Equipment time indicators

[SeanB]

Found i have a pack of these 26VAC 400Hx hour meters still, never used, still in the waxed paper wrapping. Been sitting since 1976, but still likely work. I did have some running as hour meters, using a simple driver, one 555 timer, adjusted to 400Hz, running off 12V, and driving an old 400Hz signal transformer that had windings that would give a 26VAC output on the one set of leads. Capacitor of around 33n on the secondary to sort of filter to a sine wave, and then the clock connected. Ran for over 35000 hours before the clock itself failed, and I never actually replaced it with one of these spare ones.

[BurningTantalum]

They must have been for aviation use.
BT