HYT TC-268 User manual

www hyt com cn.. .

TC-268/368 Service Manual
1
Contents
General ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．2
Brief Introduction ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
．．．．．．．．．．3
Software Description ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．4
Circuit Description ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
．．．．．．．9
TC-268 Parts List 1 ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．15
TC-368 Parts List 1．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
．．．．．43
Adjustment Description．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．57
Disassembly．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
．．．．．61
Exploded View．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．62
Parts List 2．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
．．．．．．．．．．．．．．．63
Packing．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．65
TC-268 PC Board View ．．．．．．．．．．．．．．．．．．．．．．．．
．．．．．．．．．．．．．．．．．．．．66
TC-368 PC Board View．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．68
TC-268 Level Diagram．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
．．．．．．．．．．．．．70
TC-368 Level Diagram．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．71
TC-268 Block Diagram．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
．．．．．．72
TC-368 Block Diagram．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．73
TC-268 Schematic Diagram．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．74
TC-368 Schematic Diagram．．．．
．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．75
Specifications．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．76

TC-268/368 Service Manual
2
General
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.
User Safety Information
The following precautions are recommended for personnel safety:
zDO NOT operate the transmitter of radio unless all RF connectors are secure and any open
connectors are properly terminated.
zSHUT OFF and do not operate this equipment near electrical blasting caps or in an explosive
atmosphere.
zWhen in vehicles with an airbag, do not place a portable radio in the area over an airbag or in the
airbag deployment area.
zDo not expose the radio to direct sunlight for a long time nor place it close to a heating source.
zDo not use any portable radio with a damaged antenna. If a damaged antenna comes into contact
with your skin, a minor burn may result.
zWhen transmitting with a portable radio, hold the radio in a vertical position with its microphone
about 5 centimeters away from your mouth.
zIf you wear a portable radio on your body, be sure to keep the antenna at least 2.5 centimeters
away from your head or body when transmitting.
zThis equipment should be serviced by a qualified technician only.
Shenzhen HYT Science and Technology Co., Ltd. reserves the right to change the data contained in
this manual without prior notice.

TC-268/368 Service Manual
3
Brief Introduction
1. Mode
User mode: Turn on the power to enter.
PC mode：Configure and adjust the radio data via PC software or programmer.
2. Parts description:
(1) Antenna
(2) Channel (frequency) selector knob
Turn the knob to select channel from 1~16(channel 16 may be programmed by your dealer as scan
channel).
(3) LED indicator
Red LED lights up while transmitting, green LED lights up while receiving a signal. LED flashes red
if the battery voltage goes low while transmitting.
(4) Power /Volume control knob
Rotate the knob clockwise to turn on the radio, anti-clockwise till a “click” is heard to turn off the
radio. When power on, rotate the knob to adjust the volume level.
(5) Speaker
(6) Microphone
(7) PTT switch (push to talk)
Hold down the PTT and speak into the microphone to transmit; Release the PTT to receive.
(8) Monitor key
Press the monitor key to open squelch; release to close squelch.
(9) Speaker/microphone jack
(10) Belt clip
(11) Battery

TC-268/368 Service Manual
4
Software Description
I．Specifications:
1. Use mechanical knob to choose from 16 channels.
Frequency: VHF: 136~150MHz VHF: 150~174MHz
UHF: 400~420MHz UHF: 450~470MHz
2. Monitor
3. Battery save
4. Audio alarm
5. Auto squelch control (0~9 level)
6. Time-out Timer (TOT)
7. Channel spacing 25kHz/12.5kHz (Wide/Narrow)
8. CTCSS, CDCSS and TTS encode
9. CTCSS, CDCSS and TTS decode
10.Busy channel lockout
11.Clock frequency deviation
12.Scan
13.PC mode
14.PC tuning mode
15.Wired clone
16.Manual adjusting mode
II．Description:
1. User mode: normal communication mode
2. PC mode:
The following parameters can be set via external programmer or PC programming software:
(1) Receive frequency & Transmit frequency
(2) Receive signaling & Transmit signaling
(3) Busy channel lockout
(4) Clock frequency deviation
(5) Time-out Timer (TOT)
(6) Squelch level
(7) Battery save
(8) Audio Alarm
(9) Channel space 25kHz/12.5kHz(Wide/Narrow)
(10) Monitor mode
(11) Scan mode
(12) Revert channel
(13) Priority channel

