Kirisun FP420 User manual

FP420 Service Manual
Page 1 of 50
Contents
Chapter 1 Overview ...........................................................................................................2
Chapter 2 External View and Functional Keys...............................................................3
Chapter3 Circuit Description............................................................................................6
Chapter 4 Function Description and Parameter Settings ...........................................16
Chapter5 Disassembly for Repair..................................................................................18
Chapter 6 Adjustment......................................................................................................26
Chapter7 Major Specification.........................................................................................27
Chapter 8 Service and Test Equipment.........................................................................28
Chapter 9 Troubleshooting.............................................................................................29
Appendix1 Abbreviation..................................................................................................31
Appendix 2 Electronic Parts List ...................................................................................31
Appendix 3 Spare Parts List (Structure Part) ...............................................................39
Appendix 4 Accessories reference List ........................................................................41
Figure1 FP420 Schematic Pane Diagram......................................................................42
Figure2 FP420 Top Board Position Mark Diagram.......................................................48
Figure3 FP420 Bottom Board Position Mark Diagram.................................................49

FP420 Service Manual
Page 2 of 50
Chapter 1 Overview
1.1 Introduction
This manual applies to the service and maintenance of FP420 FM portable radios, and
is intended for use by engineers and professional technicians that have been trained by
Kirisun. It contains all the required service information for the equipment. Kirisun reserves
the right to modify the product structure and specifications without notice in order to
enhance product performance and quality. You can also contact your local dealer or us to
get the latest service manual.
Please read this manual before repairing the product.
1.2 Safety Precautions
* Electromagnetic Energy Exposure
Radios will generate and radiate electromagnetic energy during transmit mode.
Kirisun radio is designed to comply with a number of national and international
standards for human exposure to radio frequency electromagnetic energy.
In order to obtain best performance, and to guarantee that the electromagnetic
radiation does no harm to you, always keep the radio in a vertical position to the ground
and make sure that the microphone is 2-5cm from your mouth while using.
* Electromagnetic Interference
In order to avoid electromagnetic interference, please turn off the radio in the place
where such post prompts you to do so, e.g. hospital, health care center, airport and etc.
* Explosive Atmosphere
It’s prohibited to use the radio in the following places:
Any area with a potentially explosive atmosphere, e.g. orlop deck of the ship, storage
and transportation equipment for fuel and chemical, where the air with chemical
substance, particle or iron dust.
Any place near blasting sites or area with electrical blasting cap.
It is also prohibited to change or charge the battery in any area with a potentially
explosive atmosphere.
* Antenna
If the antenna has been damaged, do not use the radio. Damaged antenna may cause
light burning to skin.

FP420 Service Manual
Page 3 of 50
* Replacement Parts
All components used for repair should be supplied by Kirisun.
Components of the same type available on the market are not surely able to be
used in this product and we do not guarantee the quality of the product using such
components.
1.3 Service
All the Kirisun products are subject to the service warranty.
The warranty of the host is 18 months. The warranty of the accessories, including
battery, charger, earphone, antenna and adapter, is 6 months. However, in one of the
following cases, charge free service will not be available.
* No valid warranty card or original invoice.
* Malfunction caused by disassembling, repairing or reconstructing the radio by users
without permission.
* Wear and tear or any man-made damage such as mechanical damage, burning or
water leaking.
* Product’s serial number has been damaged or the product trademark is difficult to
identify.
After the warranty expires, lifetime service is still available. We also provide service
components to service stations and staffs.
Chapter 2 External View and Functional Keys
2.1 External View and Functional Keys

