Two Arp Odysseys
Two Arp Odysseys
Two Arp Odyssey monosynths passed over my workbench at about the same time.
They are both first-generation Odysseys, also known as the Mark I. Initially, ARP manufactured them with a white front panel, with black lettering. Right before they switched over to the Mark II model, they changed the panel to dark brown or black, with gold lettering. Otherwise, both of these Odysseys are identical.
Both of these Odysseys had major issues. The black one would turn on, but was extremely unstable. It could make noise, but that's about it. Most of the faders were stuck, and many of the keys were clunky, or didn't move.
The white one was literally falling apart. Most of the chassis screws were missing, and there were wires and boards falling out all over the place.
Usually I would start a repair job by looking at the power supply. However since these synths were in such bad shape, I decided to disassemble everything down to the circuit board level, and build them back up.
Dirty Faders
Dirty Faders
While looking at the circuit boards of both units, it became apparent that the faders would need serious cleaning, or replacement. They were all caked with decades of dust, hair, and food. Click on the photo to see a closeup of the gunk.
Simply cleaning the faders with contact cleaner would not be a long-term solution in this case. Therefore I decided to remove and hand-clean each one. For faders that were beyond cleaning, I bought after-market replacements.
Odyssey Circuit Boards
Odyssey Circuit Boards
Removing the faders from the boards was a job in itself. In addition to the electrical connections, there are 2 metal tabs on each fader that are soldered in place for mechanical stability. This photo shows the 3 boards of the white Odyssey, with about half of the faders removed.
Open Fader
Open Fader
After much practice, it's possible to remove the metal clips, and open the faders without destroying the plastic casing.
Inside the casing is the actual slider, a track for the slider to follow, and a conductive strip. To clean everything you'll need isopropyl alcohol, some non-shredding cotton swabs, and a lot of time.
Lots Of Faders To Clean
Lots Of Faders To Clean
Here are all of the faders from the white Odyssey. The one in the plastic bag is an aftermarket replacement. It's almost exactly the same in size and feel, to the originals.
Under each key on a keyboard, there is usually a metal or plastic tab that keeps all of the keys at the same height. It is extremely annoying if one key is a bit higher or lower than the others.
There is also a rubber ring (or felt pad) that is slid onto the tab. This keeps the keys aligned, and stops them from 'clunking' when you play them. This ring is called the bushing.
Both the white and the black Odysseys had very bad keyboards. The key heights were all over the place, and keys were either clunking a lot, or were stuck down.
It turns out that on the white Odyssey, all of the bushings had started to dry out, decay, and turn into dust. On the black Odyssey they were melting, and turning into a gooey mess. I removed all of the old bushings, cleaned everything with alcohol, and put new bushings in place.
At this point I replaced the capacitors on both power supplies, and put the synths back together. Both of them would now play, somewhat, but there were a lot small issues.
The sample-and-hold and pink noise didn't work on the white Odyssey. Notes were drooping a lot in pitch on the black Odyssey, and it was jumping between octaves. There was a lot of glitching of notes on both Odysseys.
Solving these types of issues requires a lot of experience, thinking, and patience. Having a service manual is also extremely helpful, as you can trace the signal path until you find the problem.
Odyssey Octave Switch
Odyssey Octave Switch
The sample-and-hold and noise issues were due to bad transistors. The drooping pitch issue was caused by a bad capacitor in the keyboard voltage-hold circuit. They keyboard contacts on both Odysseys were all over the map and needed adjustment. That is what was causing the glitches.
Finally, the octave jumping was caused by a dirty octave switch on the black Odyssey. I took it apart carefully, cleaned all of the surfaces, and put it back together.
Arp Odyssey Repair
Arp Odyssey Repair
