Firing up old tube amps. Should I worry?

This is the P/P EL34 type tube amp.

Electrolytic capacitors deform over time when not exposed to voltage. The oxide layer that forms the dielectric slowly dissolves. Capacitors that wee rated at 450 working volts when new might only be able to handle a fraction of that after 15 years unused.

It is also possible for the electrolytic capacitors to dry out over time.

Best advice is to inspect them for bulges or leaks, then use a variac to raise the voltage slowly and give the capacitors time to re-form.

Buy a cheap pair of speakers from Best Buy, stand back, put some safety glasses on, flip the switch and use the return policy.

why Best Buy you can buy used car speakers from autowreck yard for $4 pair and connect them.

Marlin38,

How about pulling the signal and power tubes.

If the rectifier is a tube you will need to leave it in.

If you are worried about powering them directly off the mains put some kind of load in series with an amp first.

The wife's toaster or maybe an iron. Something with around 500 watts resistive load.

Fire it up, sorry couldn't resist, and check power supply dc output voltage. Leave it on for a minute or two.

If no smoke plug the amp directly into the wall recept.
Check power supply DC voltage.

If everything looks OK unplug amp install tubes.

A couple of cheap speakers might not be a bad idea for the ultimate test.
.