[time-nuts] HP 5061A oscillator problem

[vilgotch1 at gmail.com]

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