This is a short synopsis of the FatMan calibration procedure.
This procedure does not include trouble shooting hints and assumes a known working FatMan. These notes would be appropriate for recalibration only and assumes that you've done it before with the manual.
Connect and configure MIDI on the FatMan and another synth so that when you play notes on the FatMan the other synth plays too.
Note: It is important that steps 1 through 7 be done as accurately as possible. These steps adjust the DAC for optimum linearity. If this is off, the FatMan will not track well with other instruments. The word "unison" means that there is no beat between the FatMan and the instrument you are tuning it to. I strongly recommend using a digital synth since they are extremely octave accurate.
I advise that either the "Lee Diode" modification be done OR replace the 555 timer ICs with ICM7555 CMOS 555 timers. Doing so before performing the above procedure will allow making the VCO1/VCO2 tracking adjustment (steps 9 and 10) more accurate. Either of these mods allow the two VCOs to run much closer together in frequency before they will soft sync (lock together). I have two FatMan synths, one with the Lee Diode mod, the other has ICM7555 ICs. I can calibrate the VCOs closer than 0.1 Hz on both. My preference is using the ICM7555.