FP420 Service Manual
Page 4 of 50
Figure 2.1
○
1Antenna
○
2PTT
Press the key and talk to make a call; release the key to listen
○
3PF Button
The button can be assigned different functions through PC software by your dealer.
Details refer to the following “Programmable Key” in this instruction.
○
4Speaker
Output the voice
○
5Channel Knob
Rotate to choose 1—16 channels.
○
6On/Off Key and Volume Knob
Clockwise rotate the knob to turn on the radio, and counterwise rotate the knob until
there is a click sound to turn off the radio.
Rotate the knob to adjust the volume when the radio is on.
○
7LED Indicator
When transmitting signal it indicates red, when receiving signal it indicates green. It
flashes when the power is not enough.
○
8Microphone
Input the voice
○
9External Connector
Open the cover to connect external speaker and microphone.
○
10 Belt Clip
○
11 Pushing Buckle
2.2 Functional Keys Operation Instruction
Programmable Keys
Below keys can be set through PC software by dealers:
Long press key and short press key can be set: PFkey
Long press key can be set：Menue Key/ Cancel Key
NOTE：
Short press：Press down and release instantly.
Long press：Press down and keep 2 seconds to release.
Available functions to be chosen:
None：No feature will be assigned.
Power level adjustment: Switch between high/low power

FP420 Service Manual
Page 5 of 50
Moniter: If the current analog channel is with CTCSS/CDCSS, press the key to squelch
mode to cancel the CTCSS/CDCSS function. Press the key again to return to the original
status.
Emergency alarm open: Start the EmergencyAlarm function to seek help.
Emergency alarm close: Finish the EmergencyAlarm function.
Squelch open/close: Open/close the squelch function to receive weak signal on analog
channels.
Scan: Check activity of other channels. Press the key to open/close this function.
Whisper: When the whisper function is on, others can hear clearly even speakomg in a
low voice.
Aler tone on/off: Open/close the alert tone.
2.3LED Indicator
Red LED lights on: the radio is transmitting.
Green LED lights on: the radio is receiving.
Red LED flashes: low battery, the battery needs to be charged.
2.4 Basic Operation
Turn On/Off the radio
Clockwise rotate the knob to turn on the radio, and counterwise rotate the knob until
there is a click sound to turn off the radio.
Selecting a channel
Each channel in your radio can be programmed to analog channel or digital channel.
Under the Home Screen, turn the Channel Knob to select a channel.
Adust the volume
Rotate the knob to adjust the volume when the radio is on.
Make a call
On a digital channel, choose one of the following procedures to make a call:
a. Enter Contacts menu, select one contact and then press and hold the PTT Button,
speak to the MIC.
b. Enter Call Log menu, and then enter Call Out or Call In item, select one contact,
press the PTT Button and speak to the MIC.
c. Under the Home Screen, press the PTT Button and speak to the MIC. The call out
number is the default contact number of this channel, which can be programmed by the
dealer, or set through menu.
d. Under the Home Screen, input the number manually, then press the PTT Button and

FP420 Service Manual
Page 6 of 50
speak to the MIC.
On an analog channel, press the PTT Button and speak to the MIC.
Receiving a call
When receiving the signal, the signal strength will be indicated on LCD. While on
digital channels, when receiving private call/group call/all call, the radio will output the
voice. While on the analog channels, when receiving analog signal and the
CTCSS/CDCSS matches, the radio will output the voice.
Anserwing a call
While using digital channels, press PTT within call holding time after receiving the call
to answer the call. If you didn’t answer back during call holding time, you should start a
new call to call back. The call holding time can be set through PC software by dealers.
While using analog channels, press PTT to answer the call directly.
Chapter3 Circuit Description
3.1 Preface
This radio is FM portable radio equipment.
3.2 Frequency Configuration
The reference frequency of RD1846S is generated by 12.8MHz crystal oscillator X500
TCXO.
3.3 Principle of Receiver (RX)
LPF
RDA1846
S
ANT
SW
LT1801A
AF AMP
MIC
12.8MHZ
Q501
Q500
Q503
LNA
32.768KHz
FLASH
18.432MHz
APC

