The oscillators of the Polivoks incorporate special scheme for the thermal stabilization, which allows to hold pitch and scale during the temperature changes. IC of the exponential converter is warming up to the temperature of 50 deg C, which is holding stable precisely. Therefore if your Polivoks doesn't hold the pitch and scale, you must first tune the scheme for thermal stability.
1. Leave the synth in normal conditions for at least 2 hrs.
2. Take the synth out from the low part of its case and set it vertically on one of the synth's sides.
3. If the synth was switched on, keep it unswitched not less than 5 min.
4. Unsolder the short from the pin 10 of IC A5 at the oscillator's PCB.
5. Switch the synth on and measure with the digital voltmeter the negative voltage at pin 4 of IC A5 relatevely GND.
6. At pin 5 of IC A5 with the help of trim pot R10 set the negative voltage calculated according to the formula using the correcting voltage taken from the table for the certain temperature of that room where you make tuning.
Where U2 - voltage at pin 5 of IC A5;
U1 - voltage at pin 4 of IC A5;
U - voltage taken from the table for the cirtain air temperature.
Example. U1=-650mV, t air=25 deg C.
From the table for 25 deg C find that U=50mV.
At pin 5 of IC A5 with the trim pot R10 set the voltage MINUS 600mV relatevely GND.
t, deg. T
At pin 10 of IC A5 will appear +10:12V.
7. Switch the synth off. Solder the short on its place and switch the synth on. After 1:2 min at pin 10 of IC A5 the voltage will decrease and voltages at pins 4 and 5 become equal. This tells that thermal stabilizer is working well.
Thermal tuning for the second oscillator is the same.
After thermal tuning of the OSCs you can tune scale and pitch.
With normal working scheme for the thermal stability the synthesizer is coming to right pitch after switching the power on in 5 minutes.
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