Vectronics VEC-830K - Manual (Page 16)

VEC-830K Instruction Manual Single Side-Band Filter Kit
Placement" section Figure 1 for the location of the point labeled GND on the
circuit board.
Neat, turn the receiver volume all the way down, then clip the 9-volt battery to
battery snap. Set SW 1 to the far left position (Hi-Pass). Now turn the receiver
up slightly so you can hear the received signals on the external speaker. The
signal you are listening to is the signal with the high frequencies unaffected,
but all low frequencies below 375 hertz are removed.. Using the tuning knob
on the radio, go find a side-band signal. A good place to find side-band signals
is in the Amateur Radio bands. Once you find a side-band signal, switch SW 1
to the different filter cutoff positions and notice the affect that the filter has on
the received signal. As you progress through the filter cutoffs from 2.5kHz to
1.5kHz you will find the switch position that gives you the best sounding and
cleanest signal.
IN CASE OF DIFFICULTY
No Signal Filtering:
A newly constructed filter that fails to work upon initial power up, generally
requires a very close and careful inspection of all work. Please go back
through all steps of assembly and inspection, referring to the "Parts Placement"
Figures 1, 2, and 3. Most of the time there will be a part that is not installed or
not installed properly, a wrong value part in place of another, or a broken part.
A close inspection at this point will reveal some accidental mistake(s).
Intermittent Filter Operation:
A filter that operates intermittently may have poor solder connections, a
problem with broken wires, or low voltage power source. Self-oscillation, may
be caused by a defective Ul or U2. Also check for dirty or intermittent switch
operation.
Filter Stops Filtering:
A working filter that fails "in-service" generally indicates a failure of one or
both U1 or U2. If you suspect a bad U1 or U2, then do not touch the part with
your fingers.
If the part is bad, it could be HOT and could cause a serious
burn. Other things that should be checked is the supply voltage of
the 9-volt battery and/or broken wires to and from the circuit board and switch.
No Speaker Audio:
No speaker audio can be a symptom of a bad SW I, a broken wire or a bad C9.
Also check the voltage from the 9-volt battery. A broken wire at the audio
input to the filter can also attribute to no speaker audio.
1