[time-nuts] 5062C

[John Miles]

> There's an HP 5062C closing on eBay soon!
>
> Corby
>

Thanks for the heads-up, Corby, even if it incited a bidding war. :)  I
bought it and got it working without much trouble.  The problem turned out
to be a resistor that had drifted high and crowbarred the oven-temp shutdown
circuit.

Its cesium tube is elderly but still has some life in it.  Beam current is
about 0.47V at the test point (or 10 on the front-panel meter) with the
mass-spec voltage at the first peak of 12.0V, and about 0.68V (~12 on the
meter) with the mass-spec voltage at its highest peak, at 17.5V.

Question: the 5062C manual has some contradictory instructions for setting
the mass-spectrometer bias.  Page 4-45 says the adjustment is "correct" when
the beam current is at its lowest-voltage peak.  Page 4-56 says "More than
one peak may be indicated... Set MASS SPEC control for highest peak."  Which
is optimal?  In my case I see a lot more beam current at the 17.5V peak than
at the 12.0V peak, so I'd rather leave it at 17.5.

The bad news is that when I tried installing my spare 5062C Cs tube, which
I'd previously bench-tested successfully, the hot-wire ionizer filament
opened up at some point during the periodic supply-cycling process that
takes place until the ion pump current falls to its normal operating value.
That sucked, because now I'll never know how the bench test results compare
to actual performance in the clock.

I don't see anything I might've done wrong when I installed the other tube.
There was just too much O2 in the envelope, I guess...

-- john, KE5FX