my FCB1010 (see previous thread). It's going well...pretty simple really.

The issue of the moment is I want to adapt what was expression pedals to either pots, or 1/4" jacks for expression pedal input. On another forum I saw where someone got them to work with 250K pots, but not very reliably...he was reporting random reboots (the FCB uses red LED/phototransistor/gradient to generate control voltage).

I connected a 250k pot, and it did work initially, but after a little while the pot got hot and started smoking (perhaps at low resistance settings there is too much current on the line since they were driving a LED/transistor?).

For reference, there are 2 black wires and a red wire. I measured 5v across red and black, and 2.5v across the 2 blacks.

Any ideas how I could adapt this to work with pot/pedal? Ultimately I"d like to be able to plug in a 10K expression pedal. Maybe I need current limiting resistors?

[swinginguitar]

BUMP....any experience or input?

Was browsing the Highly Liquid forum and saw a post that with their product they suggest a voltage follower buffer for pots > 10k

but i'm not sure if that applies here as I don't know what the FCB controller is expecting with control voltages.

[swinginguitar]

Another thought: if I can't get the onboard expr working - if i were to program a PIC to sample an expr pedal and convert to 0-127 midi hex, could i merge those values with the outgoing midi stream?

could i literally tack the extra wires on the midi out jack (with some protection diodes or resistors to prevent "backtalk")? sort of a midi thru situation?