ALC/Output
Circuit Board
TROUBLESHOOTING CHART
CIRCUIT DESCRIPTION
SYMPTOM
High signal loss, all bands.
High signal loss, one band.
Low output in high power.
A
The function of the low
pass
filter1ALC circuit is to From the filters, the output signal
is
routed through the
attenuate the harmonics present in the driver and power directional coupler. This coupler provides outputs for
amplifier outputs to acceptable levels, and to
provihe ALC forward and reflected power. These outputs are combined to
control voltage in the high power mode.
form an ALC voltage, used in the high power mode. In this
manner, higher ALC voltages are generated when the
POSSIBLE CAUSE
1. Band switch rotor positioned
wrong.
2.
Shorted coaxial cable.
3.
10/15 meter filter components.
Filter components for that
band.
1. PA circuit board.
2.
High line VSWR.
3. Leads of L813 reversed or
L813 defective.
Four low-pass filters are used, one each for 80, 40, 20, and
antenna line VSWR
is
high, reducing the transmitter output
power to a level which will not damage the power amplifier.
15/10 meters. The
15
and 10 meter bands use one filter. as
Ute second harmonic of
15
meters falls well above the 10
meter band. These filters are selected by
a circuit board
-
Q801 and 0802 form
a
switch which changes the ALC time
mounted rotary switch, ganged with the
main
Bad
switch.
constant between Slow (SSB) and Fast (CW and TUNE).
This is the only
bandswitching in the Transceiver which is D803
is
used to provide voltage for the relative power
not solid-state, due to the power levels involved. metering function.
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