I bought my D52B and SP6 in 1979. After 34 years it's possible that ARC cannot easily source the parts you need, I assume you asked ARC? I have spoken with Kalvin numerous times so I am not sure it is fair to generalize about their customer service. The large blue electrolytics are Mallory if memory serves. I thought it was a great amp in its day but a used ARC 100.2 would be a cost effective "in house" substitute.
Audio Research D-52B: any suggestions for caps?
My old Audio Research D-52B is now considered "End of Life" by the manufacturer. I need to replace some large power supply capacitors (60,000 uF 40V) that are no longer available. While I'm at it I may re-cap my Audio Research SP-6A. I'm not up to date on the state of capacitors and high end manufacturers. Can anyone offer suggestions for replacing old aluminum electrolytic capacitors (e.g. 2200 uF 100V, 200uf 450V, 300uF 300V). Not all are screw mounts. I am the original owner and have the schematics and parts lists for the D-52B and SP-6a/b. I also have MG III b's whose crossovers probably could use re-capping.