My HP counter has a variation of the 10811
oscillator. To calibrate it, I
bought a 10 MHz rubidium-controlled oscillator
on E-Bay,

What did that cost you? Also how long are the
lamps good for anyway? I imagine they are
expensive to replace.


Leland-

I paid $225 plus shipping for the used rubidium-controlled oscillator. I had
to build a 24 volt DC power supply for it. I have read various articles about
lamp life. It seems that E-Bay sellers will claim that they were designed for
several years of continuous use. The trouble is that you don't know how many
years a second hand unit has already been used! They are most likely being
sold after having been replaced as preventive maintenance. I only run mine
when I need it for calibrating an oscillator. I would expect it to be cheaper
to buy another used rubidium oscillator than to repair the one I have. If it
does go bad, I will look into one of the HP GPS-synchronized oscillators that
are available on E-Bay.

I assume if the thermal fuse is shot the
oscillator won't draw any oven current? I did find
a page that shows how to disassemble the 10811. It
doesn't look all that inviting. Seems the author
of that page had most of his problems dealing with
the sticky tape they use internally. He had by the
way also reported a drifting problem. That's why
he took it apart. But he did say he couldn't find
anything wrong with the unit either.

The oven won't draw current but the oscillator will. An Ohm meter check
between the oven power lead and ground should be relatively low, maybe a few
hundred Ohms?

You DO NOT want to disassemble the oven! All you need to do is remove the end
plate. As I recall, there is a flexible cable near the card-edge connector,
that hides the thermal fuse. The original thermal fuse looked like a tiny
electrolytic capacitor, and plugged into tiny pin-sockets on a circuit board.
The new version looks more like a ceramic quarter or half watt resistor.

If you are interested, I wrote up my experience and E-Mailed it to ARRL's Hints
and Kinks. It was published on Page 68 of the November, 2002, issue of QST.

Please do not take this as a condemnation of the 10811 oscillator. I am very
impressed with how stable it has been over a long period of time.

73, Fred, K4DII