[time-nuts] HP5065A C-field mods and optical unit mods

cdelect at juno.com cdelect at juno.com
Fri Nov 17 15:37:57 EST 2017


The TX and choke and filter caps were removed as I had envisioned I would
have to re-mount the A1 and A7 in their location.
However with some judicious movement of the mounting holes I was able to
squeeze them in close
to their original spots.

The 5065 chassis was removed and inserted into a chassis from an HP
8405A. (just used the side panels
and the rear panel.)

I'll post a schematic of the new C-field supply next week. It consists of
two LM299AH in series feeding
a string consisting of a 2.4K, 1k, 1K and a 1K low TC pot. A switch
allows you to short out one or both of the 1K resistors as a coarse
adjustment. All resistor are 1PPM.

Fixing the 20Volt and the C-field temperature contributions allowed me to
isolate the optical units changes 
due to temp.

The resistor thermistor combo I mentioned would be taped to the optical
unit and compensate it only.
It would be in series with the C-field coil.
Not needed in my unit but thought that others might want to try it rather
than getting as complex as I have.

Yes the active baro and temp circuit would be an alternative for a unit
without my mods.

attached are PIX of the enclosed optical unit and the front panel.


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