Blown Cap???What Else To Replace During Service???

The amp is 20 years old & ran Class A HOT

@freediver Electrolytic caps don't like heat so 20 years does make them suspect.

Look for burned areas on the circuit board, as well as burned-looking resistors. If a capacitor shorts out, it will often take other components with it.

Transistors can fail in milliseconds with no visible external signs. They will need to be tested for shorts and open circuits.

The amp is 20 years old & ran Class A HOT so I figure some components must have been affected.I hope it's just something simple like a cap..

Agreed with Ralph and the others on replacing electrolytics after a given age. I have had many successes with my gear with a magnifying class looking at caps for signs of heat, puffiness, or juice leaking out. Since I have a soldering iron and mouser account, I simply replace all the caps if one fails--not very expensive for me. I guess 20-30 years. My limited experience is that mouser and digi key are superb but mouser seems to stock more of the older type caps used by older devices.

How old is this amp? If over 20 years, filter caps might be a good idea. If only 10 years, unless poor quality parts were used initially, the caps should still be good. Usually a 'pop' and failure is something other than a capacitor failing...

     ANY electrolytic caps in the amp are subject to drying out with age.

                   Not just those in the power supply.

     Have all replaced and save yourself further headaches.

The big item on amps that needs to be thought about are all the power supply caps. That's what will wear after 20 years or longer (depending on when made, new amps have better caps).  Power supply caps can go and cause a cascade of failures which can end up turning an amp into a brick.

So, if your amp is reaching that age, recapping is good.  The other parts are going to be much more reliable.

This is my end game amplifier so I really would like to have it gone through & brought up to as new condition.Aren't there any systems or components that usually follow bad caps that can be at least checked for condition?Thanks very much all.

Just have it repaired.  There is no good way to predict ahead of time what will go next.