Indicators of worn/bad capacitors?

From your words, your capacitors are most-likely okay.

Caps going bad in SS amp will hum and possibly pick-up RFI noise almost just like tubes.

The other way is to look at those if they show any signs of heat impact, discoloration or deterioration of print. Electrolytic DC caps usually can show that they're getting little 'fat', showing some loss of liquid around it.

Did you leave it off all weekend and then come back?

Thanks for the replies!

1) No hum or other noise that I can detect but I haven't removed the top of the amp to look (but, following your advice, I will do that tomorrow) and,

2) I leave the system off almost all the time. I only listen on weekends. Would leaving the amp running constantly help?

Keith

Caps can dry out but still work on a 35 year old amp even with little use 

replace caps based on type and age.