ARP Odyssey Model 2810 Synthesizer

ARP Odyssey Model 2810, 1975

I bought this synthesizer in Boston in 1977 while attending the Berklee College of Music. I was interested in electronic music and this instrument allowed me to explore an amazing variety of sounds using the very logical layout of its controls. The front panel clearly shows the signal flow with labeled block diagrams for each functional section of the synthesis process.

For ten years I used this keyboard for creating a broad spectrum of musical sounds and sound effects while recording music I wrote until a radical change in my career path. For another 29 years this Odyssey was hidden away in a closet. Having time now to pursue long-overdue personal projects, last fall I disassembled it and restored it to a fully functional instrument. An advantage to living in Tucson, Arizona is that the very dry weather was great for conserving the condition of this vintage machine.

ARP Odyssey disassembled (power supply not shown)

Although it had been stored safely away, during restoration I found quite an accumulation of dust and hair from its previous heavy usage. Here’s a good comparison of the before and after state of some sliders on the front panel.

One thing that dramatically improved the playability of the keyboard on this vintage instrument was replacing the bushings. After 41 years, the bushings had dried out completely. This not only rendered the keyboard tactilely sloppy, but made it distractingly noisy, too. To remove the bushings, I used a crochet needle. It is strong, doesn’t bend, and has a nice, smooth-edged hook on the end for grasping the bushing. Still, the bushings were difficult to remove and didn’t come out in one piece as the following picture shows.

Odyssey keyboard bushings removed

Here’s a close-up of a new bushing on the left and old one on the right standing on their ends. They’re about 1/2″ long with a rectangular hole through their length to slide onto the tang on the keyboard assembly. Notice how the two “ears” on the bottom of the old one are flattened and offer no cushion for the impact when the key is pressed. Also, I imagine they were all black when new so they’ve dried out and lost all their rubbery resiliency.

New and old bushings

I captured the before and after condition of the keyboard on video during restoration. See how the new bushings removed the sloppiness and you can really hear the difference, too.

Adjustments were also necessary to the Trigger and Gate wires on the underside of the keyboard. Here’s a picture of the wires of all the keys and the Trigger and Gate busses running from left to right supported by the white standoffs.

After removing all the keys, replacing the bushings, and realigning the keys, I found that pressing any key in the upper half of the keyboard did not change the pitch. The pitch was locked on one key in the center of the keyboard. Standing the keyboard up on its side allowed me to see that the Trigger wires on a couple of keys were in constant contact with the Trigger buss. On this generation of keyboard there are two wires for each key: Trigger and Gate. The Trigger wire should contact the Trigger buss before the Gate wire contacts the Gate buss and then they should separate from the busses when the key is let up. The video below shows the movement of these wires on three keys. The first key pressed on the right is properly adjusted. The two keys to its left show that the Trigger wire needs adjustment. All keys should be checked, of course, to ensure that this sequence is correct.

I also replaced two sliders; one was not working and the other just had a part of the stem broken off so it was difficult to operate through the front panel. Here’s a picture showing all the parts of one slider. The C-clamps at the top hold the two halves of the slider body together and were very carefully pried open to get at the insides.

Odyssey slider

I found that the C-clamps on the new sliders were slightly different. The shoulders of the tabs that are inserted through the circuit board were taller. This prevented a good seating of the slider body against the circuit board and this made the stem stick up less than the original sliders on the panel. See the photo below that was taken before I filed down the shoulders to match the originals.

New and original slider ends

This 1975 Model 2810 synthesizer contains the desirable 4035 filter. There was some dispute with Moog at the time and subsequent models had other filters installed that some think are inferior to the 4035.

Desirable 4035 filter

Before reassembling all the refurbished parts I noticed that the adhesive of some of the standoffs on the underside of the front panel that support the circuit boards had separated from the panel. I pulled the large nuts and adhesive pads away from the panel as seen in the picture below (see the gaps). You can also see that the standoff in the center was already repaired by “EP” when this instrument was first built. I did the same epoxy repair as “EP” did for the separated standoffs.

Separated adhesive

Once back together, I used the ARP Odyssey Service Manual found online to follow trim procedures and verify calibration of the circuits. This was very helpful as recalibration was needed to correct several adjustments like the voltage across the keyboard. The three-octave spread was flat and the 2-octave transpose switch didn’t quite get there either. Here are shots of the calibration of the +15V power supply and the VCF V/OCT trimmer for 800Hz.

+15V supply calibration

VCF Volt/Octave calibration