TC-268/368 Service Manual
5
3. PC tuning mode:
The following parameters can be set via external programmer or PC programming software:
(1) Frequency stability
(2) RF power
(3) Low battery alert
(4) Squelch (level 9 and level 3)
(5) CTCSS deviation (Wide/Narrow).
(6) CDCSS deviation (Wide/Narrow).
(7) Receive sensitivity (Low/Medium/High)
4. Wired Clone:
Power on the radio via holding down the MONI key, then the radio enters the wired clone mode
2 seconds later, press PTT to begin cloning while red LED flashes, red LED goes out while
cloning is finished.
5. Mode setting:
(1) Short circuit the two SELF points (short circuit) on PCB, and turn on the radio, two
“Beeps” are heard.
(2) Turn channel selector knob to corresponding channel (1-16) according to the model
(see initial data table)
(3) Press [PTT] while holding down [MONI] to set the mode. Channel data and settings
are initialized.
(4) Turn off the radio, disconnect the two SELF points on PCB to end mode settings.
Take TC-268(2) for example, its number is 2, to initialize its model and channel data: Short
circuit the two SELF points on PCB , and turn on the radio, set the channel selector knob at
CH2, and then press PTT while holding down MONI, channel data of CH1,CH2,CH3 and
CH4 is initialized as the corresponding data of No.2. Reset data to initial data. The receive
and transmit frequency of channel 5-14 are the same with channel 1, signallings are 5,
10:67.0Hz; 6,11:151.4Hz; 7,12:250.3Hz; 8,13:423(CDCSS); 9,14: -423(CDCSS), Channel
1-9 are Wide, Channel 10-14 are Narrow. Turn off the radio after reset, disconnecting SELF
and re-power on to use the radio.
(5) Remarks:
The former data (frequency, CTCSS/CDCSS, channel function settings) will be deleted once
the new model is set, and some functions will also be changed. Therefore, do not make this
operation unless necessary, such as replacing the EEPROM, etc.

TC-268/368 Service Manual
6
(6) TC-268/368 channel frequency table (after setting):
1CH 2CH(Medium) 3CH(Low) 4CH(High)
No Model Frequency(MHz) Initial
(MHz) IF(MHz) Tx(MHz) Rx(MHz) Tx(MHz) Rx(MHz) Tx(MHz) Rx(MHz) Tx(MHz) Rx(MHz)
1 TC-268(1) 136.000~149.995 140.000 +38.85 143.100 143.100 143.000 143.100 136.000 136.100 149.975 149.900
2 TC-268(2) 150.000~173.995 150.000 +38.85 162.100 162.100 162.000 162.100 150.000 150.100 173.975 173.900
3 TC-368(1) 400.000~419.995 410.000 -38.85 410.100 410.100 410.000 410.100 400.000 400.100 419.975 419.900
4 TC-368(2) 450.000~469.995 450.000 -38.85 460.100 460.100 460.000 460.100 450.000 450.100 469.975 469.900
5 350.000~369.995 360.000 -38.85 360.100 360.100 360.000 360.100 350.000 350.100 369.975 369.900
6 370.000~389.995 380.000 -38.85 380.100 380.100 380.000 380.100 370.000 370.100 389.975 389.900
7 220.000~239.995 230.000 -38.85 230.100 230.100 230.000 230.100 220.000 220.100 239.975 239.900
8 240.000~259.995 250.000 -38.85 250.100 250.100 250.000 250.100 240.000 240.100 259.975 259.900
9 406.000~429.995 410.000 -38.85 418.100 418.100 418.000 418.100 406.000 406.100 429.975 429.900
10 144.000~147.995 145.000 +38.85 146.100 146.100 146.000 146.100 144.000 144.100 147.975 147.900
11 336.000~367.995 350.000 -38.85 352.100 352.100 352.000 352.100 336.000 336.100 367.975 367.900
12 268.000~395.995 380.000 -38.85 382.100 382.100 382.000 382.100 268.000 268.100 395.975 395.900
13 430.000~439.995 430.000 -38.85 435.100 435.100 435.000 435.100 430.000 430.100 439.975 439.900
14 438.000~449.995 440.000 -38.85 444.100 444.100 444.000 444.100 438.000 438.100 449.975 449.900
15 465.000~494.995 480.000 -38.85 480.100 480.100 480.000 480.100 465.000 465.100 494.975 494.900
16 490.000~519.995 500.000 -38.85 505.100 505.100 505.000 505.100 490.000 490.100 519.975 519.900
Initialization data of channel are in the above table CH1-CH4, the modify frequency is reset to initial data. Frequency on CH5~CH14 are the same with CH1.
The signaling of CH5 and CH10 is 67.0Hz; the signaling of CH6 and CH11 is 151.4Hz; the signaling of CH7, CH12 is 250.3Hz; the signaling of CH8 and
CH13 is 423(CDCSS); the signaling of CH9 and CH14 is -423(CDCSS). CH1~CH9 are Wide, CH10~CH14 are Narrow.

