When to recap?

Former McIntosh repair tech, here.

Another clue; swollen tops of the electrolytics (can-type caps), and look for any dark liquid seepage from around the bases of the capacitors (some mfrs like NAD used a dark glue to help secure the cans, not McIntosh Labs).

All the internal PC boards WILL need solder joints retouched at their Molex connectors, and the carbon bias resistors (10, 12 or 15 ohms, depending on model, WILL have drifted if not replaced previously with metal film).

A properly biased McIntosh amp runs barely warmer than room temp even when driven moderately hard, so if the heatsinks are getting hot at all (or worse, one side heatsink warmer than the other), you need the bias circuitry resistors changed.

All the above will firm up the sound and re-focus the instruments better, as well as ensure future reliability and enjoyment.

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)