This module is based on the Aries 329 Phase/Flange. The main differences are in semiconductor component selection
and it is all 0805 & SMD, otherwise it is pretty close to the original. The schematic for this module that can be easily found on the net has a component PD10, with 2 + terminals and 2 – terminals. Searching for this component shows a full wave bridge rectifier……hmm…. can’t be right, though reading various DIY forums shows few people were sure and there do not seem to be any online photos of the 329 PCB. It turns out PD10 was a resin block 10 stage phase shift network available in the late 70s. The Tau pipe phaser had two and the phaser in the Arp Quadra had one.
The Arp Quadra Service manual shows the internals and that is what is used in this module. Normally I would avoid any circuit requiring 11 matched NPN transistor pairs, at least since the LM394 was discontinued, but now we have the BCM847, which is cheap and matched.