[time-nuts] Re: HP5061 offline management.

[Andy Talbot]

I have a 5061A that has been sitting in my shack for over 25 years.   I
keep it in  standby, using just the OCXO as a casual reference, good for
less than 1 PPM.  I check the 1PPS output against GPS using a counter timer
and tweak the front panel pot a few times a year to keep it spot on.
When high accuracy is needed, perhaps a few times a year, Cs is activated
and it typically comes up to satisfactory accuracy is around an hour - I
usually leave it two hours.

Yes it consumes a few tens of watts, but I'm quite prepared to spend the
few pence per day that costs :-) to keep the tube fully pumped and ready to
go.

I replaced the NiCd battery pack which was completely dead when I got the
unit with a LM317 and float charged 24V lead acid batteries.

Andy
www.g4jnt.com



On Thu, 5 Aug 2021 at 23:26, paul swed <paulswedb at gmail.com> wrote:

> Was talking with another time-nut on the best way to use the HP5061 Cesium
> to protect the tube. I have read over the years that some people let the
> system run but with the CS oven off.
> This consumes 19.4 watts or about 14KWH/month.
> But has the advantage of a nice local reference and the tube is pumped
> down.
> I however leave my units completely off and run them every 2 months. The
> downside of this is that when the ion pump clears the tube when the CS oven
> is turned on there is a crud burst and the ion current reading can go
> significantly up. Then has to pump back down a number of times.
> There is a better way.
> Leave just the 3500V supply run. Disconnect it from the internal power add
> a resistor and cap powered by a external switching wallwort in the 1 watt
> range. Brand new meanwell  units are $11. These are medical grade not that
> its required. The resistor is about 470 ohms a 1/4 watt. Dropping 24V to
> 19V. Use a 470 uf cap on the side of the resistor connected to the 3500V
> supply. Ground the negative to the chassis so the I pump meter works.
> Taking this approach drops power consumption to .31 Watts. Larger higher
> current supplies will draw higher power wasting idle currents.
> I was going to drill out a hole and mount a small powerjax. But just really
> didn't so brought out a pigtail to a powerjax. No change to the chassis.
>
> Operating this way the 3500V supply is always running. When I want the CS
> to run I plug the original power cord in. After the ovens warm up in
> business. No waiting for the ion pump to do its job and the best benefit No
> crud burst as the tube is clean.
>
> The same adapter will easily power many 3500 V supplies. I have 3 5061s
> that will be modified. Good news each 5061 consumes about 10 ma.
>
> Lastly 5061s do make noise around 2 KHz somewhat annoying.
> Its easy enough to use a wall time and run just at night and switch the
> supply on when actually using the Cesium. But a timer just multiplied power
> consumption a lot.
> A greener HP 5061.... Did I just say that. Sorry.
> Regards
> Paul
> WB8TSL
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