MATRIXSYNTH: PAIA 4700 Modular Synth

Monday, April 13, 2020

PAIA 4700 Modular Synth

via this auction

"Vintage PAiA 4700 modular synth. As far as I can tell, these were DIY modular synths first released in 1981. These are somewhat quirky machines, and can produce some really interesting and creative sounds. Note that these use the hz/v CV standard (notably used on the Korg MS-20) rather than the modern v/octave standard. The two-part telex case conveniently closes up for easy transportation.

This unit comes with the following modules:

4710 - Balanced Modulator (x2)
4711 - 4/2 Mixer (x1)
4712 - Spring Reverb (x1)
4720 - VCO (x3)
4730 - VCF (x1)
4740 - Envelope Generator (x2)
4761 - Wing (x1)
4770 - Watt Block (x3)
4780 - Sequencer (x1)
Control Oscillator/LFO (x1)

I do not have proper testing equipment and therefore can't fully assess the functionality of the machine. However, as far as I can tell, all modules are fully functional except for the following:

4720 - VCO: one of these seems to output saw waves from the triangle and sine outputs (the other two seem to be fine).
4770 - Watt Block: the power indicator LED does not work on one of these, and I suspect that it may not be delivering full power to the sequencer, which is having issues as a result.
4780 - Sequencer: It is sort-of possible to use, but due either to insufficient power or to a wiring issue, there are glitches (steps skip halfway through), and the switches don't seem to work as they should (the sequencer runs when the switch is set to "off").

Given the above issues, this synth is being sold as-is. Having taken a look inside, someone with modest soldering skills should easily be able to make fixes if they could identify the problems - these synths were sold as DIY kits and feature simple hand wiring. Schematics are available online.

This machine is in 7/10 cosmetic condition - there is some scratching on the front panels (looks much worse in the photo than in person), a few missing screws, and the telex is lifting on the outside corners of the case."

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