Optigan

Attached to each amplifier is a little trimpot for adjusting the chord/keyboard volumes. On most Optigans, these trimpots can be accessed by the little holes on the back of the unit. If you still can’t get much sound out of an amp, or the sound is particularly distorted, the the amp has gone bad and [...]

Crosstalk! Learn to live with it! If you don’t have the test discs, the easiest way to hear the crosstalk is by pressing the top most key on the keyboard. Crosstalk changes with the weather, basically- the light detector is very sensitive to temperature and atmospheric changes. The result is that adjacent tracks on the [...]

Here’s a freebie from the Service Manual - it’s instructions on how to modify the outputs on your Optigan to be more suitable for recording and amplifying.
Optigan Audio-Output Mod [pdf]