Indeed Andy that is what numbers of time-nuts do with the 5061 as I mentioned in the post. But for those of us reducing power consumption I offer a way to do that with pretty minimal effort. I work with a fellow that has 2 5061s that bell labs in NJ throughout many years ago. (So will guess the tubes are dead) He is a ham and like you uses the OCXO. The CS has actually never been turned on. He doesn't know how. That was quite a surprise. It lives in his barn no less. So most likely we will make a run at actually firing it up. Regards Paul WB8TSL
On Fri, Aug 6, 2021 at 9:24 AM Andy Talbot <[email protected]> wrote: > 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 <[email protected]> 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 > > _______________________________________________ > > time-nuts mailing list -- [email protected] -- To unsubscribe > send > > an email to [email protected] > > To unsubscribe, go to and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send > an email to [email protected] > To unsubscribe, go to and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
