[time-nuts] Adding adjustment pot to 5680

paul swed paulswedb at gmail.com
Sun Jan 15 01:32:04 UTC 2012


Just did the pot addition to my FE5086 and it works very well
The systems still warming up and its actually apart with external heat
sinks for cooling so I can get to places.
Hitting 8.6 ^ -12 after first eyeball adjustment on the scope drifting 5 ns
in 9:36 minutes. Time to flip from scope mode to 5371 counter ns drift
timing so I don't have to stick around.
Hardest part is attaching the 100K resistor to the ic. Boy thats small.
I plan to bring the leads out through the fake pot hole to a nice 10 turn
pot for control. I also have counters for the pots.

I also do not have the 1 pps out. Not that it matters to me actually. I did
probe around looking just for the heck of it and no luck.

Further updates
Created a excel drift calculator for use with readouts from 5371 counter.
Final setting so far 4.76E-12.
Clearly on my unit the pot I am using could be better and I need to adjust
the range for about 0-3vdc. Had been using the 8 V regulated supply.
Thanks David and Arthur for the thread and mod.
Regards
Paul
WB8TSL

On Thu, Jan 12, 2012 at 7:05 AM, Arthur Dent <golgarfrincham at yahoo.com>wrote:

> >Look forward doing other tests like voltage sensitivity and bringing
> >out the C field for external adjustment.
> >EWKehren at aol.com
> ++++++++++++++
> >But how do you adjust the RgO output frequency?  That's why I asked if
> >A DDS would be used.
>
> >Nevermind.  I just found it.  The RgO cell can be frequency adjusted
> >magnetically.
> >David
> +++++++++++++
> I decribed the very simple way I added an external EFC feature to my 5680A
> unit using a pin in the DB-9 connector that was freed-up after I installed
> an
> internal +5V regulator inside the 5680A so I only needed a single +15V
> supply to power the 5680A. Check my post of Mon Jan 9 21:06:12 UTC 2012
> to see what I did using Bill Riches information where he described
> connected
> an internal pot. The new EFC pin 'floats' at 2.5V and 0-5V works fine to
> adjust
> the frequency slightly.
>
> -Arthur
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