[time-nuts] HP5061B Ion Current

[Pete Lancashire]

Do a search of the list and a few other sites. there is a LOT of
information on what challenges one can have.
And a lot of the information is practical.

As for as pumping a tube down, it took me pretty much a day + a whole
weekend, but it did go down to what was
scribbled on the door, and now takes less than a minute. I only turned mine
on either once every 2-3 months or when
I wanted to use it. Before the current issue of what looks like a power
supply going nuts, I got lock in no more that
203 minutes. If I was not going to use it, I would let it run for 30-45
minutes and shut it down for the next 'pump down'

-pete



On Mon, Mar 20, 2017 at 4:44 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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