[time-nuts] Adding adjustment pot to 5680

[paul swed]

Arthur,
Nice pixs well lit with good detail. If only I had spent some time digging
around that would have been much easier to solder to. May change it the
next time I am in the unit.
I do agree that the reg was running pretty hard but you attached it to at
least a 115 degree heat sink. (At least in open air with real attached heat
sinks)
I am unsure as to what I will do. Clearly I have the 7805 on an external
heatsink. Nice and cool. I ran the wires through the pot hole to a cheap
bournes 10K 10 turn pot.
Since my plan is not for portable operation but a rack mounted device I
will use a very stable external regulator and at 3.3 or 5 V then a very
good 10 turn .1% linear 10K with numeric readout counter. Flea market
special.

Sort of scratch my head. I like the larger external heatsinks I was using
and the fact that they kept that center rail at 115 degrees should extend
the life of the electronics even though the RB ref tube is the real life
limit.

I think the only comment I have read is that someone added a heatsink for
thermal mass stability. Lots of pondering on my part.
Last check Ref at 8.26 E-12. I am noticing 500 ps semi regular phase jumps.
Fact is it could be my other even older lucent RB. Time to get serious with
the HP 5065 and the z3801. Who is fibbing to me??

Regards
Paul

On Sun, Jan 15, 2012 at 1:31 PM, Arthur Dent <golgarfrincham at yahoo.com>wrote:

> >paul swed:
> >"Hardest part is attaching the 100K resistor to the ic. Boy thats small."
>
> I didn't solder the resistor directly to pin 5 of the IC. I found that pin
> 5
> was connected to a nearby SMD capacitor that was a little easier to
> solder to. Attached is a photo of the correct location if you want to try
> bringing the EFC out for analog control.
> http://farm8.staticflickr.com/7170/6702435071_f684967719_b.jpg
>
>
> Where others had commented that the internal 7805 I added was running
> without a heatsink and would be close to max ratings, I started to worry
> and
> decided to mounted it on the heatsink that runs down the middle of the
> 5680A using an existing mounting hole that is used to mount a TO-220
> device on the other side. The screw used to mount that device is too long
> so I replaced that screw with one that doesn't go quite 1/2 way through the
> heatsink and used an identical screw to mount the 7805 on the connector
> side of the heat sink.  I had to elongate the mounting hole in the 7805 so
> it
> Wouldn’t interfere with the cover or the dimple in the cover where the
> screw
> that holds the cover on screws into the heatsink.  The photo linked below
> shows the better way to mount the 7805 so you can use a single 15V supply
> for the 5680A.
> http://farm8.staticflickr.com/7157/6702428471_5a7b96068d_b.jpg
>
> -Arthur
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