[time-nuts] HP5065a cfield issue

[Bob kb8tq]

Hi

The C field coil resistance is low enough that you have something in the vicinity
of 10mv across it. If you want to check the C field regulator, I’d just pop a wire and 
put a meter in series with the coil. 

My bet: your synthesizer has slipped a bit somewhere. I’d check it’s output
against the table in the manual to make sure it’s still on frequency before I dove
into the C field. If it’s off, the switches would be my first target. Rotate them a bit
to wipe off the contacts and see if the frequency is correct when you reset them
to the original position. 

If none of that works, I’d be happy to give your 5065 a new home :)

Bob

> On Nov 30, 2020, at 6:57 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> Hello to the group.
> Was time for the quarterly Cesium and RB checks in an effort to support our
> local power company.
> I discovered that there is an issue with the HP5065a Rubidium reference.
> 
> The frequency has slowed and the cfield pot can not make up for the jump.
> Normally a few small tick marks are ever needed. I used 3 large marks and
> ran out of pot. Its at 9.9. Was at 6.14. The frequency does increate with
> the cfield adjustment. I am assuming perhaps something has happened in the
> cfield regulator.
> At least the front panel meter is indicating the +20V supply is normal.
> But my question is this. The schematic indicate very little current travels
> through the cfield coil. Guessing far less than 3 ma. by adding up
> resistors. What I do not know yet is what is the resistance of the cfield
> coil? I may find that I simply have dirty contacts on the A15 regulator
> card.
> Its possible there are other things wrong but all front panel meter
> readings look the same as they have been for years.
> 
> Thoughts?
> Thank you in advance.
> Paul
> WB8TSL
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