FP420 Service Manual
Page 7 of 50
Figure 3.3 Principle of Receiver
Receiver is mainly used in receiving, selecting, amplifying, transforming, demodulating
etc. and other processing like audio signal amplifying, filtering. Audio part mainly is used
to post emphasis, amplify and filter audio signal.
Receiver Front End
Low noise amplifier is located in the receiver front-end, mainly used in amplifying small
radio frequency signal, in order to provide certain intensity and SNR of RF signal for
subsequent signal processing.
Signals from the antenna transmission (RX/TX) switch (D502 D501, D503, D504), are
sent to Q507 3SK318 and peripheral components consisting of low noise amplifier (LNA)
for enlarging. The enlarged signal will be sent into IC4 (RDA1846S) to demodulate into
output audio signal. 3sk318 noise coefficient is 1.4 db, G about 18 db.
There is input and output match for LNA. Input match adopts best noise figure while
output use maximum power to match, i.e., the amplifier output impedance adjusted to the
load impedance (typically 50 ohm); Input and output impedance of the low noise pipe is
usually high impedance, so the matching circuit using inverted L
Receiver audio signal processing
Audio signal from IC4 (RDA1846S) processed through LT1801, then through the
volume potentiometer, to the audio power amplifier U600 (TDA2822).
LPF
ANT
SW
RDA1846
LT1801A
POWER
SW
AFAMP
LNA

FP420 Service Manual
Page 8 of 50
Audio power amplifier
U600 and peripheral components makes up the audio power amplifier circuit
Q601 base is the control end. High level: U2 begins to make audio; Low level: closed.
Receive audio signals, voice signals, alarm sound signals are summarized and sent to
speaker through audio power amplifier. Among them, the alarm sound will not be limited
by volume control. The speaker impedance: 16 ohms.
3.4 Principle of Transmitter (TX)
Power amplifier and antenna switch principle diagram
Modulated signal from IC4 (RDA1846S), enlarged via Q502, Q503, Q501, are sent to
Q500 power amplifier, and then transmitted through receiving toggle sending into the low
pass filter. LPF will improve as much as possible to harmonic stray signal attenuation in
certain condition of fluctuations in performance. Q500 output power: 4W
Q502 2sc5108 pre-amplifier, mainly to preliminary enlarge output RF signal of
RDA1846S, to provide a certain intensity of the amplifier after excitation signal.
Q503 2sc3356 pre-push RF amplifier is mainly used to provide a certain level of
intensity of excitation signal for subsequent amplifier, so as to guarantee the driving
amplifier can output enough power, to push the last stage power amplifier.
Q501 RD01 promote RF amplifier, is mainly used to promote the last stage power
amplifier, to ensure the output power of the last stage power amplifier to achieve the rated
output power of the transmitter. The output is about 0.5 W, G about 14 db.
Q500 RD07, end RF power amplifier, is part of the important and critical level. The
output power and efficiency level at the end power amplifier are almost equal to
transmitter output power and efficiency. The stability of the last stage amplifier basically
LPF
RDA1846S
ANT
SW
12.8MHZ
Q501
Q500
Q503
Q502
APC

FP420 Service Manual
Page 9 of 50
represents the stability of the transmitter also. Output is 0.8W, G about 12db.
Q500 Q501 grid bias is controlled by APC circuit. Change the gate bias voltage, can
easily control the size of the transmitter output power.
APC (automatic power control) circuit
This circuit changes the gate bias voltage by testing the change of the input to the
power amplifier drain current and changes the output power by changing the gain.
R520 R521, R522 are power amplifier current detection, U502Ais the current sampling
amplifier power amplifier. U502B is the comparison power amplifier.
If the transmitter output power is too large, the power amplifier current increase,
U502A output rise, U502B output voltage drops, applied to Q500, Q501 bias voltage to
drop, lower the transmitter output power, vice versa. In this way, the transmitter output
power is stable under different working conditions.
MCU achieves the goal of setting power by changing the input to the voltage on the
U502B.
Transmitter speech signal processing
MIC signal is sent through the inside and outside MIC switch circuit into No. 11 feet of
IC4 (RDA1846S) to modulate the carrier.
3.5 Principle of power
The machine uses 7.4 V batteries. Transmitter power amplifier circuit (Q500, Q501)
and receiver audio processing (U600) directly uses the battery. All the other circuits are
powered by constant 5 V power supply.
IC100: 5T switch, controlled by MCU.
IC100
5T
5R
IC102
3.3V
IC102
1.8V
1.8V:MCU;BASEBAND;LCD
3.3V:MCU;BASEBAND;LCD
5T:AF; BASEBAND, RF
5R:RF

