[time-nuts] O-451A/u 5 MHz oscillator: more photos

Eric Scace eric at scace.org
Wed Jun 8 13:58:53 EDT 2016

   I added some more photos of the O-451A/U to a Dropbox folder <https://www.dropbox.com/sh/ly4632gydad1o0v/AAASa3Yw-wXOp6GEsAcdSZJRa?dl=0>. There are no obvious manufacturer marks beyond the Western Electric contractor cited on the Coast Guard nameplate on the front panel. Note that the large electrolytic cap and transformer are a quick & dirty mod to bypass the dynamotor in the supply.

   In opening the rear of the unit to compare with the photos Corby sent on Jun 2nd, the dynamotor prevented me from removing the insulation plug in the back. But the guts in the front of the unit are identical (other than my father thoughtfully added a spare tube inside when he was working on it).

   The O-451A/U puts out 5, 1 and 0.1 MHz square wave… implying a 5 MHz crystal inside the double oven. The rear panel photo includes a marking that describes the crystal as a GA-10752.

   As mentioned in an earlier email, these oscillators appear to have been used in Loran A/B transmitter sites. The last in-service date shown on the inside of the dropdown front panel for this particular unit (serial #11) is 1974. If there was a separate calibration logbook, it was lost when the unit was declared surplus.

— Eric

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