I'm thinking here both repairing a non-functioning or damaged McI amp or just bringing it back to specs with new caps, etc.
I did a Search here and found some options in a couple of threads but no dedicated thread on the topic so thought I'd start one to see if there are additional viable options that were missed.
I know Brad Sarno has done right by many here updating and upgrading our McI amps.
One post referenced ctech-electronics-store (eBay name). Another referenced lionrr12 (eBay name).
And my salesman at my local high-end stereo store (which sells new McIntosh equipment and also Focal speakers which I bought and love 'em) highly recommends Audio Classics in New York.
But that's all I could find on my own.
Disclaimers: I'm happy to share whatever relevant gear knowledge or experience I have. Genuflection/payment/proof of worthiness neither sought nor accepted. I don't design, build, market, sell or endorse for pay any new music product or service. I occasionally sell personal used gear. I am an unpaid endorser of SoundScaper Productions and Godfrey Daniels Guitarworks.