I have checked the power supply and the voltage levels (10v, 9v) are
okay - a scope on the 10v line looks clean to me, the 9v line seems to
have a little ripple. Could that cause the freq drift in adjusting the
Fine Attenuator knob? I checked the rf level and the attenuator is
doing its job of adding attenuation, it just that it also moves the
signal around a little as you change it. The only other thing that
looks fishy to me are some of the voltages associated with the Q3
modulator (which I replaced). The base according to the schematic
should be 2V, I am getting 3.6v. The emitter should be 1.3, I am
getting 2.86. The collector looks okay at 8.6v (schem shows 8.8).

Mike

On Wed, 23 Mar 2005 18:14:58 -0500, "DaveM"
wrote:

The fine attenuator control should not affect the oscillator frequency. If
it does, then you possibly have a power supply regulation/filtering problem.
Or, possibly an attempted modification or repair of the unit that has
changed the circuit.

The power supply components to suspect a
C31, C32 (220uF each)
D6 (10V/1W Zener)
R35 (68 ohms)
R36 (47 ohms)
D4, D5 1N4005

Do you have a manual for the unit? If not, I can email a PDF copy to you
( about 4.5 Mb). It will save you lots of time if you have any
troubleshooting abilities.