[time-nuts] HP 5061A - bad cesium beam tube?

[Matt Huszagh]

I received a 5061A that I think probably has a dead tube, but I'd like
to be sure before I give up hope.

I expect the unit has been off for quite a few years, so I first powered
it on with CS OFF. The ion pump reading pretty quickly dropped below 25
and stayed there. I left it like that for about 12h before switching it
to LOOP OPEN. The ionizer, cesium oven, etc cycled on and off in that
state for roughly another 12h before the ion pump reading was low and
stable enough for these circuits to remain on (below a reading of about
25). Once it got to that point the ion pump dropped down to about 20
over a few minutes, where it stayed. I then coarse-tuned the OCXO to
match the frequency of my HP 5061A. Unfortunately, the beam current
indication was only about 2. I waited another 12h. The ion pump reading
had decreased to about 18 and the beam current was still around 2.

Here are all the indicator readings, and the specified normal range in
the manual:

| indicator    | value | normal |
|--------------+-------+--------|
| battery      |    NA |     NA |
| supply       |    40 |  35-45 |
| ion pump I   |    18 |   0-15 |
| osc oven     |    39 |  20-45 |
| cs oven      |    14 |   5-35 |
| 5 MHz        |    37 |  35-45 |
| mult         |    42 |  35-45 |
| beam I       |     2 |  15-30 |
| control      |    -2 |        |
| 2nd harmonic |    15 |  20-45 |
| 1 MHz        |    37 |  35-45 |
| 100 kHz      |    37 |  25-45 |

I measured the +3500V supply as +3.2kV with it still powering the
beam. That's within the >+3kV spec.

The ion pump reading is still above the 15 spec. Should I leave it on
for a couple days to see if that comes down? The manual does say this
could take a few days to be in line. The extremely low beam current
reading concerns me, however. I haven't touched the BEAM I METER pot
yet, so I don't know how that's set.

Anything else I should do?

Thanks
Matt