Technical description
HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual 4-27
When a button is pressed, it applies a low to one of six input ports of IC1. This
causes the interrupt line to go low, forcing the microprocessor to read the ports.
The microprocessor identifies the row that is low and then polls each column in
turn to identify the actual button that has been pressed. When the microprocessor
has identified which button has been pressed, it performs the function for that
button.
An additional diode D1, is connected to the cathode of D2 and forms part of the
Power On circuit (see page 4-1, Power on).
Select control
The Select knob is a 360°, 16 position, binary encoder. It is continuously
rotatable in either direction. It can be selected to carry out many functions such as
changing the channel, clarifying the received signal, free tuning the transceiver
etc. The microprocessor IC2 detects each step of the control, then increments
either forward or back, in its selected function.
Volume control
The Volume knob is a rotary, digital encoder and its main purpose is to control
the level of audio to the speaker amplifier (see page 4-10, Volume control and
audio output amplifier). It also has other functions in the Setup and Program
modes such as adjusting the LCD back lighting, moving the cursor etc.
Display
The Liquid Crystal Display (LCD) H1 consists of a 122 × 32 character dot matrix
with LED back lighting. It has its own decoder and drive network. The data from
the microprocessor IC2 is sent via the 8–bit data lines to the display.
The back lighting to the LCD is achieved by a bank of LEDs mounted at the back
of the display. The normal intensity of the back lighting is set by the parallel
resistors R16, R17 and R20 with transistors V6 and V13 switched on in series
with the LEDs connected between the "B" rail and ground. When the back lighting
is reduced by the Volume knob on the front panel, the microprocessor IC2
switches off transistors V6 and V13 in sequence to give a total of four levels of
intensity.
The LCD viewing angle is adjustable by the Select knob on the front panel. The
Select knob is controlled by the Pulse Width Modulation Output from the
microprocessor IC2 pin 4 and via a DC filter R13/C13 to IC8/A pin 3. The DC
average of the Pulse Width Modulation appearing across C13 determines the DC
output of IC8/A pin 1. This sets the VEE level to the LCD for the required
viewing angle. It has a control range between –3 and −4 V.
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