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

[paul swed]

The shipping is going to be nasty but then you have dealt with that already.
Frankenstein's beam is 0 and it was a bad tube given to me. The original
was a option 004 and it was totally dead.
It gets tricky if you have a RB and the CS. Who is right? If you have a
gpsdo thats very helpful in understanding which one may be drifting.
Frankenstein's beam has always been 0. But the 2nd harmonic is 32. I
actually inserted an amplifier in the beam measuring circuit and could read
the beam current or leakage. Who knows it was very small and did seem to
peak. But it does lock and doesn't seem to drift with respect to the other
Cs. I use a GPSDO to set the 5 MHz. Eliminates the whole double peak
possible issue.
Depending on how much you paid. It could be a keeper. Frankenstein was $125
at a flea market. But the lessons I learned from it have been far more
valuable/fun.
Regards
Paul
WB8TSL

On Sat, Feb 25, 2023 at 2:56 PM Matt Huszagh <huszaghmatt at gmail.com> wrote:

> Chris and Paul, thanks for the notes.
>
> It now locks! It wouldn't last night, but I just tried again and the
> continuous operation lamp illuminated. Unfortunately, the beam current
> is now close to 0 and the 2nd harmonic is at about 10.
>
> The 5 MHz signal seems pretty stable relative to the one from my
> 5065A. It drifts a little back and forth, but not much. I expect this is
> a symptom of having a low SNR.
>
> Chris, I do have the service manual; I'll take a look at the loop gain
> adjustment and the -2500V supply.
>
> Still, I'm not thrilled about having a unit with a weak tube. The seller
> claimed this functioned correctly (from the pictures though I don't
> think they knew how to test it). If I can get a good discount I'd keep
> it, but otherwise I may send it back.
>
> Matt
>