Vectronics VEC-841K User Manual

Page 20

VEC-841K Owner's Manual

Tunable SSB/CW Audio Filter Kit

1. Set SW1 and SW2 on the VEC-841K to the out position.

2. Set the Frequency and Selectivity controls, R26 and R27, fully clockwise.

3. Turn R27 counter-clockwise about 10% from fully clockwise.

4. Set R24 and R25 on the circuit board to MID-RANGE.

5. Connect the Audio Signal Generator to Signal Input jack, J4. The Signal

input jack (J4) is an RCA phono type and requires an RCA phono plug.

6. Connect an external speaker to J2.

7. Connect the 9-18 volt DC power supply to J3. Power jack J3 requires a

2.1mm coaxial plug with the center pin positive and the outer sleeve
negative.

It is probably best at this point to double check to see that your test equipment is
setup as per the above steps. Also, be sure that the polarity of the power supply
is correct, otherwise damage to the circuit will definitely result when power is
applied.

Test Procedure:

This here is the actual test and alignment procedure. Please follow each step as
it is written and laid out for you. This will ensure that the procedure is done
correctly.

Important Note: If you are going to use a pair of headphones instead of an
external speaker in this test, then be sure to set the SW2 to the ON position,
before you put the headphones on your ears.

1. Turn ON all test equipment and set SW2 on the VEC-841K to ON. You may

hear a pop in the external speaker. You may also hear the audio signal from
the signal generator too. This is normal.

2. Set the Audio Signal Generator 2990 hertz.

3. Set the scope for the best possible display.

4. Connect the oscilloscope to J4 and set the output amplitude of the generator

to 2 volts peak-to-peak.

5. Connect the oscilloscope to the outer lead of R36 (the 68 ohm 1/2 watt

resistor). Connect the oscilloscope ground to the frame of J4.

6. Set SW1 on the VEC-841K to the IN position (NOTCH).

7. Using the frequency controls on the audio generator, set the frequency output

so the signal presented on the scope is at it's absolute MINIMUM amplitude.