Aries AR-332
Dual VCO

Aries modules were available both as kits and factory modules.  This module did not appear in the 1975 catalog and sold in 1977 for $179.00 in kit or $295.00 assembled.  This module appear to be a kit due to the build and solder quality.

I combined specifications from Robert Leiner (with permission), my photos, and a reverse engineered schematic into a PDF document.

AR-332 Dual VCO Document

 

Each ramp VCO is in a large potted module with a sync and 1V/Octave input.  The other pins consist of +/-15V, ground, output, and the timing pin so a larger capacitor can be paralleled for LFO operation.  The PCB circuitry consists of a dual op-amp for control voltage summation and ramp to pulse generation.  I was not able to tune this module to 1V/Oct with the single turn 50K trimmers and replaced them with 20K 20 turn trimmers (the VCO tunes to 1V/Oct with the trimmers set to around 10K so I reduced the value from 50K to 20K).

 

The PCB is a single sided tin with no solder mask.  Care is required when doing repairs as the pads do lift easily.  The VCO-B ramp output had low amplitude and significant DC drift which is unrepairable without depotting the module.  The extra op-amp and circuitry on the rear of the PCB is an AC coupled gain circuit to bring the VCO B ramp output back to 10V pk-pk and center it at +/-5V.

 

This scope image shows the VCO B potted module ramp output.  The amplitude has decreased to 7.4V pk-pk and it is centered around -6.5 volts.  This renders the pulse generation circuitry useless as it is outside the comparator range.  By AC coupling and bringing the signal back to 10V pk-pk the pulse circuitry operates correctly.

 

I AC coupled the ramp instead of using a DC level shift as I believe the DC drift might continue with time.  AC coupling makes the ramp output in LFO mode very non-linear but the pulse output can be used for narrow pulses at low frequencies.  This image shows VCO B in LFO mode at 0.117 Hz with a very nice pulse output.  Because of the AC coupling the ramp output has shifted negatively but still has a 0 volt DC average.

 

 

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