When to recap?

Thanks everyone for the suggestions. Based on the consensus, I called a McIntosh service center that is about 40 miles from me. I have a Saturday morning appointment with one of their technicians to bench test the amp. The tech told me he does not subscribe to the theory of replacing everything. According to him, that's just a ploy for income purposes. I thanked him for his honesty.

He informed me by bench testing the amp, he'll be able to tell what should be replaced. A lot of what he told me over the phone was a little "Greek" to me, but I recall him emphasizing the importance to make sure the output transformers are functioning properly.

I'll post his findings after meeting with him. Thanks again all!!

Sounds like you found an honest shop Good luck.

A ploy for income purposes??? That is baloney. It is true that many Mac solid state amps have G.E. computer grade electrolytics in the main power supply that can last quite a long time. The axial tubular caps in your Mac should be replaced. The rubber gaskets crack and the electrolyte in the caps dries up. Power output can decrease as well as having heatsink temperature issues. I never say anything like that to my customers.

The McIntosh tech's statement was a ploy, to get you to bring the amp to his facility. Electrolytic capacitor manufacturers, in their data sheets, will specify an expected lifespan(in hours) for their capacitors(during use), at a certain temperature. No one ever expects their capacitors to last 40 years(or even close). Aluminum electrolytics also exhibit a limited shelf life. Here are a couple of articles that you may find instructional: (http://www.emersonnetworkpower.com/documentation/en-us/brands/liebert/documents/white%20papers/sl-24630.pdf) (http://digital.library.unt.edu/ark:/67531/metadc3104/m2/1/high_res_d/thesis.pdf)

I should have qualified my statements by mentioning that
your
caps, in those 40 years, have gone through a combination of
those two dynamics. In other words; what would be
considered,
"time in service" and "shelf life",
assuming that the amp was not constantly powered up, or
completely unused, in those years. Thus; they will have
gone
through the dielectric deterioration(storage) and healing
process(during use), a multitude of times. Then there's the
factor of the electrolyte drying out, over those years.
Bottom line:
Replace your electrolytics(at least)! Your ears will thank
you.