How to restart tube amp and pre in boxes for 2yrs

It’s always a good idea to use a Kill-A-Watt energy monitor (available on eBay or Amazon for $20-$30) in series with the Variac to monitor the current draw of the amp as the voltage is slowly brought up.  If everything seems fine at first, I always leave the Kill-A-Watt hooked up for a few hours while running the amp to make sure current draw doesn’t start creeping up which usually indicates a power supply cap about to give it up.

Yes, a device to monitor voltage and current draw of the amp is the best approach.  I've seen situations where even at a low voltage setting when powering up, the current draw appears too high so one knows there is a problem somewhere when well below when full voltage is applied.  Measuring current and voltage together is the best approach.  Interestingly, a very young tech I know said that he actually prefers a dim bulb to relying on the ammeter.  He said that the bulb reacts faster than a readout of current.

That's all good to know.  In '17 I powered up a tube amp of mine that had been dormant for nearly ten years and in '20 I powered up another tube amp I owned that had been in hibernation for well over ten years and i wasn't aware of this stuff so I basically plugged them in and turned them on. 

I guess I was lucky.

That second amp I alluded to has been asleep again for about four years so I guess I should look for a variac on ebay.  The second amp, the one that woke up in '20 and then went to sleep again, does use a tube rectifier though.