[Amps] Alpha "TUNE" Meter Function Calibration

[Paul Christensen]

Anyone know the procedure for calibrating Alpha's "TUNE" LED meter function on the 86, 89, or 87A?  Three pots are used on the logic control board to establish calibration.  One sets the quiescent bias onto a comparitor for mid-scale, while the other two establish gain for plate and cathode sampling.  Unfortunately, no info in the owner's manual on the calibration procedure and the adjustments interact with one another.  Tnx!

Paul, W9AC