Audio Research or Luxman?

Yes , check the bias on the KT150s is on point , additional expense I appreciate however pre 1990 production S Petersburg reflector 6h30- DR make a significant upgrade in fidelity compared with the ARC supplied later production tubes 

tastes change, there will be a ready market for the ARC gear. A competent tech should be able to gin up working potentiometers. Music Reference still has some NOS Nobel pots in tock, both stereo and mono in a variety of values. Just my $ or ¥
 

I am a discrete ladder robot in a continuous arc about the Sun

Also, check FleaBay, many Japan vendors of vintage Luxman gear, perhaps they have a line on parts in country…

Thanks for all the comments so far. I recently purchased both ARC's used, and had both serviced by an authorized dealer. All tubes measred well, and bias settings are correct and have barely drifted since acquiring the amp.

The original pots are from Alps and not longer available. I'd try finding Japan sources. Do you, tomic601, have more information on that or Fleaboy?

I should state that I am thrilled with the sound quality of my ARC gear.

Erik: are you predicting each of the current 505, 507, and 509 will be phased out soon?  They all still say “ New” on the site.