[time-nuts] HP5061B Ion Current

[paul swed]

Donald welcome to the group. If a units been off a long time and it sure
sounds like thats the case it may take quite a while like a month or so for
the unit to remove all of the "Stuff" that has out gassed. So be patient
and let the pump do its job. After it does lower and my fingers are
crossed. Then you only need to run it about every 6 months.
The fact that it actually locks and you found a simple fix is pretty good.
What was the beam current?? That gives you a hint on the quality of the
tube.

Not sure I would run the defeat on the HV supply for to long. That may
stress the supply if I had to guess.
Regards
Paul
WB8TSL

On Mon, Mar 20, 2017 at 7:44 PM, Donald E. Pauly <trojancowboy at gmail.com>
wrote:

> 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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