FP420 Service Manual
Page 10 of 50
5T: supply power for front-end transmitter
5 R: supply power for receiver RF amplifier, audio signal processing unit
etc.
IC102:3C switch controlled by MCU, Provide 3.3 V
3C: receive 3V electricity controlled by power save, supply power for
RDA1846S.
IC102: Provide VCC1.8V
3.6 IC characteristics
RDA1846S features:
3.6.1. Fully integrated CMOS RF front-end
3.6.2, High linearity and low noise amplifier and mixer
3.6.3. Low intermediate frequency receiving channel
Automatic DC offset calibration circuit
High performance analog/digital converter and digital/analog converter
Fully integrated receive filters
The digital AGC
The frequency modulation demodulation technology based on digital signal processing
technology
3.6.4 Direct frequency synthesis pathway
Direct frequency synthesis frequency modulation
Emission filter based on digital signal processing technology
FM digital gain adjustable
Digital voice activation emission control
3.6.5. High-performance decimal PLL frequency synthesizers
Complete piece RF VCO
The complete piece inside the loop filter
Low phase noise
Extremely fast phase lock time
High frequency resolution, frequency is adjustable
The built-in crystal frequency error calibration circuit

FP420 Service Manual
Page 11 of 50
3.6.6. Ultra low power sleep mode
3.6.7. Three line serial digital interface control
3.7 semiconductor devices
MCU instructions
Table 3.7 the microprocessor (LT1801A) port
Pin
NO
I/O
Port
Name
function
E11
IO
SIRIN
SECRET_IO(Reserved for Encryption
chip)
D11
IO
SIROUT
POW_C（Soft switch on power control）
M4
IO
RXD1
RXD(Download program)
J4
IO
TXD1
TXD(Download program)
L4
IO
RXD2
EFUNC1(function key)
K4
IO
TXD2
EFUNC2(function key, monitor key)
A16
IO
SCLK0
GPS Enable Pin
A15
IO
SSN0
TX_LED(Transmitter indication)
B11
IO
SRX0
RX_LED(Receiver indication)
A11
IO
STX0
LAMP(keypad light)
N4
IO
SIMCK
PTT KEY(PTT)
R4
IO
SIMIO
EXT_PTT（PTT for earpiece）
P4
IO
SIMRST
Soft boot detection ( use this if you have
any other functions. Otherwise, please use
POW_ON
A8
IO
RFSO
RFIF Three line SPI serial data output
module
E9
IO
RFSN0
RFIF Modules chosen line of three SPI
piece inside signal is 0
C12
IO
AON
HEADSET_DET(headset detect)
B15
IOU
KB0
KB The keyboard scan input/output
signals [0-7], includes alarm and two
function keys. It is highly recommended to
refer to the design the of hardware
keyboard circuit to make it easier for
compatibility
B14
IOU
KB1
B13
IOU
KB2
B12
IOU
KB3
C16
IOU
KB4
C15
IOU
KB5
C14
IOU
KB6
C13
IOU
KB7

