[time-nuts] HP5061B Ion Current

Donald E. Pauly trojancowboy at gmail.com
Mon Mar 20 19:44:49 EDT 2017

This is my first post.  I just bought a non-working HP5061B on eBay
for $350.  My old boss KB7APQ in Salt Lake City and I are working on
it.  It came in from the Philipines in October of 2015 and was
diagnosed with a bad physics package in March 2016 by AllTest in New
Jersey.  We initially found an open R8 pot on the 5 mc oscillator
A10A2 which was killing most of the output.

Next we had ion current of about 25 uA which stayed up.  The book
seems to indicate that this was low enough to enable the cesium oven.
The analysis of the theoretical ion current for cesium turn on was
very difficult.  We shorted the base emitter of Q6 on A15 board to
override Cesium oven disable. The instrument then achieved lock with
beam current of 20.  Ion current rose to 35 after cesium oven warm up
and lock.

We have made great progress on the +3500V power supply analysis.  We
believe that many so called gassy tubes are perfectly functional up to
1 mA ion current.  Mean free path is on the order of 142 mm in that
case or the length of the beam.  We will discuss our findings if there
is interest.

WB4BBP has been most helpful with our efforts.

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