[time-nuts] Old 500 kHz oscillator

Arthur Dent golgarfrincham at gmail.com
Sat Aug 30 20:22:19 EDT 2014

One of these was my first frequency standard that I used as a marker
for checking the calibration of an old Collins TCS-12 receiver I used
around 1959. I built a small power supply for the oscillator and
used it for a few years until the filament opened and it died. Even
way back then I felt that it was worth saving and set it aside to
repair later.

This past spring I was at the Nearfest ham fleamarket in Deerfield,
New Hampshire and found 2 new oscillators on a table. The seller had
no idea what they were and at the end of the day I bought the 2 of
them for a total of $5, because, like Pete, I just had to have them.
I searched around in one of my many junk boxes and found the original
dead one I had bought over 50 years ago. (I know most of you won’t
find that too strange but my wife thinks my affliction is sad.)

The difference between the original and these 2 that I just bought is
there was a covered access hole to trim the original but the 2 I just
got lack that. Where I had opened the unit up all those years ago I
compared the schematic you show to the circuit of my original and they
do differ slightly. The cover over the crystal oven says ‘Bulova AB-200
crystal oven’ and there is a thermostat (not shown on your) bypassed by
a .01Mfd. The date on the crystal can inside marked ‘VC-1-NL RCA’ is
1/57 so that and my previous experience will help date them.  My original
only has the 1.5-7pf NPO trimmer and uses a fixed cap across the inductor
in the plate circuit.

One of these days I’ll power one up and see how I view its accuracy
compared to my GPSDO.


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