FP420 Service Manual
Page 12 of 50
T3
IO
LCDCRD
LCD_RD
R3
IO
LCDCRS
LCD_RS
P3
IO
LCDCWR
LCD_WR
M3
IO
LCDCS0
LCD_CS
N3
IO
LCDCS1
LCD_RST
K1
IO
LCDC0
LCD_D0
L1
IO
LCDC1
LCD_D1
M1
IO
LCDC2
LCD_D2
A14
IO
SCLK1
SPEAKER_POP/AGC_PD（AGC enable
chip）
B16
IO
SSN1
APC
A13
IO
SRX1
A12
IO
STX1
RX_SW
A9
IO
PWM0
MOTO_EN 或LAMP(Keypad light)
E10
IO
PWM1
LCD_BACK
E7
-
GPO0
P_UL（Indicate frequency lock state）
D7
GPO1
5T（TX power control）
C7
GPO2
5R（RX power control）
B7
GPO3
5C（Radio frequency (RF) public power
control）
CPU please don't use these 4 pins
D9
IO
RFSN1
P_PS（PLL lock indicator）
C9
IO
RFSN2
TX-SW
B5
IO
OSCEN
SPEAKER_EN
B8
IO
RFSCLK
RFIF (Three line SPI clock module )
P6
IO
NC
N1
IO
LCDC3
LCD_D3
P1
IO
LCDC4
LCD_D4
R1
IO
LCDC5
LCD_D5
T1
IO
LCDC6
LCD_D6
K2
IO
LCDC7
LCD_D7
L2
IO
LCDC8
LCD_D8
M2
IO
LCDC9
LCD_D9
N2
IO
LCDC10
LCD_D10
P2
IO
LCDC11
LCD_D11
R2
IO
LCDC12
LCD_D12
T2
IO
LCDC13
LCD_D13
K3
IO
LCDC14
LCD_D14
L3
IO
LCDC15
LCD_D15
G3
AI
Simulation of the
ADC module voltage
input range is 0 to 3 v
VO or VOX
F3
AI
battery voltage detection
E3
AI
RSSI

FP420 Service Manual
Page 13 of 50
D3
AI
BUSY
F5
AO
RFIF
（AUXDA
）
Simulation of DAC
module input voltage
range of 1.15-2.15 V
VCCN(TCXO reference voltage)
E5
AO
RFIF
（AUXDA
）
Simulation of DAC
module voltage input
range is 0 to 3 v
TV/PC
D1
AI
RX_I+
Simulation of the
ADC module for
single-ended input
voltage range 1 VPP,
difference of 2, pp
AFDET
C1
AI
RX_I-
B1
AI
RX_Q+
Simulation of the
ADC module for
single-ended input
voltage range 1 VPP,
difference of 2, pp
A1
AI
RX_Q-
A2
IO
TX_I+
Simulation of DAC
module voltage
output range of
single-ended 1 VPP,
difference 2 VPP
MOD1
B2
IO
TX_I-
A4
IO
TX_Q+
Simulation of DAC
module voltage
output range of
single-ended 1 VPP,
difference 2 VPP
MOD2
B4
IO
TX_Q-
G2
IO
CODEC 16 Ohm 耳
机headphones
negative output
CODEC 16 Ohm Headphones differential
negative output
H2
IO
CODEC 16 Ohm
headphones positive
output
CODEC 16 Ohm Headphones difference
negative output
H5
IO
CODEC The
microphone bias
voltage
MIXBIAS
J2
IO
SPEAKER Linear
output
SPEAKER Linear output
E2
AI
MIC input
input
amplitude=96mv
when 24dB open;
input
MIC2(headphone MIC input)

