I use to help a guy balance engines. He had an old Stewart Warner balancing
machine that had tubes in it. One day while shutting down I noticed the
machine was on so I shut it off. Next day we came in an he noticed it was
off, and I told him I shut it off. Boy, he said , you just killed it. Sure
enough, thing wouldn't work. As long as the machine stayed on everything
worked, shut it off and the tubes would go bye-bye. Sent it back to Stewart
Warner and they dusted off an old retire E and we'd get it back in two or
three weeks. Thing would crap out in power failures to, sometimes.
Dam good machine. Pick up the slightest imbalance.