Oberheim EVS-1 Eight Voice Synthesizer w/ Extras

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video upload by Isla Instruments

via this listing

"** Note that SEM #2 in the photos seems to be missing the caps from the 2 frequency pots.
these are not missing and I had forgot to mount them before taking the photos. Rest assured they are included.

Up for sale is a complete, eight voice SEM system including FVS-1 and #4 voice Expander module, cabling and accessories.

History
Over the course of the past year or so, countless hours have been spent on this illustrious EVS-1 system to restore it back to its former glory (perhaps even better)

It was purchased by me (Brad Holland of Isla Instruments) as part of a huge inventory buyout of a synthesizer musuem (Audio playground, Orlando; which had closed its doors in around 2000) during covid when I couldn't purchase any more semiconductors to make my existing (S2400 sampler) product. and had been sat stored and forgotten about for many years (at least since 2001).

Great care and attention has been afforded to the restoration, and this is truly a museum worthy collectors piece.

Here's a non-exhaustive list of works carried out.


General Repairs
Every single board has been recapped and repaired.
When I say every single board, I mean everything from the internal power supply, to the programmer boards, the sems, the output module EVERYTHING has brand new caps throughout.
This means that all electrolytic and tantalum caps were replaced, along with most of the 'tropical fish' capacitors found throughout the synth as they were starting to fall apart.
Swathes of logic and linear ICs replaced. In every case a high quality milled IC socket was used, making future repairs much simpler as no desoldering will be required.

Internal power supply completely rebuilt with every single component down to the external power transistors replaced for new.


Potentiometers rebuilt with BRAND NEW carbon trace pcbs.
In all honesty, this wouldn't have been absolutely neccessary, however, I made the mistake of cleaning all the pot/control panel boards in my ultrasonic cleaner.
In itself not a problem, however, I had the heat turned on when I did this which lifted a lot of the carbon tracks from the insides of the almost 50 year old pots, ruining them. As a result I had a company in the UK (Blore Edwards) remake brand new carbon track Pcbs for me to re-build all the pots with, which makes them essentially brand new in terms of electrical conductivity.

The Pratt-Read keybed was completely stripped, cleaned and rebushed and lubricated with dow-corning molykote grease making the synth play like brand new.

The original programer battery was still in the synth, long dead of course, as it expired in 1989. This has been replaced with a lithium cell in holder. This is cable tied to the rest of the loom rather than soldered onto the programmer board, 2 boards deep. It shouldn't need replacing for at least the next 10-15 years, but when it does, SEM1 can be unscrewed to gain access to the cell to easily replace without dissasembling modules and pcbs.

Exterior Restoration
The road case the system is mounted in was in a sorry state (see one of the last photos).
It was stripped, re-tolexed and has completely new hardware, handles, clasps, hinges, feet, washers and screws throughout. This is supplied with keys to unlock the clasps.
I was unsure about using the usual rivets that are used with road cases like this, given the age of the wood, so opted to use 'blind tee nuts' these are threaded inserts that claw themselves into the wood as you tighten them with machine screws. As a result, I trust the hardware and hinges to offer fantastic support to the rest of the system if/when being transported.

Modifications
We have replaced the original AC inlet with a modern IEC type C-1 socket, We feel this a worthy modification that is not only safer by design, but also means you won't be paying over $100 for a replacement power cord should you need one.

There are 8 toggle switches above the programmer, each one of these switches is connected to the polyphonic keyboard assigner module. When a switch is thrown this tells the assigner that that particular SEM is 'busy' and so won't get notes assigned to it.

We have found some documentation on the web about this mod and rather than remove it, we just left it there.

Lastly, there is a switch and pot for each VCO (1&2) that takes the VCO pulse wave from SEM1 and feeds it (through the pot (Depth) to VCO modulation of all the other SEMS essentially giving FM capabilities.
Again, this mod had been done at some point in the past and has been left in place.


In addition to all of this, of course, the system has been fully calibrated per service documentation recommendations and is ready to play.

Also included in the sale.
- Schematics (both original and re-printed material)
- Service/calibration Documentation,
- PCB blueprints,
- Cabling (inter-unit and power cables)
- Oberheim Voltage control pedal
- Original Oberheim factory patch cassette tape"