[time-nuts] HP 5061A Problem

Adrian rfnuts at arcor.de
Sat Sep 21 08:27:38 EDT 2013


I got a 5061A with high performance tube that I'm trying to get running.

The Cs oven works and the -3500 and -2500V are there.
The beam current has its maximum at the correct frequency.
90MHz from the multiplier are there and they are phase modulated with 
137Hz at about 0.01 rad.
Measured on a spectrum analyzer, the 137Hz sidebands are some -47dBc.
I'm not sure if that low modulaion index is correct though.

Also, the harmonic generator alignment worked as described in the manual.
Measured with the EM output into a 10M input DMM, the floor was around 
-60mV, finally set to some -90mV after alignment.
The low frequency test worked as well and delivered a maximum at some 
41.6kHz.

An unusual observation is that the meter indicates beam current 
immediately after switching the CBT on.
Nevertheless, it could be tuned to the correct maximum after warming up.
However, there is still no 2nd harmonic and it doesn't lock.

Measured with a scope directly at the EM output, there is mainly noise 
with just a faint signal when maxed with the A3 mod level potentiometer.

Unfortunately, I couldn't find reference data in the manual, neither for 
the beam current nor the multiplier modulation index.

So far, everything seems to work properly except for the missing 2nd 
harmonic and the unusual beam curren behavior.

Any help would be much appreciated.

Adrian


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