TC508 Technical Training
Hytera Communications Co., Ltd
Edited by Adam Sun
01MAR2012
Global Customer Service Center
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Hytera Communications Corporation Limited
Content
1. Function & Feature
2. Technical Specification
3. Software & Setting
4. Disassembly & Re-assembly
5. Circuit Description & Analysis
6. Trouble Shooting
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1. Function & Feature
Features
The TC-508, one of the market-leading products in Hytera's
commercial radio series, is an ideal choice for facilities,
hospitality, manufacturing, retail, education and construction.
As the affordable and reliable two-way radio for business and
industry, TC-508 can largely enhance your productivity and
management efficiency. The excellent design of HYT’s compact
TC-508 portables guarantees superior ergonomics.
Moreover, it can ensure a great performance in any operating
conditions, thanks to MIL-STD 810 & Hytera's 5-year ALT test.
Besides, TC-508 provides up to 14 hours of battery life to ensure
long-lasting performance and convenience. Affordable price and
distinct performance - TC-508 deserves your trust.
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1. Function & Feature
Radio Overview
④Antenna
⑤Channel Selector Knob
①PTT
⑥Radio On-Off/Volume
②SK1
Control Knob
③SK2
⑦Speaker
⑧Microphone
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1. Function & Feature
Main Functions
High/Low Power Switch
Monitor
CTCSS/CDCSS and Tail eliminate
Channel Scan
Battery Save
Low Battery Alert / Battery Strength Indicator
Voice Operated Transmit (VOX)
Busy Channel Lockout (BCL)
Time-out-Timer (TOT)
PC Programmable
Wired Clone
Selectable Carrier Squelch Level (2 levels: normal or tight)
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Content
1. Function & Feature
2. Technical Specification
3. Software & Setting
4. Disassembly & Re-assembly
5. Circuit Description & Analysis
6. Trouble Shooting
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2. Technical Specification
Testing Specifications
RX
General
≤0.224μV
Sensitivity
400-420MHz, 450-470MHz
Freq. Range
136-154MHz, 146-174MHz
Channel Capacity
16
Channel Space
25KHz/ 12.5KHz*
Working Voltage
7.4V DC
Battery Capacity
1300mAh (Li-ion)
Adjacent Channel
Selectivity
Intermodulation
60dB
Spurious
Response
65dB
Rejection
Rated
Audio 0.5W (SPK impedance is
Power
Working Time (5-5-90)
> 11 hours
Rated
16 ohm)
Audio
Distortion
Working Temperature
Frequency Stability
TX
RF Power Output
(with battery, without antenna)
antenna
≤5%（0.5W）
-25℃~+60℃
Dimensions（H×W×D）
Weight (with battery and
65dB
113mmx 54mmx35mm
Spurious
4W/ 2W
and
Harmonics
250g
±2.5ppm
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≤-26dBm
Modulation Limiting
≤5KHz
FM Noise
≥40dB
Audio Distortion
≤5%
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2. Technical Specification
CV Testing and Adjust
CV voltage
High Freq.
Low Freq.
RX TC101
3～4V
≥0.5V
TX TC101
3～4V
≥0.5V
TC101
Notice
RX and TX use the same VCO. When
adjusting TC101, we need check TX and RX
CV Testing Point
CV voltage at same time.
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2. Technical Specification
Status Indication
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2. Technical Specification
Status Indication
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Content
1. Function & Feature
2. Technical Specification
3. Software & Setting
4. Disassembly & Re-assembly
5. Circuit Description & Analysis
6. Trouble Shooting
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3. Software & Setting
Programming Software
Now, please open the programming software.
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3. Software & Setting
Software Adjustment
Please do not tune these items if not repairing/testing necessary.
We can enter Tuning Mode by Programming Software.
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Content
1. Function & Feature
2. Technical Specification
3. Software & Setting
4. Disassembly & Re-assembly
5. Circuit Description & Analysis
6. Trouble Shooting
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4. Disassembly & Re-assembly
Disassembly steps as following:
1. Turn the radio off
2
2. Remove antenna, channel selector knob, channel
3
4
switch knob. (1,2,3)
3. Remove the fixed screws. (4,5)
4. Lift the chassis by its bottom and pull it out of the
radio case.
1
5
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4. Disassembly & Re-assembly
5. Remove the fixed screws on the PCB and side PTT board
6. Remove the antenna terminal with soldering
7. Lift the PCB and remove it from the chassis.
The Re-assembly method is similar and reverse the steps.
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Content
1. Function & Feature
2. Technical Specification
3. Software & Setting
4. Disassembly & Re-assembly
5. Circuit Description & Analysis
6. Trouble Shooting
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5. Circuit Description & Analysis
The Circuit including:
The general circuit is composed of TX circuit, RX circuit, power
supply circuit, control circuit and etc.
