Aries AR-338 Phase
Modulated Sync VCO

Aries modules were available both as kits and factory modules.  This module did not appear in the 1978 catalog and sold in 1980 for $238.80 in kit or $358.80 assembled.  This module appear to be a kit.


I can find no user manual for this module.


AR-338 PMS VCO Schematic


The PCB has a full ground plane on the front with legends etched in reverse.


The PCB rear also has etched legends making it quite easy to work on.




There are 5 trimmers to calibrate this module. They are: T1 Triangle Symmetry; T2 Sine Symmetry; T3 Sine Shape; T4 Initial Frequency; T5 V/Oct; T6 HF Tracking.

AR-338 PMS VCO Calibration Instructions




This VCO has a number of waveform output. It has the standard ramp, pulse, triangle and sine wave outputs.


It also has a Pan output. There are two pulse generators in this VCO.  The pulse generated from the ramp appears on the front panel. The pulse generated from the triangle does not, but goes to a pan circuit which pans between the two pulse outputs. In these scope photos, the cyan trace is the internally generated pulse from the triangle. The pan outputs are derived from various setting of the pan and pulse width controls. This first image is with the pulse width controls set to 50%.


These next two images are with the pulse widths set to 25% and 75%.



I modified the soft sync circuit as you had to be very close to the frequency for the VCO to lock. I decreased R41 to 24K as per the SSM-2030 datasheet. The yellow trace is the ramp output and the cyan is a reference oscillator. They differ by 7.4 Hz or 5%.


Using soft sync pulls the PSM VCO to synchronize it with the reference oscillator.


This image is showing the VCO higher frequency ramp locked to a lower frequency reference oscillator using hard sync.


This image shows a second low frequency triangle as the modulation source for the hard sync. You can see the ramp shift between hard sync and no hard sync corresponding with the triangle wave.