I second what Corby says. I have a number of hp 106, starting with one from eBay in 1999. Quite rare. When they work they are somewhere between very good and unbelievable. But most have issues. They are all very old by now and one trouble I've seen is that the double ovens don't work like they used to, which pretty much ruins their performance.

So when you power it up it's a good idea to continuously log frequency (10 s gate is ok) for the first day or two and by looking at the wiggles, slopes, and slope changes, you can tell if the inner and outer oven are working right, or if one is dead, or if due to old age they are fighting each other.

The daily ageing rate should slow down gradually. At some point (maybe months) environmental effects will exceed the ageing rate. These standards were meant to be powered up forever, in laboratory conditions. I had one that was far better than rubidium or cesium short-term, and almost rivaled rubidium long-term. It died of oven failure.

Some photos, warm-up, and long-term plots:

http://leapsecond.com/museum/hp106a/

http://leapsecond.com/museum/hp106b/

If you have questions feel free to ask us on- or off-list. And again, if at all possible collect data from the very first power-up.

/tvb


On 3/21/2020 4:47 PM, cdel...@juno.com wrote:
If whoever bought it needs advice I have repaired a couple of them.

It does not have a dewar.

Both the units I worked on had low to mid parts in 10 -13th from 1 to 100
Sec.

They do take 3 to 4 hours to warm up so don't be impatient.

Aging wont slow down for several weeks.

Cheers,

Corby


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