1. RF parts: RX, TX
2. FGU: PLL and VCO
3. Control Circuit: power supply and CPU
4. Baseband
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5. Circuit Description & Analysis
Block Diagram
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5. Circuit Description & Analysis
MCU Control, Signal Processing and Audio Power Amplification
MIC
B201
2
SP_JACK
J3
PJ-D3027D
2
AF
1
AF AMP
U302
MICJACK
AF_SW
Q302
SW
VOLUME
S201
LED
D601
VOX_DET
Q611
D616
BATTERY
G602
QT_OUT
R204
C204
C205
MODE_OUT
RXD
AF_MODULATING
FILLER
TXD
EC0/EC1/EC2/EC3
RESET IC
U605
RESET
E2ROM
U603
SDA/SCL
DATA/STB/CK
U601
MCU
SRT3210
PTT/SK1/SK2
LD
W/N
APC
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TX_CTL
SAVE
T/R
RF_MUTE
SW_CHANNAL
MODE
AF_MUTE
BEEP
BEEP
QT_MODULATING
FILLER
R607
R632
R206
T_LED
R_LED
QT_OUT
MIC IN
LED
D602
VOX
1
SPK
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5. Circuit Description & Analysis
MCU Control, Signal Processing and Audio Power Amplification
1) MCU Control Circuit
MCU control circuit is composed of MCU, EEPROM, and keys, etc. This section has
the following functions: to initialize data of the radio and save data to EEPROM; to
detect battery voltage and signals from external keys, LD and VOX, and to make
response; to transmit required data to PLL based on the channel encoding status; to
switch and control RX/TX based on the input PTT signal; to switch the squelch circuit
on/off based on the input signaling decode signal and squelch level signal; to control
circuits of high/low power switch, audio power amplifier, VCO power supply, RX power
supply and TX power supply; (for programming) to communicate with PC via RXD/TXD
based on the RS232 protocol, and transmit/receive data to/from PC.
2) Signal Processing Circuit
a. TX Baseband Processing
The audio signals input from MIC are divided into two parts. One part enters U601,
and is then converted into digital signal by analog-to-digital conversion (ADC).
Afterwards, the converted signal will go through a series of processing including lowpass filtering, AGC, companding, high-pass filtering, encrypting and pre-emphasizing,
and then it will be output as baseband signal after digital-to-analog conversion (DAC).
The baseband signal is processed by the active low-pass filter and then sent to VCO
for modulation; for the other part, it will go through VOX circuit (Q611 and D616) and
then sent to MCU for VOX processing.
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5. Circuit Description & Analysis
MCU Control, Signal Processing and Audio Power Amplification
b. RX Baseband Process
The demodulated IF signals with CTCSS/CDCSS signaling enter U601 for decoding.
After analog-to-digital conversion, the IF signals will be converted into digital signals,
which go to low-pass filter for filtering and then are divided into two parts. One part is
processed by CTCSS/CDCSS decoder, and the other is processed by high-pass filter
and then is subject to de-emphasis, decryption, signal expansion etc, and finally
digital-to-analog conversion to output audio signal.
3) Audio Power Amplifier
The audio signal output from U601 is amplified by the audio power amplifier (U302) to
drive the speaker directly.
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5. Circuit Description & Analysis
MCU&Power
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5. Circuit Description & Analysis
MCU&Power
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5. Circuit Description & Analysis
AF AMP and Speaker/MIC interface
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5. Circuit Description & Analysis
The 7.4V battery voltage is converted
to 5V via DC-DC module U604, and
further converted via LDO U602 to 3V
VR SW
Q604
Q305
VR
TX_CTL
SAVE
RF_MUTE
Power supply
LDO
U606
VT
including two channels: VCC and VDD.
VCC powers CPU and VDD powers
PLL circuit. The 5V voltage will be
V_SAVE
converted via LDO U606 to 4.5V
VCC
LDO
U602
VDD
LDO
U604
including two channels: VT and VSAVE. V-SAVE powers VCO circuit
5V
and VT powers TX circuit. Finally, VSAVE controlled by Q604 and Q305
V_BAT
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outputs VR, which supplies RX circuit.
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5. Circuit Description & Analysis
Power supply
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5. Circuit Description & Analysis
PLL&VCO
PLL Frequency Synthesizer
The PLL circuit mainly provides the first local oscillator signal (for RX) and RF
carrier signal (for TX). It is composed of VCO and PLL chip, allowing frequency
tracking and channel switching under the control of MCU signals.
