@ccogopher Make that service sooner rather than later. You really don't want to find out what happens when the power transformer burns up. This is something that can happen to any amplifier that old with original filter capacitors in the power supply!
Since they are that old, its a guarantee that you're really not hearing the amp at its best. If you like this amp, get this done right away; don't use it until this is done- replacement power transformers are rare and expensive.