Maintenance
HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual 5-7
Removing the PA assembly from the chassis
q Remove the covers (see page 5-5, Removing the covers).
q Disconnect the ribbon connector P1 and the two coaxial connectors J2 and
J3.
q Disconnect all cables between the rear connectors and the Microprocessor
and Audio PCB.
q Turn the unit over (heatsink facing up) and remove the three screws that
secure the PA heatsink screen to the septum panel. Turn the unit over again
(heatsink facing down).
q Remove the three screws and the one stand-off screw located at the four
corners of the PA PCB.
q Carefully slide the PA assembly, complete with the heatsink, to the rear and
clear of the main frame.
Removing the PA PCB
q Remove the four screws that secure the PA transistors to the heatsink.
One of the PA transistor’s retaining screws is concealed by capacitors C107
and C108. Remove these capacitors to gain access to the screw.
q Remove the screws securing the PCB to the heatsink.
The 12 mm long screw removed from the driver heatsink must be returned
to this position when re-assembling.
q Remove the earth screw and the three screws securing the rear panel to the
heatsink.
q Lift the PCB clear of the heatsink. Remove the existing Thermaflow
compound from the components before proceeding with any repairs. Take
care not to damage the mica insulator located under the bias transistor V20.
Re-installing the PA PCB
q Ensure that all the surfaces that touch the heatsink are coated with a thermal
conduction compound before installing the PCB.
q Replace the earth screw and the three screws that hold the rear panel to the
heatsink.
q Replace the screws that hold the PCB to the heatsink.
q Replace the four screws that hold the PA transistors to the heatsink.
q Replace capacitors C107 and C108.
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