TC-268/368 Service Manual
7
6. Manual Adjusting Mode:
Press PTT and MONI simultaneously to turn on the radio，enter manual Adjusting mode 3
seconds later. Choose the settings by turning the channel selector knob CH1-12, use PTT
(upward) or MONI (downward) to adjust (Notice: MIC jack shouldn’t be connected with external
cable while adjusting), CH 1~12 are defined as follows:
(1) Frequency stability
(2) RF power
(3) Low battery alert
(4) Receiver sensitivity (adjust at medium frequency)
(5) Receiver sensitivity (adjust at low frequency)
(6) Receiver sensitivity (adjust at high frequency)
(7) Squelch (level 9)
(8) Squelch (level 3)
(9) CTCSS deviation (Wide)
(10) CTCSS deviation (Narrow)
(11) CDCSS deviation (Wide)
(12) CDCSS deviation (Narrow)
CH 13~16 are for adjusting transmitter and receiver. Press PTT to transmit; Press MONI
to choose Wide/Narrow, one Beep sound is Narrow, two Beep sound is Wide. CH 13~16
are defined as follows:
(13) Medium frequency (discrepancy between transmission and receive frequency is
0.1MHz).
(14) Lowest frequency (discrepancy between transmission and receive frequency is 0.1MHz).
(15) Highest frequency discrepancy between transmission and receive frequency is
-0.075MHz).
(16) Medium frequency: transmit with 250.3Hz CTCSS signals (discrepancy between
transmission and receive frequency is 0.1MHz).
Note :
To enable or disable manual adjusting mode: Short circuit the two SELF points, turn on the radio,
to enter the Mode Setting mode, and the manual adjusting function is enabled; press [PTT],
manual adjusting function is disabled. Once the manual adjusting function is disabled, the
manual adjusting mode can’t be accessed. This manual adjusting mode is suggested to be
disabled when adjustment finished.
III. CPU:
CPU control M38034M4
Pin No. Port
name I/O Function
1 TI I CTCSS/CDCSS Input
2 BUSY I Input busy signal
3 BATT I Detect battery voltage
4 NC I NC
5 TO O CTCSS/CDCSS Output
6 BEEP O Beep output
7 2TNI I 2-Tone input

