HYT TC-508 User manual

8130050800200
L07157
2012-08-15

Preface
This manual describes information related with product repair. To repair the product properly, please
read this manual carefully.
This manual is applicable to the following model:
TC-508

Service Manual Contents
i
Contents
1. Introduction ........................................................................................................................................2
2. Product Controls................................................................................................................................3
3. Programmable Key Functions...........................................................................................................4
4. Software Specifications.....................................................................................................................5
5. Circuit Description ...........................................................................................................................11
6. CPU Pins...........................................................................................................................................18
7. Parts List 1........................................................................................................................................21
8. Tuning Description...........................................................................................................................41
9. Troubleshooting Flow Chart............................................................................................................53
10. Disassembly and Assembly..........................................................................................................56
11. Exploded View................................................................................................................................60
12. Parts List 2......................................................................................................................................61
13. Packing Guide ................................................................................................................................62
14. PCB View.........................................................................................................................................63
15. Level Diagram.................................................................................................................................67
16. Block Diagram ................................................................................................................................68
17. Schematic Diagram........................................................................................................................69
18. Specifications.................................................................................................................................75

Introduction Service Manual
2
1. Introduction
Intended User
This manual is intended for use by qualified technicians only.
Safety Information
The following safety precautions shall always be observed during operation, service and repair of this
equipment.
zThis equipment shall be serviced by qualified technicians only.
zUse only our supplied or approved antenna.
zTo avoid electromagnetic interference and/or compatibility conflicts, turn off your radio in any
area where posted notices instruct you to do so. Turn off your radio before boarding an aircraft. Any
use of the radio must be in accordance with airline regulations or crew instructions.
zFor vehicles with an air bag, do not place a radio in the area over an air bag or in the air bag
deployment area.
zTurn off your radio prior to entering any area with explosive and flammable materials.
zDo not charge or replace your battery in a location with explosive and flammable materials.
zTurn off your radio before entering a blasting area.
zDo not use any portable radio that has a damaged antenna. If a damaged antenna comes into
contact with your skin, a minor burn may result.
zDo not expose the radio to direct sunlight for a long time, nor place it close to a heating source.
zWhen you carry a radio with you, please keep its antenna at least 2.5 centimeters away from your
body during transmitting.

Service Manual Product Controls
3
2. Product Controls
No. Part Name No. Part Name
○
1 PTT Key ○ 10 Battery latch
○
2 SK1 (programmable) ○ 11 Accessory Jack Cover
○
3 SK2 (programmable) ○ 12 Accessory Jack
○
4 Antenna ○ 13 Strap Hole
○
5 Channel Selector Knob ○ 14 Belt clip
○
6 Radio On-Off/Volume Control Knob
○
15 Battery
○
7 Speaker Switch ○ 16 Screw for Belt Clip
○
8 Microphone ○ 17 Charging Piece
○
9 LED Indicator / /

Programmable Key Functions Service Manual
4
3. Programmable Key Functions
For enhanced convenience, you may request your dealer to program the keys SK1 and SK2 as
shortcuts to the functions listed below:
No. Shortcut Key Function
1 Adjusting the Power Level To adjust power level quickly.
2 Battery Strength Indicator To show the remaining battery strength
3 Channel Lock
To lock the channel which would disable the Channel Selector
knob.
4 Monitor Button
To adjust the condition for incoming signal match
5 Monitor Momentary
6 Squelch Off To always unmute speaker no matter whether carrier is present
or not
7 Squelch Off Momentary
8 Scanning To receive signals on other channels
9 VOX To make the radio transmit automatically when you speak.

