[time-nuts] 5061A Problem Child

J. L. Trantham jltran at att.net
Sat Jun 12 03:49:53 UTC 2010

I have a 5061A that appears to be working correctly except there is no 2nd
Harmonic indication.  In addition, on the A7 assembly, there is no sine wave
out on J2.  When looking at the cable from the tube to J1, there is no sine
wave there either.  However, the Beam I indication is appropriate and I have
been through the alignment of the Harmonic generator assembly, the electron
multiplier to match the voltage on the tube (which is a high performance
tube), the C-Field adjustment, and the modulation frequency adjustment.  I
have also swapped the A7 assemblies and the A3 assembly with known good
units.  All to no avail.

The Beam I moves down with Mod On which implies the tube is being modulated.
The 2nd Harmonic indication moves when you turn the Loop Gain pot up and
down but no steady indication of 2nd Harmonic.

I have compared measurements from a working 5061A with the problem child and
the findings on the A7 assembly seem to be the only notable differences.

I can't think of an explanation for why there would be Beam I but no 2nd
Harmonic given the above findings.

Anyone with any ideas.

Thanks in advance.


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