On 14 Mar, 07:42, "Anthony Fremont" wrote:
Anthony Fremont wrote:
Doodling with reactance formulas, it appears that 20uH (coincidence?)
would offset 100pF of capacitance fairly well by having a an opposing
reactance (well resistance at this point) of about 450 Ohms at

s/.well resistance at this point.//
It's just inductive reactance, I need more coffee. ;-)

3581kHz, the same as 100pF. I'll try putting the coil I made in
parallel and see what happens. Hopefully it won't short the
oscillator and kill my 15 year old NE602, I only have two spares.

Should I be afraid to do this? Does it need something to block DC current?

Anthony

Your trimmer cap will block any DC flow to ground. If you are really
paranoid then put a 0.1 mfd in series with the crystal.

If you do accidentally ground the crystal input terminal on that
SA602, it only pulls the base of a transistor to ground and thus turns
it off. That shouldn't hurt anything.

While you may not be able to purchase new "602's" now (they are long
ago declared obsolete) the Phillips SA-612 is the same unit and is
readily available from a number of outlets.

A datasheet for this device is located at:

http://www.nxp.com/pip/SA612AD_01.html

Arv - K7HKL
_._