Knowing all too well from having serviced quite a few ARPs, it's a daunting task having to restore the CTS slide potentiometers. If the carbon element is in decent shape, then it is doable: desolder, fight the little twisted side tabs to get the rounded shape out of the square hole, carefully pry open without breaking the brittle molded tab retainers, open and clean out the gunk, relube, reassemble, reinstall, and resolder. Then repeat, 15, 25, maybe 30 odd times depending on the synth. It's ruthless!
Having heard the idea proposed before, I decided to make my own PCBs to serve as adapters to fit modern Bourns PTL sliders into the CTS spots on the original ARP PCBs.
The PTL series are a popular, readily available slide potentiometers that include LED indicators in the slider itself.
I'm currently in the process of installing and testing the boards in an ARP Omni 2. Once this is complete, I'll be offering the adapters for sale in completed kits, as single items assembled with the PTL slider included, or just as the PCB's themselves.
Included in the kits and available separately will be a simple LED driver board utilizing an LM317 regulator and small trimmer to control the brightness. Multiple drivers can be used if different colors (requiring different currents!) are desired. Changing the color is a simple matter of swapping out the 2x3x4 mm box LED.
Plans are also in the works to offer a set for the Juno 106...there's just the nasty problem of working out how to deal with the HPF franken-slide-switch. I think it's possible to alter a PTL to do this...I just need to dedicate some bench time to cutting up a few PTLs.