Service Manual Software Specifications
5
4. Software Specifications
4.1 Status Indication
See the table below for LED and alert tone indications:
Item Indication
Wired
Clone
To enter Wired Clone Mode
zturn on the source radio with SK1
held down for approximately 2
seconds;
zTarget radio: turn it on directly.
The LED on the source radio flashes red once during
the power-on process.
Status of the source radio in Wired
Clone Mode
(After the target radio is turned on
and the cloning cable is connected,
press the PTT key of the source radio
to begin cloning.)
The LED glows red during cloning process.
Error occurs during cloning:
zUser Clone Mode: At the start of cloning,
frequency band and Model ID will be checked.
The LED glows orange for 2 seconds and then
goes out to indicate a failed check. If the check is
successfully carried out but error occurs during
cloning, the LED will flash orange. In this
situation, press any key to make it go out.
zFactory Clone Mode: The LED flashes orange in
presence of error. Press any key to make it go
out.
The LED glows green once cloning is completed.
Status of the target radio in Wired
Clone Mode
The LED glows green during cloning.
The green LED goes out after cloning is completed.
Power On (to enter User Mode)
When the radio is turned on, a power-on alert tone
sounds.
When the radio is currently on a blank channel, it
sounds beep tones continuously.
Low Battery Alert
The LED flashes red, and the low-pitched tone
sounds every 20 seconds (programmable by the
dealer).

Software Specifications Service Manual
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Item Indication
Transmitting
zThe LED glows red during transmitting.
zWhen TOT timer expires, the radio sounds beep
tone continuously.
zA TOT pre-alert tone sounds before the TOT
timer expires.
Receiving The LED glows green during receiving.
Scanning
zThe LED flashes green once per second during
scanning.
zScan Start Alert (programmable by the dealer):
one beep will sound.
zScan End Alert (programmable by the dealer):
two continuous beeps will sound.
Writing/Reading
The LED glows red when the PC is reading data
from the radio.
The LED glows green when the PC is writing data
into the radio.
Power Adjustment
A low-pitched tone sounds when the radio switches
from high power to low power.
A high-pitched tone sounds when the radio switches
from low power to high power.
VOX/Channel Lock
One audio alert for enabling;
Two audio alerts for disabling;

Service Manual Software Specifications
7
4.2 Function List
zChannel Capacity: 16
zChannel Spacing: 25KHz/12.5KHz
zChannel Scan
zRX/TX status indication (red/green LED)
zCTCSS/CDCSS (38 groups of CTCSS, 83 groups of CDCSS, and CTCSS Tail Invert by 180
degrees.)
zLow battery alert
zBattery Save
zUnlock Detection and Emergency Alarm
z2 Selectable Squelch Levels
zMonitor Button
zTime-out Timer (TOT)
zSquelch Tail Elimination
zPC Programming (manual/ automatic tuning)
zHigh/Low Power Switch (4.0/ 2.0W)
zWide & Narrow Bandwidth Compatibility*
zBusy Channel Lockout (transmission prohibited in busy status)
zWired Clone
zBattery Strength Indicator
zManual Tuning
zVOX and 5 Selectable Sensitivity Levels
Note
* indicates optional functions.
4.3 Description of Modes
4.3.1 User Mode
It is a conventional communication mode. The radio will enter this mode by default after power-on.
4.3.2 PC Programming Mode
The radio in User Mode enters PC Programming Mode through specific protocol based

Software Specifications Service Manual
8
communication with the programming software. In this mode, radio functions and adjustment parameters
can be set through the programming software (including User Version and Factory Version).
4.3.3 Wired Clone Mode
Description
Wired Clone Mode is an independent mode. To access other modes, you must restart the radio.
Wired Clone Mode includes Clone Mode and Factory Clone Mode.
1) User Clone Mode:
Connect two radios using a cloning cable. Power on the source radio while holding down SK1; the
radio will enter Clone Mode in approximately 2 seconds. Then directly power on the target radio to enter
the User Mode. In this mode, data stored in EEPROM of the source radio will be cloned to EEPROM of
the target radio. The data transferred only involves channel data and common parameters, excluding
tuning data, version and serial No. of the model.
2) Factory Clone Mode:
Connect two radios using a clone cable. Hold down both SK1 and Power On/Off Key of the source
radio, it will be turned on and will enter User Clone Mode by default after 2 seconds. Press SK
afterwards to switch to Factory Clone Mode. The target radio can be directly turned on to enter user
mode. The data transferred covers all data in EEPROM (including settings for the Manual Tune Switch),
other than the serial No.
Process
Step 1 The LED flashes red once after the source radio enters the Wired Clone Mode. Press PTT to
begin to clone data to the target radio.
Step 2 During cloning, LED of the source radio solidly glows red, and LED of the target radio solidly
glows green. When cloning is completed, LED of the source radio solidly glows green, and the
green LED of the target radio goes out, which indicates the preparation for another clone.
Step 3 If any abnormal situation occurs during cloning, the source radio will stop cloning and its
LED will flash orange, which indicates the preparation for another clone.
Step 4 When cloning is completed, the source radio goes back to standby status. Press PTT again to
begin another clone.
4.3.4 Manual Tune Mode
In this mode, you can manually tune the frequency deviation, power level and squelch level and etc.
Description of Tuning:

