This is one of the machines which I would have liked to keep for my own studio but unfortunately I had to give it back to the friend I repaired it for.
Major overhaul, had to unsolder and pry open all sliders, clean them with q-tips and grease them again with Caig fader lube. That did the job on the scratchy pots.
Turned out that the Ringmodulator was not working. In order to fix it, I unpotted the unit (remember that on earlier Arps, the different modules are covererd in resin and silicone), which is quite a pain to do. I remember half of my living room beeing full with tiny bits of white silicone! Turned out that one of the transistors was out, but in order to get it going again I needed to replace all of the transistor pairs in question with newly matched ones since it seems that the circuit needs to be well balanced in order to get it properly working.
btw. I replaced the now obsolete transistors against standard ones and it works fine.
Other fault was the envelope generator 2 which had a bad opamp. No big deal, that one was not packed in resin and on the main board.
Truly an amazing sounding unit that ARP.
Did I mention that I changed all Tantalums and Electrolytes on that thing? Go figure out the amount of work since it means disassembling the complete unit and unsoldering all connections.
Pictures yet to be added.