On Wed, 23 Mar 2005 21:48:49 -0800, Mike
wrote:

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.

If the 10V supply has low 120Hz ripple the 9V supply should be even
less. Probably is OK. If in doubt try bridging the PS filter caps with
100-220uF & see if it decreases lots.

Could that cause the freq drift in adjusting the
Fine Attenuator knob?

No - see below...

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.

& from a previous post...

My next problem though is the "Fine attenuator"... when checking the
signal, adjusting this seems to shift the freq...

Quote from pdf - "Operating-Instructions":

"Note - Set the output level before setting the frequency. Although the
oscillator and attenuator are isolated by an emitter follower, slight
frequency pulling can occur when the FINE ATTENUATOR is adjusted or step
attenuators are switched in and out"

An example: On band "D" set the freq to 10MHz.
Turn on the 1MHz xtal calibrator. Adjust freq setting for zero beat.
Slight movement of the Fine Attenuator, in either direction, will
produce a tone. A _very_ small tweak of the freq knob will again zero
beat.

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).

The b-e voltage stays the same at ~0.7V.

The schematic shows 1.3V on the emitter of Q3. You have 2.86V.
Checking my unit I find 2.85V... hmmmm....

Emitter resistor is 330R (on all normal freq bands A-E).
Mine measures 341 ohms (close enough).

I pulled both the DC base bias resistors to Q3, R14 & R16.

R14, 9.1K has drifted to 9.85K
R16, 6.8K has drifted to 7.95K

I replace both with correct values per the schematic (within 1%).

On power up, after a 5 minute warm-up I am back to the _same_ emitter
voltage, 2.85v!

I do not know if Q3 has been replaced at some time.
Q3 is a 2N3440, date code 7615.

I found a 7347 date code on the main, dual section variable-cap & the
meter has 7404.

So either the tuning cap & meter were 2 years old when the transistor
was mfg. or Q3 has been replaced.

After all this it still functions the same. Everything seems to work &
is relatively stable. Good enough for me

Kim