HYT TM-628H User manual

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Contents
Introduction............................................................................................................................................... 2
Safety Information.................................................................................................................................... 3
Radio Overview ........................................................................................................................................ 5
Software Specification............................................................................................................................. 8
Circuit Description................................................................................................................................. 19
Semiconductor Data............................................................................................................................... 24
Component Description......................................................................................................................... 29
Parts List 1 .............................................................................................................................................. 30
Tuning Description................................................................................................................................. 93
Terminal Function................................................................................................................................. 105
Troubleshooting Flow Chart ............................................................................................................... 108
Disassembly and Reassembly for Repair.......................................................................................... 112
Exploded View...................................................................................................................................... 115
Parts List 2 ............................................................................................................................................ 116
Packing.................................................................................................................................................. 117
PCB View............................................................................................................................................... 118
Block Diagram ...................................................................................................................................... 118
Schematic Diagram.............................................................................................................................. 118
Specifications....................................................................................................................................... 118

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Introduction
Manual Scope
This manual is intended for use by experienced technicians familiar with similar types of communication
equipment. It contains all service information required for the equipment and is current as of the
publication date.
Safety Information
The following safety precautions shall always be observed during operation, service and repair of this
equipment.
This equipment shall be serviced by qualified technicians only.
Do not modify the radio for any reason.
Use only HYT supplied or approved antenna.
Gain of antenna must not exceed 3dBi for VHF or 5.5dBi for UHF.
Mobile antenna Installation: Install the mobile antenna at least 82cm (32 inches) away from your
body, in accordance with the requirements of the antenna manufacturer/supplier.
Transmit only when people inside and outside the vehicle are at least the minimum distance away
from a properly installed, externally mounted antenna.
Mobile antenna substitution: Don’t substitute HYT supplied or approved antenna, or excessive radio
frequency radiation will result. Please contact your dealer or the manufacturer for further
instructions.
Please make sure there’s no stress on the antenna joint during transportation or installation.
To avoid electromagnetic interference and/or compatibility conflicts, turn off your radio in any area
where posted notices instruct you to do so. Hospital or health facilities may be using equipment that
is sensitive to external RF energy.
For vehicles with an air bag, do not place a radio in the area over an air bag or in the air bag
deployment area.
Turn off your radio prior to entering any area with explosive and flammable materials.
Do not expose the radio to direct sunlight over a long time, nor place it close to heating source.

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▇
▇▇
▇Operation Guidelines
For vehicles equipped with electronic anti-skid braking systems, electronic ignition systems or electronic
fuel injection systems, interferences may occur during radio transmission. If the foregoing electronic
equipments are installed on your vehicle, please contact your dealer for further assistance to make sure
that radio transmission will not interfere with these equipments.
For radio installation in vehicles fueled by LPgas with LP gas container within interior of the vehicles, the
following precautions are recommended for personal safety.
1. Any space containing radio equipment shall be isolated by a seal from the space in which the LP gas
container and its fittings are located.
2. Remote (outside) fitting connections shall be used.
3. Good ventilation is required for the container space.
▇
▇▇
▇Installation Guidelines
Vehicle installation: The antenna can be mounted at the center of a vehicle metal roof or trunk lid if
the minimum safe distance is observed.
Do not mount the mobile radio overhead or on a sidewall unless you take special precautions.
If the mobile radio is not properly installed, road shock could bump the radio loose, and the falling
radio could, in some circumstances, cause serious injury to the driver or a passenger. In case of
vehicle accidents, even when properly installed, the radio could break loose and become a
dangerous projectile.

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Radio Overview
Front Panel View
①Volume Control Knob
Turn the Volume Control Knob clockwise to increase the volume, or counter-clockwise to decrease the
volume.
②LCD
Please refer to the “LCD Display” section for details.
③Programmable Functions Keys ([▲]/ [▼])
The [▲]/ [▼]keys are programmable with auxiliary functions by your dealer. Please refer to the
“Programmable Functions Keys” section.
④LED Indicator
⑤Speaker
⑥Power Switch
⑦Programmable Functions Keys ([P1]/[P2]/[P3]/[P4])
The [P1]/[P2]/[P3]/[P4] keys are programmable with auxiliary functions by your dealer. Please refer to
the “Programmable Functions Keys” section.

