44 | Oscillator Tuning Procedure
Oscillator Tuning Procedure
OSC 1 RANGE AND SCALE BOARD 1
The following procedure uses headphones for the oscillator tuning. An audio
amplification system can be used for this instead of the headphones.
NOTE: Periodically check the tuning of the A-440 tuner. If it is out of tune, simply use the
A-440 trimpot to adjust its tuning.
1. Set the A-440 switch to the ON position.
2. Set the Filter CUTOFF FREQUENCY control to the maximum position.
3. Set the Filter EMPHASIS control to the minimum position.
4. Set the LOUDNESS CONTOUR SUSTAIN LEVEL and DECAY TIME controls to their
maximum positions.
5. Depress the HIGHEST “A” KEY on the keyboard, and adjust the OSC 1 RANGE
trimpot for zero beats.
6. Depress the LOWEST “A” KEY on the keyboard, and adjust the OSC 1 SCALE
trimpot for zero beats.
7. Repeat steps 5 and 6 above until there are zero beats against the A-440 tone. Note
that this process may take several iterations.
8. Set the A-440 switch to the OFF position, but keep OSC 1 on.
OCT TRIM BOARD 1
1. Set the OSCILLATOR-1 RANGE rotary control to the 4’ position.
2. Set the OSCILLATOR-2 RANGE rotary control to the 4’ position.
3. Set the OSCILLATOR-2 VOLUME switch to the ON position.
4. Depress the HIGHEST “A” KEY on the keyboard and hold.
5. Tune OSCILLATOR-2 to OSCILLATOR-1 with zero beats.
6. Set the OSCILLATOR-1 RANGE rotary switch to the 16’ position.
7. Adjust the OCT Trim trimpot for zero beats.
8. Repeat as needed until both oscillators are in tune with each other at any setting of
the RANGE controls.
9. Return panel settings to the initial settings specifed on page 43.
10. Verify OSCILLATOR-1 RANGE and SCALE by verifying the HIGHEST “A” KEY and
LOWEST “A” KEY are still in tune. If not, repeat OSC 1 RANGE AND SCALE
BOARD 1 tuning procedure from above then repeat Steps 1-4 of OCT TRIM
BOARD 1 procedure. Repeat both procedures until no more trimpot adjustments
are needed. Do this before moving onto OSC 2.
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