Use a Variac and it will last 1000 years probably. I use one on all my older Macs. 100-110vac they work perfect.. The pair I use them on is 1965-69 model MC225 and MX110z. Other than an ECC83 (12AX7) a couple of times. The original Telefunken valves are still in them both with GE Mcintosh power valves.
120vac they would have blown the PS or something up years ago.
I have figured out a lot of things with a Variac to. Mostly how to quiet a transformer down and play late night with ZERO floor noise.
I like it when the wife messes with it. NO you have to hold that and turn that up..
I love messin' with her, Hair stickin' straight UP.
Time to feed the chickens..
Regards