Transcendent T2000 Synthesizer

A sort of a wet dream, the very simple but also very competent T2000 synthesizer, describes in ETI in 1978 and
available as a kit from Powertran.

The machine had just one VCO but was still capable of producing a lot of great sounds.The features are described in the articles below.

I have been working on cloning the original synthesizer for many years. The first notes about the idea was made in 2018 but it wasn't until Fall 2021 I seriously took a firm grip on this project and went ahead

I used the PCB layout from the articles as a backdrop in my PCB-program - Sprint-Layout 6.0 and just laid out the traces on top and successively made necessary adjustments and modifications.

First I hade to make the board shorter as the program only accepts boards up to 500mm - that was rather easy done. Next I made the board 2-sided with all empty space as a ground plane (hope that works fine).
As I couldn't find the kind of slide switches used in the original I picked the kind used in the Concertmate MG-1, bought cheaply from China (links below) and made adjustments accordingly.
Other modifications was changing the layout for trimmers and changing from transistors BC182/212 to 2N3904/06. Instead of the odd combination of resistors making up the temperature compensation I went for a simple single PTC, 1K resistors and placed them closer to the CA3086s.
Finally I tried to make notes on the board to help find the correct potentiometers and trimmers.

When done, I triple-checked the board to the schematics, and shipped the gerberfiles to JLCPCB ordering a set of 5 boards in purple (the fashion color of this year). Unfortunately,

SCHEMATICS

The ETI articles with full info (pdf).

GERBER FILES

Gerber and drill files zipped - corrected 2022-02-02

BIGGISH, 7MB image of top layer

PHOTOS

The diagrams I had to work with:

Part of the work in Sprint-Layout (green - solder side, blue - component side

Final result and the build process:

The potentiometer exles are too short and I have to fix that. Got an idea.

Here's my keyboard and the size is perfect for the board. There's room for MIDI-ins/outs to the left and Power ON/OFF and headphone connector to the right

As my keyboard has 41 keys whereas the original had only 37 I think this will solve the problem with the 4 extra keys. Still have 24R7 resistors in the chain, but adjust R10 so the total resistor in the loop is unalterted. That should give the required voltage/key drop.