[time-nuts] 5071A with ATTENTION flashing

Li Ang 379998 at qq.com
Sun Nov 13 10:52:34 EST 2016

Hi Tom
    It looks very clean inside. I think they should be from some lab. There is one with a label CEVA xxxxxx on it. 
    I told him all the information I collected from the serial port. As a reward to travel 200km help him determine the status of these 5071s, he gave me 2 PRS10 rubidium oscillators. 
    I also told him to keep the leaky one running for days and see what's going on. If it goes to normal, price will x2 or more. 

Li Ang

From: "Tom Van Baak"<tvb at LeapSecond.com>
Date: 2016/11/13 19:34:59
To: "Discussion of precise time and frequency measurement"<time-nuts at febo.com>;
Subject: Re: [time-nuts] 5071A with ATTENTION flashing

> Since the ion pump current was dropping slowly.(80uA to 76uA in 1 hour), is it possible to be back to normal?

Hi Li,

Yes, is it possible. Never give up on ion current. Give it hours, give it days if necessary.

Monitor the LCD or syst:print? periodically and plot the trend. The trend may be linear (you may only need to wait for hours). The trend my be logarithmic (you may need to wait for days). If the trend looks like it will eventually drop below 1 uA that is good news. You just have to wait. If the 5071A gives a fatal error and turns off the ion pump for safety, then power cycle to try again.

What you are seeing is not normal behavior. But given the chance that you might get a tube that works, even for a little while, that is worth something. Do you know where these 5071A were installed, or what they were used for?

If it looks like the ion pump current will never drop to 1 uA, even after several days, then you may have a vacuum leak or failed ion pump or too much outgassing or something. Try swapping tubes to see if the new frame shows a similar ion pump reading and trend. If so, then both frames are ok and the tube is bad. I don't know of a fix for this. Cesium tubes fail for many reasons, not just running out of cesium.


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