Oberheim OB-Mx calibration ROM and instructions

via Aaron on AH:

"Courtesy Tom Virostek.

See here: http://users.ece.gatech.edu/~lanterma/obmx

The calibration procedure is pretty complex and requires a scope (and preferably the voice board extender card that lets you get to the board while the unit is on). The OB-Mx uses some digital pots with built-in nonvolatile memory. I had always assumed that these were recalibrated upon booting up the OB-Mx, but it turns out they are set in this calibration procedure. I suspect that a lot of errant voice boards that are out there just need recalibrated. Maybe some of them were sloppily calibrated to begin with - who knows.

- Aaron

P.S. One caveat is that Lynx Crowe told me he recalled there being some runs of voice boards where Gibson used the wrong sort of capacitors in the oscillator section, resulting in boards that went out of wack as the temperature changed. He couldn't recall exactly what or where."