TUNING SCALE/RANGE CALIBRATION
WARNING
This procedure will expose the user to hazardous voltages. Proceed with caution. If you are
in any way uncomfortable with this procedure, then take the unit to a qualified repair shop. I
am providing this for information only and the user assumes all risks.
This procedure requires a strobe tuner or a frequency counter.
You can calibrate the oscillator with or without the rear cover intact. There are access holes
for the trimpots, but not all of them. It is also possible that you have a older Minimoog with a
newer oscillator board, and only the access holes for the older oscillator board.
These instructions are laid out for calibration without the rear cover, so you should keep the
Minimoog in a stable environment, IE away from drafts because abrupt changes in
temperature will affect your calibration.
For instruction on removing the rear cover, refer to the Power Supply
CALIBRATION SECTION
1)
Apply power to the Minimoog and allow a 30 minute warmup period.
2)
Connect the tuner or counter to the HIGH MAIN OUTPUT jack.
There are two large boards as you face the rear of the Minimoog. The board
on the right is the oscillator board. The board on the left is the Filter
board.
A440
3)
Observe the Filter board. The trimpot on the bottom left hand side is the A440 trimpot.
Turn on the A440 switch on the front panel and adjust this trimpot for 440hz.
4)
Turn off the A440 switch on the front panel.
At this point, we are ready to calibrate the Oscillators. There were three versions of the
oscillator boards.
The first version was originally installed in Minimoogs up to approximately serial #1300 and
were entirely discrete, but is mentioned nowhere in the service manual. I do not have
schematics for it, and I do not know what it looks like. I cannot verify if this calibration will
apply to this oscillator board version. It is pretty likely that most of these boards may have
already been upgraded to newer versions. If you have a Minimoog that is under #1300 and
you are not sure which board you have, you will need schematics and a qualified repair
shop to tell you which board it is.
The second version is more common and was installed in Minimoogs below serial #10175,
beyond that the third version (the temperature stabilized board) was installed in Minimoogs
serial #10175 and up. Older Minimoogs may have their original boards replaced with the
third version.
