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Table 2 - Switch Input And Output Description
NAME
PIN NO
Input/Output
R1
15
Output
R2
14
Input
R3
10
Input
R4
11
Input
C1
9
Output
C2
1
Output
C3
12
Output
C4
13
Output
Table 3 - 4X4 Cross Point Switching
FUNCTION
MODE
I/O
CTCSS
Receive
R4.C3
Transmit
R1.C2
R3.C3
R2.C2
DCS
Receive
R4.C3
R2.C4
Transmit
R1.C2
R2.C2
R3.C3
WARNING
R3.C1
SELF CHECK
R3.C3
During TX mode the CTCSS/CDS tone encoding circuit
generates the tone squelch digital signal and produces a 3-bit
parallel word at pins 18 (1), 19 (2) and 21 (8) of the microcon-
troller. The 3-bit digital signal is converted to an analog signal
by resistors R421-424. RV403 is used to adjust signal devia-
tion. The analog signal is passed to digital filter IC407-8
through pin 10 and 14 of 4 x 4 cross switch IC406. The filtered
output at IC407-3 is connected to IC406-14 and fed to pin 1
(CTCSS) and pin 15 (DCS). The CTCSS signal at IC406-1 is
passed to the VCO module through R46 and Flexi PCB 1,
connector 16. The DCS signal at IC406-15 is passed to Q409,
RV401 and IC404 A and B. RV401 is used to adjust DCS
DESCRIPTIONS
To Modulation Circuits
From Filter Output
From Tone Generator
From Signal Receive Circuits
To Warning Tone Indication Circuits
To TCXO
To Filter Input
To DCS (or CTCSS Tone Coupling)
distortion. IC404 A and B form a low pass filter. The output is
passed to the VCO module through Flexi PCB 1, connector 15.
Control And Indicator Circuits
External PTT Control Circuit - When the external micro-
phone is connected at the adaptor socket (pin 4) on the top panel
circuit board, the CONT control line on the control printed
circuit board is at logic 0, switching IC401A off to disable the
internal microphone. The CONT control line is also connected
to the junction of R416 and C478 at IC405. IC405D is a voltage
comparator with R416 DC. When PTT is pressed, IC405D-13
goes below 2V and output 14 goes high (+5V), turning on
Q402. The PTT control line is pulled low, enabling the radio
transmitter through D401.
Channel Select Circuit - One of 10 channels may be
selected using the channel switch (CH) on the top panel. The
channel switch encodes the channel number selected into a
4-bit binary word. Periodically the microcontroller enables
IC411-1. The 4-bit binary word from the RF printed circuit
board is passed through the 4-bit inverting buffer to the micro-
controller data I/O lines 1, 2, L1, and 8 through the control
printed circuit board, the flexible PCB2 and then to IC411.
IC411 inverts the binary word. The inverted binary word is then
decoded by the microcontroller, enabling the appropriate RX
or TX frequency and associated data to be selected from the
EEPROM.
Data present at the I/O lines is compared with previously
sampled data. If a difference in data is detected, the microcon-
troller enables EEPROM IC408 and selects the RX or TX
frequency datacontrolling the frequency synthesizer circuit for
the channel selected.
Battery Low Indicator Circuit - Should the battery
voltage drop below 8.86 Vdc, IC405B (voltage comparator)
turns on Q403. The microcontroller then enables the red
LED indicator and at the same time disables the transmitter.
The battery must be replaced or recharged before continuing
operation.
I/O Control Circuit - IC403 and IC411 are input/output
buffers to isolate noise and are enabled by the microcontrol-
ler. IC411 is a tri-state 2-bit and 4-bit inverting buffer. The
4-bit output is enabled when pin 1 is at logic 0 (0 V). The
2-bit output is enabled when pin 15 is at logic 0 (0 V). IC403
is a non-inverting TTL to CMOS level shifter and output
buffer supplying data to the RX/TX printed circuit board.
EEPROM
Rx/Tx channels, CTCSS, DCS as well as other data from
the programmer are stored in the EEPROM. The data stored
is retained during power outages and when the power is off.
This is a non-volatile memory. The EEPROM may have
information re-programmed or erased. IC408 is an EEPROM
with 1024 bit (8 x 128) capacity. Data are written and read
serially.
SERVICE SECTION
The Service Section contains information designed to
assist you in rapidly identifying any problem areas and in
tuning and adjusting the radio for optimum performance. A
diagnostic section is included to help you, through the use
of indicators and tones, to learn the current operating status
of the radio.
CARE OF EQUIPMENT
1.
Keep the exterior of the radio clean. Use a soft damp
cloth.
2.
To ensure efficient power transfer from battery to
radio, wipe the contacts of the battery and radio to
remove dirt or grease. Use a soft dry cloth.
3.
When the accessories connector is not in use, cover
the connector with the protective dust cap to prevent
the build up of dust or water particles.
LBI-38861C
CAUTION
Do not carry or hold the radio by the antenna.
Do not use chemical cleaners, aerosol sprays or
petroleum based products when cleaning the radio. They
may damage the radio housing.
DIAGNOSTIC ANALYSIS
An analysis of the status indicators and audible tones are
provided in Table 4.
ELECTROSTATIC DEVICES
CMOS Integrated Circuit devices used in
this equipment can be destroyed by static
discharges. Before handling one of these
devices, the service person should discharge
himself by touching the case of a bench test
instrument that is equipped with a 3-prong
power cord connected to an outlet with a known good earth
ground. When soldering or desoldering a CMOS device, the
soldering iron being used should also have a 3-prong power
cord connected to an outlet with a known good earth ground.
A battery operated soldering iron may be used in place of a
standard soldering iron.
REMOVAL AND REPLACEMENT
NOTE
When disassembling or reassembling the radio, refer
to the Parts Breakdown drawings and Parts List for
assistance.
7
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