FP420 Service Manual
Page 14 of 50
amplitude=1.53V
after closed
F2
AI
MIC input
input
amplitude=96mv
when 24dB open;
input
amplitude=1.53V
after closed
MIC1(headphone MIC input)
L5
D10
RXD0 (for GPS)
C10
TXD0 (for GPS)
B10
RTS0 (for GPS)
A10
CTSO (for GPS)
R5
K5
GPIO0_12 Hard boot detection
L7
L8
L9
L10
-
RDA1846S port
AVDD
1
Power supply
SCLK
2
Clock input for serial control bus
SDIO
3
Data input/output for serial control bus
AVDD
4
Power supply
XTAL1
5
Oscillator pin 1
XTAL2
6
Oscillator pin 2,control interface select
MODE
7
When MODE = VL, I2C Interface is select;When MODE =
VH, SPI Interface is select
SENB
8
Latch enable (active low) input for serial control bus
AFOUT
9
Audio signal output to speaker
NC*
10
No connection
MIC_IN
11
MIC input
Cc
12
Compensation capacitor connection
AVDD
13
Power supply
NC*
14
No connection
RFIN
15
RF signal input
AVDD
16
Power supply
NC*
17
No connection
RFOUT
18
RF signal output

FP420 Service Manual
Page 15 of 50
NC*
19
No connection
NC*
20
No connection
AVDD
21
Power supply
PABIAS
22
PA bias supply for PA
AVDD
23
Power supply
PDN
24
Chip enable, high active; Chip sleep, low active
GPIO7
25
Gpio7/vox(When Gpio7=VH, vox is active; else VL)
GPIO6
26
Gpio6 / sq
(When Gpio6=VH, sq is active; else VL)
GPIO5
27
Gpio5 / txon
(When Gpio5=VH, txon is active; else VL)
GPIO4
28
Gpio4 / rxon
(When Gpio4=VH, rxon is active; else VL)
GPIO3
29
Gpio3 / sdo
(Gpio3=VHor VL, it is the output register data in 4 wire
control
Interface mode)
GPIO2
30
Gpio2 / int
(When Gpio2=VH, int is active; else VL)
GPIO1
31
Gpio1 / code_in / code_out
(Gpio1=VHor VL, it is the input/output code data)
GPIO0
32
Gpio0 / css_in / css_out
(Gpio0=VHor VL, it is the input/output CTCSS/CDCSS
signal)
3.8 semiconductor devices functional description
Item
Model No.
Functions
U500
NJM2904
APC，
U400
LT1801A
MCU
IC200
24LC512
E2PROM ，Storage channel frequency data, set
parameters, debugging status parameters
U201
TDA2822
Receiver audio power amplifier
Q500
RD07S2B
end of TX power amplifier
Q504
DTA144EE
APC output switch
Q507
3SK318
Receiver high power
Q200
DTC144EE
Red LED drive
Q201
DTC144EE
Green LED drive
Q501
RD01MUS1
Transmitter power amplifier
Q202
DTC144EE
Audio power amplifier control switch
U404
XC6204B502MR
The adjustable 5 R, 5 T voltage output
IC102
LN2407
1.8V output voltage adjustment
IC103
LN2407
3.3V output voltage adjustment
Q600
FMMT717
Audio output control switch

FP420 Service Manual
Page 16 of 50
Q205
DTC144EE
MIC Switch
Q501
2SC5108
TX 1st amplifier
Q503
2SC3356
TX 2st amplifier
Chapter 4 Function Description and Parameter
Settings
4.1TOT
This function forbids you from occupying the channel for a long time. If the continuous
transmitting time exceeds the setting time by dealer, the radio sends out a warning tone
and stops transmitting. Release the PTT key to stop the warning tone. After a period of
time, which is set by dealer, you can transmit again. And if the radio is programmed with
pre-alert function by the dealer, the radio will send out an alert before the time out timer
expires
4.2 Scan
During scan, the radio checks and stops on a busy channel. Then the radio continues
scanning until the channel is not busy for a while (this time is set by dealer, which is
named as Scan Hold Time).
Steps to start scanning: press the Scan shortcut key select “Start” item. The radio
scans the channels in the current scanning list one by one. During scan, press the Cancel
key or scan shortcut key to stop.
◆Scan revert channel
During scan, press the PTT key to make the radio transmit on a default channel. The
channel can be programmed by your dealer.
4.3Kill、Revive
This function allows one radio to receive the kill and revive signaling from another radio.
The radio to be killed cannot make or receive calls. The radio can only revive through CPS
sends a revive order. After revived, the radio can work normally again. This function is
used to manage the unauthorized usage of the radio, prevent misappropriating the radio
which is lost
4.4Emergency
If you are in danger and this function is enabled, you can press Emergency Alarm On
shortcut key to send an emergency alarm.

