[time-nuts] HP5065A S/N 0048-00131 - Worth repairing (and how to do it)?

Magnus Danielson magnus at rubidium.dyndns.org
Sat May 6 18:29:08 EDT 2017

Hej Ulf,

Having repaired and trimmed a few HP5065As, I'd say it is worth the 
trouble. I have not encountered this specific fault thought.

Magnus SA0MAD

On 05/06/2017 11:49 AM, Ulf Kylenfall via time-nuts wrote:
>  HP 5065A S/N 0048-00131
> Repairing the heater...
> I was able to get my hand on a faulty 5065A
> that was left for dead.
> The date codes on the semiconductors says 1968
> so this unit is 50 years old... This instrument
> has some provenance as it was
> used in the European end during the very first
> trans-atlantic VLBI (Radio Astronomy)
> experiments between Sweden and the USA.
> The unit has the known problem with one of the
> rubidium unit (s/n 05065-6001)
> heater wires shorted to GND.
> This failure was the cause of the decomissioning.
> I managed to salvage:The transmitter lamp (fires up within seconds when connecting it to a 20V DC source),The Rubidium glass cavity, The photo-cell at the receiving end.
> Having downloaded the "First-aid" documents
> from KO4BB, I read a quote from Corby Dowson
> regarding this problem and what to do about it.
> I have been able to separate the TX/Rb/Rx assembly from
> the magnetic shields but after this, I hesitate
> about how to proceed. (why did not HP put more energy
> in trying to isolate the magnetic winding from the shield?
> Any scratch on the enameled copper wire and a short
> circuit will be the result here as well?)
> As far as I can see, the magnetic
> winding has to come off. The rest of the
> polyurethane (?) structure has to be removed
> after which that structure has to be rebuilt
> using some other material (PTFE?).
> One other reason why I hesitate is that this unit is
> v e r y old. It uses regenerative dividers
> instead of binary (etc) and a lot of other
> obsolete components.
> I could use some suggestions about what to do next.
> One other question is of course if it is worth
> putting a lot of energy trying to repair
> a 5065 as old as this. Perhaps easier to go
> look for a working modern 5065A on the open market?
> Comments invited.
> Ulf Kylenfall
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