One of the more frequently asked question is how to drive the aircraft clocks, or chronometer, that can be found on eBay from time to time. The L-1011 had at least two of them, in most cases 3 of them including the clock provided to the second officer. Most of them look somewhat like the one below and most frequently came out of B737s ... just like the one below (A.W. Haydon Company A15580-P1 - Clock, Aircraft Electronic) :
The short answer is that the clocks are not self-contained ... so no simple 28V to two pins and it will run. In other words, they receive their time signal from a central clock source (Master Time Base) ... this very much happens like the old analog clocks you sometimes see in airports or the old clocks you used to have in your school. All these receive the same clock signal so the they all run in "sync" with each other. Below is the standard schematic for a GMT Chronometer made by Haydon:
The schematic is pretty self explanatory with the clock on the right and the Mater Time Base Unit on the right. the Master Time Base Units are somewhat hard to find ... however, they have been on eBay from time to time and this is probably the easiest way to drive the clock ... however, you can also generate your 1V 60Hz signal yourself. Here is the most common pinout:
Pin 1: Instrument Lighting 5VAC (Hi)
Pin 2: Instrument Lighting (Lo)
Pin 3: 28VDC Clock Power
Pin 4: GND
Pin 5: Casing Ground
Pin 6: Clock Signal Phase A (1V)
Pin 7: Clock Signal Phase B (1V)
Pin 8: Remote Switch Output A
Pin 9: Remote Switch Common (Input)
Pin 10: Remote Switch Output B
The phase-shift between pin 6 and pin 7 needs to be 90ยบ for this to work.
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