[time-nuts] High Voltage lead on HP Cesium Tubes

paul swed paulswedb at gmail.com
Mon Jul 12 11:40:52 EDT 2010


Great question.
I noticed the same on my dead unit. That indeed may be why I had to readjust
the 3500 supply as I recall.

On Sun, Jul 11, 2010 at 11:32 PM, J. L. Trantham <jltran at att.net> wrote:

> Has anyone ever replaced a high voltage lead on an HP Cesium tube?
>
> I have a 5061A that required prolonged pumping at +6000 VDC to get the Ion
> Pump current to go down enough to allow the unit to turn on the CS Oven but
> then would slowly increase to the point that it would again not let the CS
> Oven turn on.
>
> At +6000 VDC, the current would be about 1400 uA but only about 30 uA at
> +4000 VDC.  It got me to thinking that there was some sort of HV breakdown
> going on.  On inspecting the tube and HV lead more carefully, I found the
> +3500 VDC lead cracked and considerable 'soot' on the silicone 'cap' on the
> tube where the red HV lead entered the tube.  I removed the connector,
> cleaned the wire and silicone cap, separated the silicone from the lead and
> slid some heat shrink tubing over the wire and into the silicone cap.  I
> used the heat gun to shrink it in place then placed another layer on this.
>
> Now, the tube seems to work OK (at least observing it for about 48 hours)
> with the Ion Pump I stable at about 6 and with no increase, a distinct
> change and improvement from before.
>
> Perhaps I should be satisfied with what I have got but I was wondering what
> is under the silicone caps and how to go about removing them to replace the
> +3500 VDC and -2500 VDC leads.
>
> Does anyone have any experience with this?
>
> Thanks in advance.
>
> Joe
>
>
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