On 2021-02-28 5:53 PM, Dan Kemppainen wrote:
Hi All,
I've picked up a couple of old crystals. Mostly because they look neat.
They are 1Mhz, in a glass tube. The quartz is ~25mm dia, at about 1 mm
thick. Was able to get them to oscillate using a Colpitts circuit. They
will oscillate at 2.851Mhz (probably some strange mode) if given the
chance.
I've been scouring my reference books here, and haven't had much luck
finding any details on how one would even guess at the parameters of a
quartz like this.
There area few numbers on them, 33 stamped on the side, 1000 (KHz???) on
the top, 87 on the top, and hand written 501 (probably a SN). Digging on
line, I'd guess an AT cut based on thickness. I'm guessing the 33 is
capacitance in pF. 87, might be year.
If any of you have any suggestions on where to find information on how
to get something like this to oscillate properly, guess at correct
parameters, or even measure any of the parameters I would really
appreciate it.
I'm sure these are really nothing special, but it would be neat to give
them a fighting chance to show what they can or can't do without
breaking them!
Those are available from at least a couple of Ukrainian ebay sellers.
Search for "1000 khz". There's also one that comes complete with the
oven assembly: https://www.ebay.ca/itm/254748662460 . I picked up a few
of the bare crystals to help me understand the oscillator circuit in my
HP 104AR frequency reference. I breadboarded a circuit that was similar
to the 104AR (i.e. similar to the HP 103AR) and with a couple of circuit
changes the crystal worked properly. I changed the transistor from
Germanium to Silicon and changed C105 from 30nf to 3nf. Note that you
*MUST* build the AGC circuit or you'll probably destroy the crystal by
overdriving it. Play with the base bias voltage to get the circuit to
oscillate.
I used a Saunders 100HF meter to measure the crystal parameters, but I
don't understand the results. Cm = 16 ff and Lm = 1.6 H which are
fine. But Rs < 1 ohm?? Other crystals measured using the same
technique gave me results in the tens or hundreds of ohms. But all four
of these crystals measured < 1 ohm.
I haven't done any temperature testing on them.
Ed
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