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⑧Mic Jack
Rear Panel View
①15-Pin Connector (for external expansion)
②External Speaker Jack
Used to connect the external speaker (for the 3.5mm plug only).
Note: Please refer to “Test Cable for Speaker Output” in “Tuning Description” for details.
③Power Inlet
Used to connect the HYT -authorized DC power cable for input of 13.6V DC power.
④Antenna Connector
Used to connect the external connector.
Microphone
LED Indicator▇
▇▇
▇
Indicator Description
Solidly glows red The radio is transmitting signals.
Solidly glows green
The radio is receiving signals.
Flashes orange The radio has received encoding squelch, select calls or 2-tone calls.

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Programmable Function Keys▇
▇▇
▇
The P1-PF4 and ▲/▼keys can be programmed with auxiliary functions below:
1. Off
2. CH Up
3. Channel Down
4. Zone Up
5. Zone Down
6. MONIA
7. MONI B
8. MONI C
9. MONI D
10. Display Frequency
11. Display Mode Switch
12. User Selectable Tone
13. Sel 2-Tone
14. TX Power
15. Scan
16. Add/Del
17. Reverse frequency
18. TalkAround
19. Selectable Squelch Level
20. Home Channel
21. Public Address
22. Scrambler
23. Compander
24. Emergency Call
25. HDC Encode
26. Lone Worker
27. Whisper

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28. Short Message
29. Rent Time Inquiry
30. AUX A
31. AUX B
▇LCD Display
Figure 1 LCD panel
Indicator Description
Displays CH number/name, zone number/name, DTMF
number, frequency, menu and options, etc.
Lo
Indicates low power output.
Press the Monitor key:
1. The icon is displayed when CTCSS/CDCSS and
2-Tone decoding is off.
2. The icon is displayed when the speaker is unmuted.
Appears when the radio begins to scan
Appears when the radio is transmitting a selected call.
C indicates that the current channel is in the scan list.
Z indicates multi zone scan.
Appears when the Scrambler feature is enabled.
Appears when the Compandor feature is enabled.
Appears when the current channel is already in use.

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Indicates the current channel is the priority channel. P•
indicates priority channel 1, P . indicates priority channel 2,
P : indicates priority channels 1 and 2.

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Software Specification
Frame of Radio Modes
Keypad Entry for Mode Startup
Mode Display Operation Remarks
User Mode Welcome Screen and then CH
number The radio enters User Mode upon power-on.
Conventional
Mode
Panel Tuning Mode
TXHIGH Power the radio on while
holding down P1.
Model Set Mode DESTINA0 Power the radio on while
holding down P2.
Clone Mode
CLONE
Power the radio on while
holding down P3.
Firmware Version
Display Mode
Firmware Version VX.XX.XX
Power the radio on while
holding down P4.
PC Mode PROGRAM
Connect the mobile radio to
PC via the programming
cable, and then send
commands via PC.
User Mode
Power on the radio and you will enter this conventional mode.
PC Mode
Tuning Mode
Conventional Mode
User Mode
Model Set Mode
Clone Mode
Wired Clone Mode
Wireless Clone Mode

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Panel Tuning Mode
You can perform tuning in the following steps:
1) Power on the radio while holding down P1 to enter the tuning mode.
2) Use ▲/▼to select the tuning item, and press P4 to enter.
3) After you enter the sub-item by pressing P4, use ▲/▼to adjust the parameter, and press P4 to save
and enter the next sub-item; or press P1 to return to the previous menu without saving the settings.
Tuning items and display (***: 1-256): Please go to Tuning Description---Panel Tuning Mode---Tuning
items and Display for details.
Model Set Mode
You can go with operations in this mode as follows:
1) Power on the radio while holding down P2 to enter the Model Set mode. At this time, the LCD displays
“DESTINA.*”, where “*” represents the model number.
2) Use ▲/▼to select the model number 0-5.
3) Press P4 to confirm your selected model number. The LED glows orange and the LCD displays
“WAIT”.After reset, the radio enters User mode.
Note:
1. Once a new model is set by pressing P4, the previously stored channel information (such as
frequency, CTCSS/CDCSS and functions assigned to each channel) will be cleared, and some
functions will also be changed. Therefore, do not perform this operation unless it’s very necessary
(e.g. when EEPROM is replaced).
Clone Mode
Data can be transferred from radio to radio either by wired cloning or wireless cloning. Operation
methods are given in the following paragraphs.
Wired Clone Mode
1) Power on the source radio while holding down P3. The radio displays “CLONE” and enters Clone
mode or enters User Mode if Clone Mode is set OFF by your dealer.
2) Press P3 to switch between Dealer Clone Mode and Factory Clone Mode, with “DEACLONE” and
“FACCLONE” displayed respectively. The radio restores its original display mode in 5 seconds.
Dealer Clone Mode is the default mode in which tuning data and embedded messages will not be

