“This unit, serial number 1010-0078, is the final production version of the Prophet-10 designed around two Prophet-5 Rev 3 voice boards. It has enhanced microprocessor control circuitry and software to provide 10 polyphonic voices (2 VCOs each) in four keyboard modes with responsiveness comparable to the Prophet-5. These modes allow the choice of separate polyphonic control of two 5-voice synths, combined control of a “stacked” pair of 5-voice synths, alternating notes between two 5-voice synths, or control of a single 10-voice synth. Additional features not found on the Prophet-5 include programmable 3-band equalization, two control voltage pedal inputs with assignable routing, three foot switch inputs and a 10,200 note polyphonic sequencer. It is equipped with Sequential’s MIDI interface kit and the latest firmware, Rev 6.1. Recently the unit was thoroughly tested, repaired and burned-in by Wine Country Sequential in preparation for sale.
If you are familiar with the Prophet-10, you are probably wondering what happened to the keyboards on this unit. Although the stock Prophet-10 with its twin manuals is a sight to behold, the inclusion of two keyboards makes the nearly 3-1/2 foot by 2 foot by 8 inch, 70 pound unit so cumbersome that it is difficult for one person to move it by themselves, and difficult to integrate into a small studio environment or performance setup. As well, with the advent of MIDI controllers and sequencers and availability of the Prophet-10 MIDI upgrade kit, the built-in keyboards became redundant. At least a few ardent but frustrated Prophet-10 users dreamed of a slimmer instrument without the keyboards.
While I was employed as a service technician and visiting E-Mu Systems in the late 1980s, I happened to mention this to a product design engineer there who described to me a simple solution he referred to as “The Riley Mod.” It turns out that all the structural members forward of the main control panel can easily be unbolted and removed except for the sides of the chassis frame. The keyboards, modulation wheel and sequencer modules are simply unplugged from the rest of the synthesizer, unbolted and removed. Then the sides of the chassis frame can be cut back in line with the new forward face of the enclosure created by reusing a long corner piece and sheet metal that was part of the keyboard enclosure. Likewise, the wooden end pieces are carefully cut back to match the new enclosure dimensions and refinished to match the original look. Voila!
As you can see in the photos, the end result resembles an Oberheim Xpander, but with the familiar Prophet-10 control panel and no keyboards. This reduces the depth of the instrument to 13-1/2 inches and weight to 43 pounds – a much more practical size for lifting, transporting and integrating into an electronic music studio or performance system. For example, this slim rendition of the Prophet-10 rests comfortably on an Apex column stand.
NOTE: The circuit boards contained in the synthesizer unit are unaffected by the “Riley Mod” and have not been modified in any way except for installation of the factory-supplied MIDI upgrade kit. The MIDI upgrade and all servicing of the unit was performed by an authorized Sequential warranty service center. I performed the chassis modification while employed as a service tech at an authorized Sequential warranty service center, although this of course was not warranty service. In addition to the steps described above, minor modifications to the components removed from the original instrument were made to facilitate their continued use as separate modules. The Polysequencer was mounted in a custom enclosure made of sheet metal with wooden side panels, and the ribbon cable connecting it to the instrument was divided and terminated with cable headers so it can be connected by an extension cable. A selector switch was also added so that switching between internal and external clocks can be performed without unplugging and re-plugging the external clock signal cable. The single remaining keyboard (the other was sold) was mounted on sheet metal cut to the size of the keyboard’s footprint. An enclosure and external cabling similar to that provided for the Polysequencer was planned but no further work was done. The modulation wheel panel was prepared for addition of an external control switch but that and an enclosure with cabling were never implemented.
I am the original owner of this instrument and have kept it in smoke-free home studios or in heated storage at home. The instrument was used in a handful of public performances and has relatively little wear and tear. All rotary controls, switches and displays look like new and are in perfect working condition. The tape drive and Polysequencer are in perfect working order. All the white lettering on the control panel and black lettering on name plates is fully intact. Two of the four screws that attach the hinged control panel to the chassis frame are missing, and a nut for one of the screws is missing from the chassis frame, although the two remaining screws are sufficient to secure the panel. Some minor scratches or worn spots in the paint on the chassis and around the control panel screws have been touched up. Same for the Polysequencer. The instrument’s right wooden end panel has numerous light scratches and could be refinished to appear as nice as the left panel, which is still in very nice condition.” Auction ended. Click here to browse on eBay.