LOCAL OSCILLATOR AMP
Q104
2SC5108
BUFFER AMP
Q105
2SC4226
T/R
T/R SW
Q103
D105
PLL
LOOP FILTER
U601
MCU
SRT3210
DATA/STB/CK
LD
PLL
U102
MB15E03SL
CP
TX/RX
VCO
Q102
MODE
3
Crystal
XT 101
38.4MHz2
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VDD
4
1
QT_MODE
FILLER
R103
C132
QT_OUT
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5. Circuit Description & Analysis
PLL&VCO
1) PLL
The step frequency of PLL circuit is 5 KHz or 6.25 KHz. In U101, the 38.4MHz reference
oscillator signal is divided into 5 KHz or 6.25 KHz reference frequency via a fixed counter
in PLL. The signal from VCO enters the PLL after processed by the buffer amplifier, and
then it is applied to the variable frequency divider in PLL for division. After division, the
signal is compared with the reference frequency at the phase detector (PD) in PLL. The
signal from the PD passes through a low-pass filter and then is applied to the varactors
(D101 and D102) of VCO to control the output frequency. Then the RF signal is
processed by the buffer amplifiers (Q104 and Q406), and controlled by D404 and D405
to only serve as TX signal or RX first local oscillator signal.
2) VCO
The VCO section is realized by the three-point capacitor oscillator circuit. TX VCO and
RX VCO share the same oscillator circuit. Q103 controls the switch between TX VCO
and RX VCO.
Note: If the PLL is unlocked, the LD pin of U101 outputs low level. If the
microprocessor detects such situation, TX/RX operation is prohibited, and an
alarm sounds.
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5. Circuit Description & Analysis
PLL&RX
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5. Circuit Description & Analysis
PLL and 38.4MHz Ref. Crystal
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5. Circuit Description & Analysis
TX&VCO
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5. Circuit Description & Analysis
VCO
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5. Circuit Description & Analysis
TX
The audio signal from MIC is sent to the MCU chip (U601) directly. The
baseband signal processing circuit in U601 converts the amplified audio signal to
digital signal via A/D conversion, and then converts the digital signal to analog
audio signal via D/A conversion after all processing procedures such as filtering,
signal compression, encryption, pre-emphasis, TX gain control and amplitude
limiting are completed. Then the analog audio signal from MCU passes through
the low-pass filter circuit and directly goes to VCO for frequency modulation. The
modulated HF carrier signal passes through the buffer amplifiers (Q104 and
Q406), and goes to the amplifier (Q401) through the RF switch (D404). Then the
amplified RF signal enters the low-pass filter circuit after it is further amplified by
the pre-driver (Q402) and final-stage power amplifier (Q403), and then it will be
finally transmitted via antenna after ultra harmonics is removed.
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5. Circuit Description & Analysis
TX
LO
LOCAL OSCILLATOR AMP
Q406
2SC4226
VR SW
D405 POWER AMP
Q401
2SC4226
VT SW
D404
POWER AMP
Q402
RD01
POWER AMP
Q403
RD07
POWER
MATCH
VT
LOCAL OSCILLATOR AMP
Q104
2SC5108
T/R
APC_SW
Q404
DTC114YE
T/R SW
Q103
D105
VT
TX/RX
VCO
Q102
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APC
U401
SW
Q405
DTC114EE
APC
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ANT LPF
5. Circuit Description & Analysis
RF power amplifier
The modulated carrier signal from VCO is pre-amplified
at Q104 and Q406, and controlled at D404 and D405.
Then it is amplified by the front-stage amplifier Q401,
the pre-driver Q402 and the final-stage amplifier Q403
orderly. Finally it goes to the LC low-pass filter (LPF)
and is transmitted from the antenna after high-order
harmonics are removed by LPF.
APC circuit is composed of Q404, Q405 and U401.
U401 controls the bias voltage at the gates of Q402 and
Q403, to control TX current and to further regulate
power.
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5. Circuit Description & Analysis
TX/RX switch and RF LPF
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5. Circuit Description & Analysis
RF AMP and TX final AMP
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5. Circuit Description & Analysis
Current detect and APC
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5. Circuit Description & Analysis
RX
After the RF signals are received from the antenna, the undesired out-of-band
signals are filtered out at the bandpass filter. Then the remaining RF signals
are amplified by LNA Q501. Afterwards, the amplified signal goes through the
bandpass filter again to eliminate undesired out-of-band interference signal.
After being filtered and amplified, the RF signals and first LO signals are mixed
at Q502, and then the mixed signal is filtered by crystal filter XF501 to get
38.85MHz differential signals as the first IF signal.
After being amplified by Q506, the IF signal goes to chip U611, where the
signal will be mixed with the second LO signal (38.4MHZ). Next, the signals will
be filtered by CF501 to produce 450KHz IF signal.
When the IF signals are processed by demodulation circuit (including U611 and
CD501) to generate audio signals, which are delivered to IC Q613 for
amplification and output in two channels. After simple filtering, one channel of
signals is sent to MCU U601 for CTCSS/CDCSS decoding; for the other
channel, it goes through two stages of low-pass filter first, and then it goes to
high-pass filter U610 (consisting of four operational amplifiers) for audio
processing. Finally, the signals will be sent to audio power amplifier U302 for
amplification so as to drive the speaker.
