4047VCO

gated-astable mode VCO

This is an otherwise standard analogue triangle-core VCO design with a 4047 CMOS IC in gated astable mode shoved in the middle.
The oscillations are 'gateable': when given a trigger or gate the oscillation will complete one cycle then repeat if the gate is still present. Using the GATE and/or RESET inputs acheives various interesting effects from a pseudo-resonant filter kinda sound to mimicing a simple on-off VCA.
With nothing patched into GATE it will run freely like a regular VCO.

There are 6 outputs:
TRI1: triangle, SQR: square, PLS: pulse-width modulated output,
TRI2: sub-octave triangle, Q: sub-octave square, !Q: sub-octave square (opposite phase)

LIN, EXP, GATE, RESET, PWM are inputs.
The GATE input is held high with nothing plugged in, but when a cable is inserted the VCO will only run when the GATE in sees more than approx. 1V
RESET only affects the sub-octave outputs: TRI2 and Q will be held low and !Q held high while RESET sees more than approx. 1V
EXP input is for 1V/oct CV
LIN input (with attenuator) for linear frequency modulation note: LIN input is inverted, +ve CV will lower frequency, -ve CV increases frequency.. oops!
PWM input (with attenuator) controls pulse width of PLS output, PW pot sets initial pulse width.

CAL trimmer accessible from front calibrates 1V/octave tracking. Expect at least 3 octaves of good tracking using 3300PPM 2k tempco resistor for R17 in good thermal contact with Q1. A dab of the dreadful white goop recommended between them.
C1 should be a good quality C0G/NP0 cap. Using 10n for C1 and 4n7 for C3 gives a range of approx 25 seconds per cycle up to around 10kHz.
8HP +12V 20mA -12V 15mA

https://isaacbeers.square.site/product/4047vco/9