Heterodyne Crystal Failures Mode?

[Kenneth G. Gordon]

On 21 Jul 2006 at 13:25, eugene shapiro wrote:

> cases are sealed, only a pro can open and reseal!!!!!

On the crystals? No. I've opened and resealed a number of them. 
Not difficult. They are soldered closed at the bottom. In one case, I 
found a lead to the plated section of a crystal on one side had 
broken loose. Fixed it with conductive paint or glue. Still working.

> 
> Of course check the components in Hi freq osc ckt. These WILL change
> with heat and time before even thinking of opening case, unless you
> are prepared to replace the xtal.

I certainly agree about checking the oscillator circuit components!  I 
have found many severely out-of-spec components in those, and 
other, circuits.

> 
> Hint. Increase frequency stability by: applying a 100 volt zener on
> the basic plug line, usually behind  the LMO then raise the + end of
> plate resister to HI Freq osc and connect it to the New + DC above. 
> This will improve stability from 10 part/meg down to l part/meg. We
> modified the SB line in this manner.

This sounds like an EXCELLENT, and very simple, modification, 
Gene, and I thank you heartily for it! :-)

Ken Gordon W7EKB

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