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5. Circuit Description & Analysis
RX
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5. Circuit Description & Analysis
RX LNA and BPF
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5. Circuit Description & Analysis
Mixer and IF filtering and amplifier
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5. Circuit Description & Analysis
IF processing IC, noise selecting freq. and
AF HPF
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5. Circuit Description & Analysis
Level Diagram
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Content
1. Function & Feature
2. Technical Specification
3. Software & Setting
4. Disassembly & Re-assembly
5. Circuit Description & Analysis
6. Trouble Shooting
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6. Trouble Shooting
PCB Top Side
Antenna
Soldering
Point
AF AMP
TDA2822
APC
Circuit
MIC
CPU
Memory
24C16
32.768KHZ
Crystal
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6. Trouble Shooting
PCB Bottom Side
Volume Switch
Channel switch
SPK socket
PTT board
MIC socket
Battery
connector
Power
management IC
Power AMP
RQ0002
38.85MHZ
Crystal Filter
VCO
50C24
PLL IC
MB15E03SL
450
Audio process IC
2902
IF IC:4116
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6. Trouble Shooting
PCB Key Testing Point
External power
supply
connection point
ANT test
point
PTT test
point
BPF test
point
CV test point
LD
checking
point
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6. Trouble Shooting
1. Can not power on
2. Voice abnormal
3. TX problem
4. RX problem
5. Unlock
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6. Trouble Shooting
1. Can’t Power On
Description:
After connecting 7.4V DC voltage, the radio has not any response.
Analysis:
Check power supply circuit and control circuit.
Checking Steps:






Battery connector is connected well with main radio
Power switch
The pin 1 of Regulator IC U604 output is 5V or not
U602 output is 3V or not
CPU power on crystal 32.768KHz
CPU pins is false soldering or broken
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6. Trouble Shooting
1. Can’t Power On
U604
U606
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6. Trouble Shooting
2. Voice Abnormal (no voice when power on; abnormal voice)
Description
No voice or abnormal voice when power on the radio
Analysis
AF output circuit is composed of volume switch S201, AF amplifier
U302 and power supply tube Q303, speaker socket and speaker.
Checking Steps

Speaker, speaker line’s soldering

Speaker socket is connected well or not

Volume switch

AF amplifier IC U302 TDA2822 is
working well or not. Q303 (717) is
damaged or not.
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6. Trouble Shooting
3. TX Problem (No TX power or low power)
Description
After power on, press PTT, LED is red, but no TX power output
or it is low.
Analysis
Check RF AMP and APC circuit. Test TX power supply, Q611/5T,
U430/APC, and test TX power by communication analyzer to
judge which stage has problem.
U606
Checking Steps
 6pin of U606 output voltage is 4.5V or not
 Check TX current, High power is about 1.6A, and 0.8A Low
Power. If normal, that means APC circuit has no problem,
generally, the power amplifier Q403 (RD07) is burnt.
 Check the positive pole of C420 in APC circuit has about
3.5V voltage output, or not
 Check the bias voltage of final power amplifier is normal or
not
 Check driver amplifier and final power amplifier RD07 is
damaged or not
 Test the input pin’s voltage of Q403 is 3-5V while pressing C420
PTT. If not, check the APC circuit.
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RD07
APC
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6. Trouble Shooting
4. RX Problem (Low RX or No RX)
Description
After power on, TX is normal, but, no RX(green led is not on) or
RX sensitivity is low.
Analysis
Check RX filtering circuit or IF processing circuit.
Checking Steps
 VHF/UHF RX sensitivity is 0.25/0.28µV. We use signal
injection to check which stage has problem. The important is
IF AMP and LNA/Mixing circuit. The first IF is 38.85MHz, the
2nd IF is 450kHz.
 Check the carrier squelch level, and CTCSS setting.
 The output voltage of Q604 is 5V or not
 Mixer Q502 is damaged or not
 450kHz filter is loose or damaged or not
 38.85MHz filter is normal or not
 IF processing IC U611 is false soldered or damaged
 Demodulator is loose or damaged or not
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6. Trouble Shooting
5. Unlock
Description
After power on, the radio sounds “Dudu…”. And it can’t
transmit or receive signal.
Analysis:
check RX/TX common circuit and PLL circuit.
Checking Steps:
 Power supply of PLL is 3V or not
 CV voltage is normal or not
 86pin of CPU is normal or not (H:Lock, L:Unlock)
 38.4MHz crystal is normal or not
 IC U101 PLL part is false soldering or damaged
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THANKS
Please call or email Hytera Global Customer Service Center, if you have any
question about Hytera Product.
Service Direct Line:
+86-755-86137081
Email:
overseas.service@hytera.com
Website:
www.hytera.com
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