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cloned. However, in Factory Clone Mode, all data will be cloned.
3) Connect two radios using a clone cable, and then turn on the target radio.
4) Press P4 on the source radio to start cloning. LED on the source radio glows red, and it begins to
transmit data to the target radio. During the cloning process, LCD of the target radio displays
“PROGRAM” and its LED glows green. Upon completion of cloning, LCD of the source radio
displays “END”. And the target radio automatically enters User Mode after receiving all data.
5) Press P4 on the source radio to return to Clone Mode, and “CLONE” is displayed. Repeat the above
steps for further wired cloning.
Wireless Clone Mode
1) Power on the source radio while holding down P3. The radio displays “CLONE” and enters Clone
mode or enters User Mode if Clone Mode is set OFF by your dealer.
2) Press P1 to enter Wireless Clone Mode. The LCD displays “WIRELESS” for about two seconds,
and then displays its channel frequency (wireless cloning is performed at this frequency). Press P1
again to return to Clone Mode, or press ▼to switch the channel for wireless cloning.
3) Press P3 to switch between Dealer Clone Mode and Factory Clone Mode, with “DEACLONE” and
“FACCLONE” displayed respectively. The radio restores its original display mode in 5 seconds.
Dealer Clone Mode is the default mode in which tuning data and embedded messages will not be
cloned. However, in Factory Clone Mode, all data will be cloned.
4) For the target radio, repeat the above steps 1) and 2), and set its cloning frequency the same as that
of the source radio. Place the target radio close to the source radio, and press P4 of the source
radio to start cloning.
5) The source radio is transmitting data to the target radio. During data transmission, the source radio
displays the percentage of the transmitted data, with red LED glowing. During data receiving, the
target radio displays the percentage of the received data and a “BUSY” icon, with orange LED
glowing.
6) Upon completing of data transmission, LCD of the source radio displays “END” and the LED flashes
red. Press P1 to read the cloning frequency and repeat the above steps to continue. The target
radio enters User Mode automatically after receiving all data.
Note: Clone Mode can be enabled or disabled by your dealer. You can perform cloning only when such
mode is enabled by your dealer.

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Firmware Version Display Mode
Power on the radio while holding down P4. The LCD displays the firmware version accordingly. Release
P4 to enter User Mode automatically.
PC Mode
Connect the mobile radio to a PC using a programming cable. Data can be transmitted to the mobile
radio and saved in the EEPROM.
You can configure the parameters and tune the mobile radio via the programming software.
1）Once PC starts to transfer data to the mobile radio, “PROGRAMM” will be displayed on the LCD.
When the data is written to the mobile radio, the LED glows green; and when the data is read from
the mobile radio, the LED glows red. The mobile radio will reset automatically when programming is
completed.
2）The following items can be set via programming software:
TX High Power
TX Low Power
Maximum Frequency Deviation
CDCSS Balance
CTCSS Deviation (67.0Hz)
CTCSS Deviation (151.4Hz)
CTCSS Deviation (254.1Hz)
CDCSS Deviation
DTMF Deviation
MSK Deviation
Single Tone Deviation
RX Sensitivity
Squelch ON Level (9)
Squelch ON Level (3)
Squelch OFF Level (9)
Squelch OFF Level (3)

