[R-390] A Few R390A Issues Zero Adjust

[roy.morgan at nist.gov]

Quoting Grant Youngman <nq5t at tx.rr.com>:...
> I currently have the R-390 on the bench because of a problem with the
> calibrator module (still undiagnosed

Grant,

I remember a comment on the list earlier that the R-390/URR calibrator uses a
1MC crystal, and the mulitvibrator is running if synched correctly at 100 kc. 
So, the adjustment of the multivibrator is somewhat critical.  If the
calibrator is producing about 90 kc or 110 kc, then this is the direction to
look in.

The 1MC crystal will be less expensive to replace (new) than a 200 kc one as
used in the R-390A/URR.  If it's the crystal, you may well find a workable
substitute for very little.  I don't know what might happen if you put a garden
variety crystal into that oven, but of course you could make a plug-in adapter
to use any crystal from an octal tube base.

Roy
K1LKY

Roy Morgan
13033 Downey Mill Road
Lovettsville VA 20180