[time-nuts] Re: HP 5061A oscillator problem

[paul swed]

Morris by all means open it up. You can get to the outer boards pretty
easily. Take pix of the wires. I found a shorted cap that destroyed a
inductor. All replaceable. I know your problems going to be more difficult.
But you can take the oscillator out and power it on the bench.
So pretty easy. Think ground, 21 VDC osc, and 28 VDC for the heaters.
Good luck
Paul
WB8TSL

On Fri, Sep 29, 2023 at 5:05 AM vilgotch1--- via time-nuts <
time-nuts at lists.febo.com> wrote:

>
> H all,
>
> I spoke too soon regarding the crystal oscillator in my 5061A.
> Disconnecting the fast warm-up heater only extended the time before it
> fails. There's obviously a temperature sensitive fault in there. I'll
> either have to try repairing it or find a replacement.
>
> Morris
>
>
> >Hi all,
> >
> >  Since 2006 my in-house frequency standard has been a HP 5061A which
> >still has a good physics package. I have retrofitted a Shera GPS system
> >to it in the disused battery compartment and run it occasionally on the
> >Cs to keep it nice.
> >
> >Recently I turned off all lab power while I was away for a few weeks
> >and when I turned it back on the 5061A wasn't working properly. It
> >would start up and run for a few minutes and then the outputs would
> >disappear. I have traced the problem to the 00105-6013 crystal
> >oscillator unit and I think what is happening is that the rapid warm up
> >thermostat is stuck on. When starting from cold it runs OK until the
> >innards get too hot and then it fails. When I disconnected the AC feed
> >to the rapid warm-up heater the oscillator runs properly and the osc
> >heater meter starts at the extreme right end of the scale before slowly
> >backing off over an hour or so and the oscillator unit feels warm.
> >
> >What I want to know is:
> >
> >1. Is this a reasonable explanation and has anyone seen such a fault
> >before?
> >2. How long does the 00105-6013 take to get to operating temp using
> >it's internal controller  without the rapid warm-up?
> >3. Is the crystal oscillator unit repairable? I suspect a replacement
> >thermostat would be unobtainable.
> >4. Does anyone have a replacement 00105-06013 unit available? To my
> >eternal regret I had a spare and sold it a couple of years ago. It just
> >goes to show you should never throw anything out!
> >
> >Thanks for your help and 73 to all,
> >
> >Morris VK3DOC
> >Melbourne, Australia
> >
> >
> >
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