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Key Assignment
Your dealer may assign one of the following functions to the programmable key (P1/ P2/ P3/ P4/ ▲/ ▼).
See the table below for reference.
Key Assignment
No.
Function
Key Settings Display Remarks
1 P1-P4
&
▲/▼
Off No function
CH Up CH Information Channel up
CH Down CH Information Channel down
Zone Up Zone Information Zone up
Zone Down Zone Information Zone down
MONI A MoniA Icon
Monitor A: Monitor Unmute –
Momentary
MONI B MoniB Icon Monitor B: Monitor Unmute – Toggle
MONI C (default) MoniC Icon Monitor C: Carrier Unmute –
Momentary
MONI D MoniD Icon Monitor D: Carrier Unmute – Toggle
Display Frequency CH Frequency Displays the channel frequency
Display Mode Switch Mode Information
Displays the channel number, channel
label, zone number, zone label and
channel frequency.
User Selectable Tone UST Information Tone 01-32 (CTCSS/CDCSS)
Sel 2-Tone 2-Tone Information Selects 2-Tone encode
TX Power
Power Icon
Displays when the TX power is low
Scan SCAN and Icon Scan
Add/Delete CH Information
Adds or deletes scan channel in
non-scan status
Temporarily deletes nuisance channel
Reverse RE and CH Number
Reverse frequency
Talk Around TA and CH Number Talk Around
SEL SQL SQL Level Selects squelch level
Home CH
HOME and CH
Number Home Channel
Public Address PA Public Address
Scrambler Scrambler Icon Scrambler
Compander Compander Icon Compander
Emergency Call Emergency Emergency Call
HDC Encode HDC Menu HDC call
Lone Worker LONE ON/OFF Lone Worker
Whisper WHISP ON/OFF Whisper

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Short Message Message Menu Short Message
Remaining Rental Time
Inquiry Remaining Time
Inquires about the remaining rental time
AUX A AUX A AUX A
AUX B AUX B AUX B
2
HOOK/ MONI
Hook Check
This option should be selected when palm
microphone is used.
Monitor
This opti
on should be selected when desktop
microphone is used.
3
Selector
Knob
Selector Knob
For controlling the volume as well as
selecting the channel and zone
Circuit Description
Frequency Configuration
The receiver utilizes double conversion superheterodyne. The first IF is 49.95MHz and the second IF is
450KHz. The first local oscillator signal is supplied by the PLL circuit, while the second local oscillator
signal (49.5MHz) is generated from the frequenc MHz The PLL circuit generates the frequencies
required for transmission. See Fig.1.
Frequency Range VHF: 136MHz-174MHz
UHF: 400MHz-470MHz;
Receiver Circuit
The receiver section configuration is shown as Fig. 1.
Fig. 1 Receiver Circuit
2.1 RF AMP BPF
The circuit consists of front-stage BPF, RF amplifier (Q111) and final-stage BPF (D110 and D111). The

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bandpass frequency range varies with the radio models. The BPF is used to eliminate unwanted signals
and let only wanted signals go to the mixer.
2.2 First Mixer Circuit
The signal output from RF AMP&BPF is mixed with the first LO signal from the PLL circuit at the mixer
(D112) to generate a 49.95MHz first IF signal. Then the first IF signal will feed through a crystal filter
(IF200) to further remove spurious signals.
2.3 IF Amplifier Circuit
After amplified at Q113, the first IF signal enters IC102 (TA31136FN), where it is mixed with the second
LO signal (50.4MHz) to generate a 450KHz second IF signal. Then the second IF signal feeds through a
pair of ceramic filters (N: CF202; W: CF203) where unwanted signals are removed. Finally the signal
goes to the frequency discriminating circuit of IC102 to output audio signal from Pin 9.
2.4 Audio Amplifier Circuit
The audio signal from IC102 is amplified and filtered at IC402, and then amplified again at IC401 (the
received signaling is separated and sent to CPU for decoding). Then the signal passes through Q406
(AF MUTE), and enters IC405 for further amplification. After the volume is controlled at K301 on the
control panel, and SP MUTE is controlled at Q511, the signal feeds into IC511 to output audio signal to
drive the speaker.
2.5 Squelch Control Circuit
One flow of the audio signals from IC102 feeds into IC102 (from Pin8) for amplification, filtering and
rectification, and then a SQL level is derived. Then the SQL level is sent to CPU (IC502) for comparison
with the reference level to generate a level which controls AFMUTE and SP MUTE. The level controls
Q406 and Q511 to open or close the audio channel.
Transmitter Circuit
The transmitter circuit is composed of MIC circuit, modulation circuit, RF driver, final-stage power
amplifier circuit and APC circuit.