Service Manual Software Specifications
9
To enter Manual Tune Mode
Hold down the PTT and SK1 key for 2 seconds while powering on the radio. The LED glows orange to
indicate that the radio has entered the Manual Tune Mode. When the keys are released, the radio will
enter item N of Tx group (N depends on the position where the Channel Selector Knob locates).
Note
To enter the Manual Tune Mode, make sure its switch is set to Open via the programming software. If
this option is unchecked, the radio can not enter this mode, which helps avoid change of parameters
and degradation of radio performance caused by user’s misoperations.) Keep this option unchecked
after values are well adjusted from factory, to avoid any unexpected change of values. Such values
can only be reset and changed in Manual Tune Mode only.
To switch between TX tuning items and RX tuning items
Rotate the Channel Selector knob to switch between TX tuning items and RX tuning items.
The LED glows red for TX tuning items and green for RX tuning items.
zTX group: CH1-CH9 respectively stands for TX Low Power, TX High Power, CDCSS Balance,
CDCSS Deviation, CTCSS Deviation (low), CTCSS Deviation (medium), CTCSS Deviation (high),
TX Low Voltage Threshold and Max. TX Audio Deviation.
The LED solidly glows red during TX group tuning (CH1 to CH9).
zRX group: CH10-CH13 respectively stands for SQL Normal Open, SQL Normal Close, Rx Low
Voltage Threshold and Bandpass Filter.
The LED solidly glows green during RX group tuning (CH10 to CH13).
CH14 to CH16 are unavailable and LED will go out.
To switch between wide and narrow bands *
Under a certain tuning item, long press the PTT key (the LED flashes orange to indicate valid press) to
switch between wide and narrow bands. After the band is selected, the first frequency of the current
band is the frequency for tuning by default.
To switch the frequency
Under a certain band, short press the PTT key (the LED flashes green to indicate valid press) to switch
the frequency orderly.
To tune the value
Under a certain band, short press SK1 to increase the value in step of 1, or hold this key to increase the
value continuously in steps of 1. The value will remain unchanged once it reaches the allowed maximum
value.

Software Specifications Service Manual
10
Short press the SK2 key to decrease the value in step of 1, or hold down this key to decrease the value
continuously in steps of 1. The value will remain unchanged once it reaches the allowed minimum value.
About several special items
zTX group: CH8 (TX Low Voltage Threshold) which is related to AD sampling. Press the SK1 or SK2
key after entering the above item, to activate AD sampling (including calculation) once. Rotate the
Channel Selector knob to save the current AD sampling value.
zRX group: CH10 to CH12 represent SQL Normal Open, SQL Normal Close and RX Low Voltage
Threshold respectively. These items are related to AD sampling. Press the SK1 or SK2 key after
entering the above items, to activate AD sampling (including calculation) once. Rotate the Channel
Selector knob to save the current AD sampling value.
About the key-press
zShort press: key-press time shorter than 1 second;
zLong press: key-press time longer than 1 second.

