[Milsurplus] BC-221-AK Looking for DC9 metal can 1000Khz

[John Hutchins]

Pete -
Thanks for the feed back.  Yep read all that -; 1Meg resistor was 
replaced with a 1% carbon film; the old carbon comp was @1.3 meg. just a 
tad high.  The Black tubular ceramic capacitor marked 6pf passed a 25V 
leakage check and was dead nuts at 6pF.  The crystal however is in a 
black Mil. Metal Tube type can; BUT with 6 screws on the bottom, a 
rubber gasket and a retaining ring.  I suspect that the seal was some 
how was compromised or the internals are in need of a good cleaning and 
adjusting.

At the moment I want to put that project off and get a replacement DC-9 
1000Khz crystal in a "sealed" can, no screws/retaining ring, and test 
out the circuit which I suspect is functioning correctly.

Note: Early on these crystals were made in the open-able can's;  As the 
designers and manufactures got smarter the newer models were sealed up 
in the Metal tube case with no screws.  A lot of crystal research was 
performed during the war to compensate for aging, environmental effects, 
and packaging methods. 

Just a thought I wonder if the newer DC-9 crystals of that time were 
filled with a inert gas or just a simple vacuum?

Curiosity got the Cat last night:
Removed the retaining ring, Can would not separate from the rubber seal 
with a gentle twist.  Soaked the "Crystal in a can" with ATF to soften 
the rubber seal, using my thumb to gently pull up the rubber seal 
edges.  After 2 hours of soaking and thumb-ing the can would not 
separate from the rubber seal.  Set oven at the lowest temperature, 140 
DegF , wrapped in aluminum foil, baked for 30 minutes, removed from 
oven, a light twist and vo-la ; Off came the can with rubber seal in 
good shape.  Got to love that ATF it softens rubber right up.  Now what?

I still need a DC-9 1000Khz crystal in a sealed can, no screws.

Later
Hutch


Pete Williams wrote:
> Hutch.... the manual says the xtal osc.is set during mnfr for 1000kHz+/- 5Hz
> at 20C. --you've probably heard /seen/done all that. The manual says that
> frequency will not change 'appreciably'if operated within the specified
> limits.... no definition as to what'appreciably' means in the  context.
> The 6 pf is correct... there is also a 1 M resistor paralleling the xtal.
> Have you checked whether it has capacitor tendencies as it warms up ?
> Probably not enough to be a worry.I'd check with a replacement.
> Best of British luck!
> Pete VK3IZ
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of John Hutchins
> Sent: Saturday, February 28, 2009 11:02 AM
> To: milsurplus
> Subject: [Milsurplus] BC-221-AK Looking for DC9 metal can 1000Khz
>
> Callin' Members
> Fixin' BC-221-AK reference crystal oscillator drift down with increased 
> temperature.
>
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