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Fig. 2 Transmitter Circuit
3.1 MIC and Modulation Circuit
The audio signal from MIC is amplified at IC405, and further amplified, pre-emphasized and encoded at
IC 401. It is added with signaling before going to VCO for modulation.
The DI modulation circuit is composed of IC407 and peripheral circuits (see the figure above). The signal
goes to the DI modulation circuit via the TXAF_DI port, and then goes to the VCO unit. The signal
amplitude can be adjusted manually via VR802, allowing accurate modulation of DI without any
distortion. This circuit can serve as input or output port for GPS and encryption, promoting the radio
functions to be further expanded.
3.2 RF Driver and Final-stage PACircuit
TX-RF signal output from Q703 in the VCO circuit is amplified at Q101, driver PA Q110 and Q109, and
final-stage PA IC101. The signal passes through LPF and goes to the antenna for transmission.
3.3 APC Circuit
The circuit is used to keep output power at a constant preset value. In this circuit, D101 and D102
convert the signal from detector into DC voltage, which is then compared with the reference voltage from
CPU in IC104 to output a DC voltage. The DC voltage controls gate electrode of IC101, so as to control
the output power.
4. PLL Circuit
PLL circuit supplies frequency to receive the first LO signal and TX signal. The circuit consists of TX

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frequency oscillator (Q701), RX frequency oscillator (Q702), buffer amplifier (Q703), RF amplifier (Q102),
PLL IC (IC801), LPF and TX/RX VCO switch (Q704/Q706).
In TX mode, IC502 provides the frequency data to and activates PLL IC. Meanwhile, Q704 is turned on
to activate TX VCO. The output signal is amplified by Q703 and Q102. Then PLL IC divides the signal
into 2.5KHz, 5KHz or 6.25KHz. And phase of it is compared with that of reference frequencies 2.5KHz ,
5KHz or 6.25KHz from the 16.8MHz crystal oscillator. The crystal oscillator has operating frequency of
16.8MHz and frequency stability of 2.5ppm. The frequency control voltage output from the phase
comparator passes through LPF (Q802 and Q803), and then is sent to TX VCO. In the meantime, TX
modulation signal is passed to TX VCO for frequency modulation.
The working principle of RX mode is similar to that of TX mode.
Fig. 3 PLL Circuit
5. Control Circuit
The circuit comprises CPU circuit, reset circuit and power control circuit.
5.1 CPU

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IC120 (CPU) operates at 9.8304MHz, and controls EEPROM (IC501), RX circuit, TX circuit, control
circuit and display circuit, as well as data transmission with peripheral equipment.
Fig. 4 Control Circuit
5.2 Reset Circuit
The reset circuit consists of a reset IC (CN813LESA) and peripheral circuits. When a breakdown occurs
due to change of external voltage, the CPU would automatically reboot your radio through the reset IC
(IC901).
5.3 Power Control Circuit
Power supply of the radio is derived from +B. D515 and D516 are diodes for over-voltage protection. The
power can be switched on or off via software (see the figure below):

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Fig. 5 Power Supply Circuit
Vout supplies power for IC601, IC602 and IC803, which generate 8V, 5V and 3.3V voltage respectively
to supply the whole circuit.
6. Display Circuit
Display circuit comprises CPU (IC502), LCD, LED and other components. Application can be operated
manually through programmable keys P1-P4 as well as ▲and ▼. Channel information is displayed on
the 14-segment display.

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Semiconductor Data
1. Positive voltage regulator: TA7805F (Power Unit IC602), TA7808S (Power Unit IC601)
2. EEPROM: CAT24C256WI 256K CATALYST (CPU Unit IC501)
2-1. Pin Function
Pin Function
Pin No. Name I/O Function
1～3 A0～A2 I Address input
4 GND Ground
5 SDA I/O Serial data input/output
6 SCL I Serial clock input
7 Write Protect Write protect
8 VCC +5V