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

[paul swed]

Matt well written up comments on what you are seeing.
All is not lost. Let it run. Frankenstein takes some 48 hours to lock when
I first was able to make it work.
Now over several years it locks in under 2 hours.
Beam = 0 and its not broken.
Its interesting that your offset is -2 that may be a good sign that its
actually trying to lock or is locked.
Especially if its staying at that offset.
The fact that the multiplier is 42 really appears a good sign.
OK fact. Those lamps go flat on the center bottom contact over years. Are
you sure the green lamp is good. Swap it with the yellow if you know the
yellow is good. If thats the issue a drop of solder fixes the center
contact.

If all is working you have a low beam tube. So its going to have a lower
signal to noise. But it will hang around the right frequency. This is
getting picky because if I didn't have other CS to check I wouldn't know
honestly.
Regards
Paul
WB8TSL

On Sat, Feb 25, 2023 at 11:25 AM Matt Huszagh via time-nuts <
time-nuts at lists.febo.com> wrote:

> 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
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