Service Manual Circuit Description
11
5. Circuit Description
5.1 General Principle Diagram
The general circuit is composed of RDA chip circuit, TX circuit, RX circuit, power supply circuit, control
circuit, etc. See the block diagram below:
Swich
Q409
Q408
U622
MCU
MC9S08AC60
MICJACK
SW_CHANNAL
E2ROM
U603
LDO
U619
LDO
U621
V_BAT
PWER
SDA/SCL
RESET
EN0/EN1/EN2/EN3
AF
VOX_DET
1
2
PTT/SK1/SK2
MICIN
VCC
VDD
R_LED
LED
D601
LED
D602
RXD
TXD
SP_JACK
J3
PJ-D3027D
1
2
MIC
B201
BATTERY
G602
5V
BEEP
VT
TX_EN
CSS/CODE/INT/SDO
/RXON/TXON/SQ/PDN
SDIO/SCLK/SEBN/PDN
AF
EXT_PTT
/EXT_MIC
VT
LNA
Q501
AT41511
PA
Q407
2SC3356
BIAS DOWN
PA
Q402
RD01
PA
Q403
RD07
ANT LPF
APC
U401
APC
BAT
VT
RFOUT
5V
RX_EN
BPF1
VRCR
1
3
2
4
VDD
DSP
DAC/ADC
Synthesize r
VT
AF AMP
U302
D401 D402
SPK
BAT
VOX_DET
U613
D656
U101
RDA1846
RDA Circuit: This chip is highly integrated. Its function includes voice signal
processing/modulation/demodulation, DSP, VCO, PLL, LNA and RF IF. The voice signal from MIC goes
to RDA chip for amplification. Next, the amplified voice signal will undergo a series of processing
including A/D conversion, filtering, pre-emphasizing, gain control, amplitude limit and D/A conversion.
Then the analog voice signal is delivered to VCO and amplified to a signal with 8dBm. When the RX RF
signal enters this chip, it would experience demodulation, filtering, de-emphasizing and gain control.
Finally, the signal is output to the audio amplifier.
zTX section: The modulated RF signal from RDA chip goes to Q407 and Q402 for amplification, and
then further amplified by Q403. Then the amplified signal is delivered to low-pass filter to filter out the
high-order harmonics. Finally, it is sent via the antenna.
zRX section: After going through LPF and amplitude limiter, the RF signal received from the antenna
enters Q501 LNA for amplification. Then the BPF will filter the signal to remove other unwanted

Circuit Description Service Manual
12
signals. The resulting signal is delivered to RDA chip for demodulation. After that, the voice signal
from demodulation is output U302 for amplification, which is finally output from the speaker.
zLDO U619 converts the 7.4V power supply into two 5V, which LDO U621 will convert into two 3.3v
power supplies, powering VCC and VDD respectively. VCC powers CPU, while VDD powers RDA
chip. Then Q406 converts the 5V power supply to VT to power the TX circuit.
5.2 Realization Methods of Basic Functional Modules
5.2.1 RDA Chip Circuit
This chip is highly integrated. Its function includes voice signal
processing/modulation/demodulation, DSP, VCO, PLL, LNA and RF IF.
RDA Chip Circuit
VRCR
1
3
2
4
VDD
DSP
DAC/ADC
U101
RDA1846
The reference clock signal of RDA chip is provided by 26MHZ crystal oscillator. The block diagram is
given below:

Service Manual Circuit Description
13
After entering RDA chip via MIC, the voice signal will undergo A/D conversion to get digital
signal, which will be delivered to DSP for further processing such as filtering, amplification,
amplitude-limiting and pre-emphasizing. Then the resulting voice signal is modulated to the internal VCO
and output after being amplified by the driver amplifier. At the RX end, the received RF signal will go to
LNA for amplification first, and then go to IF demodulation circuit to get demodulated voice signal. After
gain control, such signal is converted into digital signal, which will enter DSP for further processing such
as filtering, amplification and de-emphasizing.
The function of RDA is subject to MCU U622 and its reference clock signal is from 26MHZ crystal
oscillator. This chip is applicable to UHF (400~520MHZ) and VHF (134~174MHZ). The NF can be up to
3dB and IIP3 up to -6dBm, meeting GB and FCC requirements. Its RF output may reach up to 8dBm.
RF Power Amplifier Circuit (TX Section)
The block diagram of the RF power amplifier circuit is shown in the figure below:

Circuit Description Service Manual
14
The modulated RF signal from RDA chip goes to Q407 and Q402 for amplification, and then further
amplified by Q403. Then the amplified signal is delivered to low-pass filter to filter out the high-order
harmonics. Finally, it is sent via the antenna. The control signal “VT” is used to control the operation of
driver amplifier (Q407 and Q402). U401 works for auto power control (APC).
Receiver Circuit (RX Section)
The Block Diagram of RX Circuit is shown as below:

Service Manual Circuit Description
15
LNA
Q501
AT41511
ANT LPF
5V
RX_EN
BPF1
VT
D401 D402
The RF signal is received via the antenna. After going through LPF and amplitude limiter, the signal is
amplified by Q501 LNA. The LNA adopts 2SC3356 with current <5mA and its gain is about 12dB.
Next, the BPF will remove the interference signal in amplified RF signal. Then the resulting signal goes
to RDA chip for further processing. The processed signal is delivered to U302 for amplification and finally
output by the speaker.
MCU Control, Signal Processing and Audio Amplification
Circuit diagram of this section is shown as below:

Circuit Description Service Manual
16
U622
MCU
MC9S08AC60
MICJACK
E2ROM
U603 SDA/SCL
RESET
EN0/EN1/EN2/EN3
AF
1
2
PTT/SK1/SK2
LED
D601
LED
D602
RXD
TXD
SP_JACK
J3
PJ-D3027D
1
2
MIC
B201
BATTERY
G602
CSS/CODE/INT/SDO
/RXON/TXON/SQ/PDN
SDIO/SCLK/SEBN/PDN
EXT_PTT
/EXT_MIC
AF AMP
U302
SPK
BAT
VOX_DET
U613
D656
MCU Control Circuit
MCU control circuit is composed of MCU, EEPROM, 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, RDA chip power supply, RX power supply and

Service Manual Circuit Description
17
TX power supply; (for programming) to communicate with PC via RXD/TXD based on the RS232
protocol, and transmit/receive data to/from PC.
RDA Chip Control
By controlling the RDA chip, the MCU can realize these services: frequency setting, frequency
bandwidth, reference clock, sleep mode, SQ, VOX, squelch, frequency deviation, voice filtering,
signaling encoding/decoding, pre-emphasizing, gain control, amplitude limiting, de-emphasizing, etc.
Audio Amplifier
The audio signal output from U622 is amplified by the audio power amplifier (U302) to drive the speaker
directly.
Power Supply Section
Block diagram of power supply circuit is shown as below:
Swich
Q409
Q408
LDO
U619
LDO
U621
V_BAT
PWER
VCC
VDD
5V
VT
TX_EN
LDO U619 converts the 7.4V power supply into two 5V, which LDO U621 will convert into two 3.3v
power supplies, powering VCC and VDD respectively. VCC powers CPU, while VDD powers RDA chip.
Then Q406 converts the 5V power supply to VT to power the TX circuit.

CPU Pins Service Manual
18
6. CPU Pins
Pin No. Port Name Pin Name Port
I/O Function
1 PTC4 Reserved I Reserved
2 IRQ/TPMCLK Reserved I Reserved
3 RESET RESET I Reset
4 PTF0/TPM1CH2 BEEP O Tone
5 PTF1/TPM1CH3 VRCR O PWM output for frequency adjustment
6 PTF2/TPM1CH4 APC O PWM output for PA APC
7 PTF3/TPM1CH5 CSS I Detection pin, CDCSS status output
8 PTF4/TPM2CH0 TXON I TX status detection pin
9 PTC6 PWER O Radio power control pin
10 PTF7 Reserved I Reserved
11 PTF5/TPM2CH1 RXON I RX status detection pin
12 PTF6 Reserved I Reserved
13 PTE0/TxD1
UART_TX
D
O Port
14 PTE1/RxD1
UART_RX
D
I Port
15 PTE2/TPM1CH0 INT I Detection pin, programmable
16 PTE3/TPM1CH1 CODE I/O
Detection pin, modulated digital signal
input/output
17 PTE4/SS1 SEBN O SPI port of communication
18 PTE5/MISO1 SDO I SPI port of communication
19 PTE6/MOSI1 SDIO O SPI port of communication
20 PTE7/SPSCK1 SCLK O SPI port of communication
21 VSS VSS / Ground