[time-nuts] 4040A question

[Bill Hawkins]

As long as we are discussing fine old FTS Cs standards, I have
a question about the 4040A. I have no manual and no hope of
finding one. I have an operators manual for the 4040B that
mostly discusses the RS-232 command set. My 4040A has no pins
in the RS-232 connector.

I opened it up to see what I could see, and saw a black spot
on one of the circuit boards. It was caused by an overheating
3 ohm 1/8 watt precision resistor in the collector supply for
the hot wire power supply. The resistor still measured 3 ohms,
but I replaced it with a 2.7 ohm 1/2 watt film resistor mounted
1/4 inch above the board. No harm seems to have been done.

I found just two adjustable resistors on circuit boards and one
potentiometer mounted so that it was adjustable with the unit
closed up, on the lower right side. This is near the OXCO (I
assume from its connections). Before I tweak that adjustment, I'd
like to know whether it trims the OXCO or the C field. There is
a drift of about 100 nS in 12 hours referenced to an HP Z3801A.
I really don't want to tear up a working unit to trace the wiring.

Any leads on a manual appreciated, as are any comments on the
usefulness of the 4040A.

Regards,
Bill Hawkins