FP420 Service Manual
Page 17 of 50
The means of sending emergency alarm are decided by the following parameters:
Alarm Type, which defines the audio and visual reaction when the radio sends an alarm;
Alarm Mode, which defines the content sent to the other members when the radio sends
an alarm. The above parameters can be programmed by dealer.
To turn off the Emergency Alarm, press the programmed Emergency Alarm Off
shortcut key.
Alarm Type:
◆None: No alarm function (Default setting); you cannot send an emergency alarm.
◆Siren Only: The radio only emits siren locally.
◆Regular: The radio provides audio and visual indication that it is in Emergency
mode and can receive the signal from others;
◆Secret: No audio and visual indication. And the radio cannot receive the signal from
others;
◆Secret with voice to follow: No audio and visual indication. But the radio can receive
the signal from others.
Alarm Mode:
◆Emergency Alarm: The radio sends out an emergency alarm, and then exits the
emergency alarm status automatically.
◆Emergency Alarm w/ Call: An emergency alarm is sent, after which an emergency
call can be transmitted by pressing the PTT Button.
◆EmergencyAlarm w/ Voice to Follow: The radio sends out an emergency alarm, and
then sends out background tone periodically and automatically through emergency call.
Note:
EmergencyAlarm: The radio sends out a signal to alert other member.
Emergency Call: A priority call on channel, so as to make sure the successful
communication under emergency condition.
4.5 Parameter Setting(PC Mode)
The radio parameter have been programmed in the factory.The user can reset the
radio parameters such as working frequency, channels, digital functions, QT/DQT, and
auto scaning.We designed a user-friendly and convenient programming software CPSc to
set parameters on the radio. The programming steps are as following:
Install the programming software of FP420
B．Connect the radio to the computer serial port with the specified programming
cable,see figure4.5

FP420 Service Manual
Page 18 of 50
Figure4.5
C．Turn on the radio power
D．Click the CPSc to run the programming software.
E．Click read to read the data from radio.
G．About more details, please refer to help file or programming instrunction manual.
Chapter5 Disassembly for Repair
The radio is a piece of precision communication equipment. Please be careful when
disassembling the radio during service. The instructions for the disassembly are as
follows.
5.1 Disassemble the Battery
Removing the Battery
Make sure the radio has been turned off,
When you remove the battery, ①push the battery latch upwards ②battery will
upspring③remove it away from the radio. ④If the radio with belt, pls pull up the battery.
Installing the Battery
If the radio with belt, ①pls upspring the belt. ②Install the two bulges at the bottom of
the battery pack with the corresponding slots at the rear bottom of the radio. ③Push the
top part of the battery towards the radio to lock it until a click is heard.
Computer(RS232 or USB)
Specifiled programming
cable
Radio(Speaker/MIC
socket)

FP420 Service Manual
Page 19 of 50
Notice:
Do not short-circuit the battery terminals or dispose of batteries in fire.
Do not attempt to disassemble the case of the battery.
5.2 Installing/Removing the Antenna
Installing: Hold the base of the antenna and turn the antenna clockwise into the
connector on the top of the radio until it’s tightened.
Removing: Hold the base of the antenna and turn the antenna anti-clockwise and
remove it.
5.3 Installing/Removing the Belt Clip
Match the grooves of the belt clip to the rear top of the battery, fixed it with two 2.5x6.5
screws. Loosen the two screws fixing clip, you can remove the clip.