Maintenance
5-12 HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual
Table 5 -4: PA & Filter PCB supply voltages
[1 04-02973 and 04-03096]
Supply Description Regulator
"A" rail
+13.6 V nominal unregulated supply
+5 V
+5 V ±0.2 V regulated supply
(selected in transmit only)
IC2
+5 V
+5 V ±0.25 V zener diode supply
V1
No reception
q Check the Mute gate is closed (IC206 pin 12, +10 V) [1 04-02976].
q Check the supply voltages are correct (see page 5-11, Voltage
measurements).
q Check the AGC measures 5.5 V ±0.3 V on the Rx/Exciter PCB [1
04-02972 Sheet 2]. If the AGC = 0 V, then check if IC209 pin 6 = 5 V when
in Transmit mode.
q Use a signal generator and a series capacitor (about 100 nF) to apply a signal
to the test points shown on the circuit diagrams. The receive levels and
frequencies, shown on the RF and IF circuit diagrams, should cause the
AGC to fall by about 0.5 V from its no signal level of approximately 5.5 V
(under no fault conditions).
Start at the 455 kHz IF amplifier and proceed back through the receive path
towards the antenna. When the injected signal can not be heard any more or
the AGC stops falling by 0.5 V (when applying levels shown on the circuit
diagram), a close examination between the satisfactory and failed check
points should indicate where the fault lies.
q In the case of an audio fault, apply a signal from the Signal Generator to the
receiver input at a frequency set to approximately 1 kHz above the channel
frequency (1 kHz below for LSB). With the aid of an oscilloscope, trace the
audio signal path from the demodulator output to the loudspeaker.
If the AGC is operating satisfactorily, the audio signal should be present at
the output of pre-amplifier IC204/A test point TP206 (Rx DEMOD) [1
04-02972 and 04-03135]. This point provides the audio to the AGC circuit.
q If the receive fault shows as an oscillation or instability, check that the
transmit mixers IC5 and IC8 do not have DC on pins 4 or 11 (< 0.5 V) [1
04-02972 and 04-03135]. Check the modulator IC202 has no DC applied to
pin 5.
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