[time-nuts] New life for old Tracor rubidiums

[Skip Withrow]

Hello time-nuts,

A while back I acquired a Tracor 308A (ATT version with 4.94MHz output
also) in the hopes of comparing it to the HP5065A and perhaps using it
to experiment to improve stability.  The two units are the same form
factor, use similar sized optical units, have similar electronics, and
manuals with schematics are available.

Tracor's are notorious for lamp failures (underfilled lamps).
However, the lamp on this one did light although it did look a little
funky.   Try as I might, I just could not get signal through the
optical unit.

So, I ended up acquiring a similar Tracor 304D unit with the hope of
swapping parts and comparing to get one or both working.  The lamp in
this unit was dead and would not even light.

So, I ended up yanking out the lamp assembly and replacing it with one
from an FEI FE-5650A (with appropriate mechanical adaptations).  After
a little alignment it worked like a champ.  Next I took the new lamp
assembly and threw it in the 308D.  And that worked like a champ.  So
a second new lamp assembly was built up (I have a pile of dead 5650A
units).

The moral of the story is don't throw out those old Tracor units.  I
have not run stability tests yet, or attempted any improvements but
they make great experiment test beds.  I have attached a couple of
pictures of the new optical unit and its installation and the two
units chugging along and happily locked up.

Regards,
Skip Withrow
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