[time-nuts] HP 10811 "salvage"

[Mark Amos]

Some time ago, I complained to the list about an HP 10811 from e-bay that was under frequency (apparently 
it was a non-production unit that somehow made it out of the factory along with a bunch of other somewhat-
less-than-production units.)

I figured it was a lost cause, so I took it apart just to have a look and do some tweaking.  I found that 
I couldn't swing the oscillator enough to get it close to 10MHz.  I thought, OK - it'll be a "parts" 
unit.  

Then I had a brainstorm: since it wasn't working anyway, why not sub out the crystal for one that is 
closer to 10MHz and see what would happen.  So, picking several 10MHz crystals out of my parts box, I 
tried a couple to see how they worked.  I thought I might get lucky and find one with a good temperature 
coefficient and not too much drift.  I thought it was a long shot, but it was dead anyway so no big loss 
if I screwed something up.

The first two xtals I tried were too drifty, but the third one seems to be much more stable.  I've had it 
in fired up for a few hours. The output looks good, and it seems to be staying put at 10MHz (as measured 
by my GPSDO disciplined 5328A.)

Now I know that it won't be as stable as the original fancy SC-cut crystal from HP, but it might be stable 
enough to use as a non-critical bench oscillator for experimenting, etc.  I'll keep it running for a while 
and monitor it's drift just to see if it stays good(or if it dies a smoky death.)

Anyway, I wanted to say thanks to the folks on the list for their encouragement and experimental spirit.  
I siphoned off enough courage from you folks to open up the device and play with it.

Great fun!

Mark