Future Retro 777 Tuning Procedure User Manual
Future retro 777 tuning procedure
Future Retro 777 Tuning Procedure
The 777 contains five internal trimmers. One to calibrate the V/Oct DAC, and four that
are used to set the scaling and initial frequency for the oscillators. These trimmers are
calibrated at the factory, but may need to be adjusted over time.
You will need to remove the 777’s front panel to access these internal trimmers.
turn the unit’s power off while removing and reinstalling the unit’s front panel.
This procedure includes removing the front panel knobs, by gently pulling them off, and
removing the 7 hex nuts around the toggle switches. You will also need to remove the
four black screws at the bottom front of the unit, as well as the four black screws on the
rear of the unit. Once this is done the front panel can be removed by carefully pulling the
chassis panel up.
Turn the unit on and let it warm up for approximately 20 minutes before attempting to
retune the oscillators.
First you need to make sure the DAC is calibrated to produce 1 V/Oct. Use a short ¼”
cable to connect the CV out of the 777 to a digital voltmeter (shied connects to the black
lead, tip connects to the red lead of your voltmeter).
Play C1 in the 777, and check the CV out voltage reading. Then play C6 in
the 777 and adjust the blue trimmer (located on the right-hand side of the switch board)
so that note C6 produces a voltage which is exactly +5v higher than note C1.Go back and
forth between playing C1 and C6 a couple times to make sure the difference is +5v
between the two. Once this is done, you’re ready to tune the oscillators.
There are several methods you can use to tune the 777’s oscillators. The best method will
be to use an oscilloscope or music tuner. If you don’t have access to these tools you can
attempt to tune the instrument by ear, or compare the oscillator tuning to another
If you are using an oscilloscope, locate the big blue colored capacitor (by the power
switch) and connect the ground lead of your probe to this capacitor’s lead nearest the
edge of the board. You can connect the main lead of your probe to the left-most pin of the
prefilter gain control pot. This allows you to monitor the oscillator’s raw waveforms
simply by turning their level up.
If you are using a music tuner, simply connect the output of the 777 into the tuner.
To start with, set all the front panel controls to their left most position.
Set oscillator A and B frequency controls to their mid position, turn the filter’s cutoff
control to maximum, and make sure the volume control is up if you wish to monitor the
sound as you are tuning.