All posts in category Synths and Keyboards

Oberheim Four Voice (FVS-1) Restoration – Part 8: The SEMs


In the spirit of saving the easy stuff for last (…or so I thought), I tackled the restorations of the four Synthesizer Expander Module (SEM) units.  These were more work than I had anticipated, but then again I opted to completely disassemble them, clean, re-cap, and repair any issues along the way. Fig. 1 – […]

Oberheim Four Voice (FVS-1) Restoration – Part 7: The Programmer


In 1976, the Four Voice began being offered with a programmer module.  Oberheim’s  patch storage implementation was a bit different from that of the microprocessor-controlled polyphonic synths to follow (Prophet-5, OBX, etc…) in that it was capable of  multi-timbral storage/recall of sounds.  In other words, each SEM could be setup differently using the programmer’s controls […]

Oberheim Four Voice (FVS-1) Restoration – Part 6: Cosmetology


I’ve been making some progress on this restoration, and thought I’d lump together a bunch of the more superficial, cosmetic-oriented work in this post. While I’ve had the synth chassis separated from its roadcase, I felt that it would be a good time to freshen things up a bit.  The I/O and power supply panels […]

Oberheim Four Voice (FVS-1) Restoration – Part 5: Keyboard Rehab


Forging on ahead, I felt it was time to give this keyboard some new life.  The bushings were pretty much shot, and several were starting to crumble away – yielding the all too familiar snaggletooth keys and loud metal-on-metal action:     Getting the Four Voice’s keyboard assembly out involves excavating the synth from its […]

Yamaha CS-40m


These are some photos of my old CS-40m.  I loved the filters and ring modulation in this synth, and it was built like a tank!  The design lacks some niceties like FM and sync between VCOs, but it was still a joy to play.   This synth also interfaced well with my modular.  Here it is with […]

Oberheim Four Voice (FVS-1) Restoration – Part 4: Hearing Voices


Now onto the fun stuff…  I’ve been seriously digging this thing even as it limps along with two-voice polyphony, but its time to hear a happy quartet of SEMs! SEMs 3 and 4 were not firing from the keyboard, and the continuous assignment mode would only step between SEMs 1 and 2.  Between all of […]

Oberheim Four Voice (FVS-1) Restoration – Part 3: The PSU


  Before venturing too far down the path of sorting through the faults, I wanted to first ensure that the power supply was in good working order – that the power output was clean, and that the rails were putting out the correct voltage. There are a total of six capacitors on the PSU board […]

Oberheim Four Voice (FVS-1) Restoration – Part 2: Modification Removal


Well, where to begin… I thought I’d start by tracing out and removing the modifications.  Overall, the mods looked to be in a questionable state, and I felt it would help in troubleshooting the primary issues if I could rule-out the modifications as a contributing factor. The “Mediamix Triangle Mod” board was held in place […]

Oberheim Four Voice (FVS-1) Restoration – Part 1: Introduction


I’ve been fascinated by this synth most of my life, and I finally got a chance to lay hands on this one in June 2011. In or around 1975, Oberheim released the four voice polyphonic synthesizer (dubbed the FVS-1), which was basically comprised of four Synthesizer Expander Modules (SEMs; keyboardless, monophonic synths that were originally […]

Modular Synth Walnut Cabinet Refinish


I had obtained a 44-space walnut studio cabinet slated for the top-most portion of the modular.  This cab had originally been purchased from, and it appeared to be very well loved with its share of road rash (and some extra holes from those Dotcom mounting brackets). My current cabs are still in great shape, […]

Sequential Circuits Pro-One Pressure Sensitivity Retrofit


My Pro-One had died a ways back (an op-amp in the keyboard’s CV path had bit the dust), and while I was in there repairing it and doing some other maintenance (PSU filter caps, keyboard bushings) I was thinking that it’d be slick to try and add pressure sensitivity to it.  Having just finished refreshing […]

1974 Minimoog Model D Refinish


I acquired a 1974 Minimoog Model D that plays and sounds absolutely amazing, but this thing was really rough in the looks department.  I had to get into it to repair its volume pot (it had been replaced with an 16mm center-detent pot of the wrong value) and do a couple other minor things, and […]

Pro-One Easter Eggs


I remember reading somewhere about the hidden Easter eggs etched and screened on the PCB of the Sequential Circuits Pro-One synth.  These are only visible when the board is completely removed from the front panel. Here are some photos I snapped while mine was in pieces for servicing…   Chenrizig:   I believe this is […]