One of the best sounding polysynths ever made, recently electronically restored to the highest standard. This OB-X is fitted with a full complement of 8 voice cards, and includes both a Kenton MIDI retrofit and Oberheim's own Serial Buss port. Functionally the OB-X is in very good condition. The keys and keybed have been thoroughly cleaned, re-bushed and realigned. All the front panel controls are smooth and operate cleanly. The sound, needlessly to say, is phenomenal and the synth is a pleasure to play.

Almost uniquely for an OB-X this example has been manufacturer retrofitted with the Oberheim Serial Buss port, Oberheim's own pre-MIDI connection system that debuted on the OB-Xa. (You can see this actual instrument make a brief appearance on Alex Ball's Oberheim documentary where he discusses the interface). This has not been tested (due to a lack of compatible Oberheim equipment available to do so), but is correctly wired-in. In addition there is a fully working Kenton MIDI retrofit kit installed, with MIDI sockets added neatly into the rear of the case.

Cosmetic condition is average for a gigged OB-X, the easily scratch-prone black paint is worn in places, though the only significant scratches are two to the front panel (see pics). There is a small crack to the corner of one veneer/chipboard end cheek, and a slightly chipped edge on the other. One white key has been replaced during the restoration and is very slightly off-colour, but this is unnoticeable other than in very bright lighting.

Prior to sale the OB-X has spent some months in the hands of synth tech Harry Axten of HKA Designs, one of three OB-Xs he has restored in the last two years. A full list of work undertaken is given here, and the synth is also accompanied with full service records from the 1990s, including the Kenton installation.

Work done by HKA: - Removed MIDI retrofit while undertaking restoration work. - Removed all boards to clean cabinet thoroughly, cleaned out dust, metal swarf from when holes for MIDI DIN sockets were drilled, etc. Cleaned knobs and panel switches. - Rebuilt power supply with new (higher-power rated) bridge rectifiers, electrolytic and tantalum capacitors, trimmers, backup battery and associated diodes. - Power supply was tested and found to be in spec, however IEC inlet started crackling – usually a sign of the internal suppression capacitors failing, so this was replaced. - Replaced all electrolytic capacitors and tantalum capacitors throughout. Replaced any Mullard ‘tropical fish’ film capacitors showing signs of deterioration (cracks, flaking, exposed dielectric, etc.) with Wima MKS4 series parts. - Replaced any header pins which had previously been soldered to. Built new cables to replace the missing ones and replaced the wires and crimp terminals in most other cables, especially the ones between the panel boards and the ones connecting the voice motherboards to the lower processor board. - Incorrect hardware on upper voice motherboard replaced with the correct parts, and any other missing or damaged fasteners replaced, including the side panel screws and cup washers. - Re-soldered joints for all header pins on voice motherboards. Replaced two voice pan trimmers on upper voice motherboard which had previously been replaced with huge control pots bodged in with flying leads. - Replaced all frequent-failure ICs on lower processor board: LM324, TL084, CD4051 and CD4053. Replaced frequent-fail DIP switch for voice enables on panel board. Also replaced all single-turn trimmers on lower processor board. Pulled and tested all digital logic ICs in out-of-circuit tester, revealing 1x failed AM9111BPC, 1x failed CD4049 and 1x failed 80C98. - Keyboard was removed and all keys washed. Several keys needed replacement. All key bushings were replaced and the key stops re-aligned. Keybed cleaned and contacts polished. - All single-turn Bourns trimmers on voice cards were replaced with Piher PT10 trimmers or Bourns 10-turn trimmers (for VCO init. freq. and hi-track adjustments). Each voice card was then tested and any issues were resolved, including failed volt/octave trimmers on one card, preventing the oscillator scaling from being brought into correct range, plus various failed voltage regulators, op-amps. One voice card required the header connectors be replaced as originals were completely bent out of shape and wouldn’t make a reliable connection to the pins. - Full calibration and reloaded factory presets. - Reinstalled MIDI retrofit. - Full functional test and soak test.

This is a truly great synth at a great start price.