TC-268/368 Service Manual
8
8 ENC0 I encode Input
9 ENC1 I encode Input
10 ENC2 I encode Input
11 ENC3 I encode Input
12 NC I NC
13 PTT I [PTT] input ,connect RXD
14 TXD O RS-232C output
15 RXD I RS-232C input
16 MONI I [MONI] input
17 SELF I Program L: mode setting
18 CNVSS I Connect VSS
19 RST I Reset input
20 INT0 I Power detection
21 NC I NC
22 XIN I Oscillator(7.3728MHz)
23 XOUT O Oscillator
24 VSS I Grounding
25 SHIFT O Clock frequency deviation H: unlock
26 PABC O MOSFETpower H:unlock
27 WNRC O Audio reference sensitivity L: narrow
28 WNTC O Maxdeviation H:narrow
29 NC I NC
30 SDA I/O EEPROM data cable
31 SCL O EEPROM clock cable
32 UL I PLL unlock detector L: unlock
33 DT O Common data output
34 CK O Common clock output
35 LE O PLLIC H:lockup
36 5MC O Power control except CPU and EEPROM L: unlock
37 AFCO O AF amplifier H: unlock
38 RX O TX/RXVCO H:receive
39 GLED O Green LED control H: light up
40 RLED O Red LED control H: light up
41 SAVE O Battery save control H: Battery save OFF
42 MUTE O Squelch control H: mic squelch L:AF squelch
43 5RC O Receiver power control L: unlock
44 5TC O Transmitter power control H: unlock
45 NC I NC
46 NC I NC
47 NC I NC
48 NC I NC
49 NC I NC
50 NC I NC
51 NC I NC
52 NC I NC
53 NC I NC
54 2TNO O 2-Tone output
55 VCCN O Frequency output
56 APC O TX: auto power control output RX:BPF tune output
57 VCC I CPU power 5V input
58 VREF I Connect with VCC
59 AVSS I Connect with VSS
60 NC I NC
61 NC I NC
62 NC I NC
63 NC I NC
64 TIBI I CTCSS/CDCSS external circuit central point input

TC-268/368 Service Manual
9
Circuit Description
1. Frequency configuration
The receiver utilizes double conversion superheterodyne. The first IF is 38.85MHz and the second IF
is 450kHZ. The first local oscillator signal is supplied from the PLL circuit.
The PLL circuit in the transmitter generates the necessary frequencies. Fig.1 shows the frequencies.
TC-268 frequency range: TC-268(1): 136MHz～150MHz
TC-268(2): 150MHz～174MHz
TC-368 frequency range: TC-368(1): 400MHz～420MHz
TC-368(2): 450MHz～470MHz
B
CC
B
ANT
ANTSW RF
MCF
38.85MHz
CF
450KHz
SYSTEM AF SP
X3
multiply
IF
TCXO 12.8MHz
MIC
AMP
MICPLL
VCO
RX
TX
TX
AMP
PA
AMP
AMP AMP
Fig. 1. Frequency configuration
2. Receiver
The receiver employs double conversion superheterodyne.
1-a) Front-end RF amplifier (TC-268)
An input signal from the antenna is applied to an RF amplifier (Q203) after passing through a
transmit/receive switch circuit (D 102 and D103 are off) and a band pass filter (L208, L209 and L210).
After the signal is amplified (Q203), the signal is filtered through a band pass filter (L203 and L214) to
eliminate unwanted signals before it is passed to the first mixer. Band pass filters (L208, L209, L210,
L203 and L214) have varactor diodes (D203, D204, D206, D202 and D201). The voltage of varactor is
provided by the MPU (IC403) center frequency of the band pass filter. (See Fig. 2-a)
B
CC
B
ANT
D102
D103 BPF Q203
RF AMP
L208-L210 BPF L214L215 MCF XF200 IF AMP Q201
MIXER
Q202
CF200
IF.MIX
IC200
AF AMP
LPF.HPF
IC300
AF PA AMP
IC302
SP
WIDE/NARROW SW
Q303
X3
multiply
Q1
TCXO
1st Local OSC
(PLL)
TUNE
APC
IC403
MCU
Fig. 2-a. Receiver configuration

TC-268/368 Service Manual
10
1-b) Front-end RF amplifier (TC-368)
An input signal from the antenna is applied to a RF amplifier (Q203) after passing through a
transmit/receive switch circuit (K102 and D103 are off) and a 3-pole LC filter. After the signal is
amplified (Q203), the signal is filtered by a band pass filter (a 3-pole LC filter) to eliminate unwanted
signals before it is passed to the first mixer. The voltage of varactor is provided by the MPU. (See Fig.
2-b)
B
CC
B
ANT
D102
D103 BPF Q203
RF AMP
L208-L211 BPF L214.L203.L204 MCF XF200 IF AMP Q201
MIXER
Q202
CF200
IF.MIX
IC200
AF AMP
LPF.HPF
IC300
AF PA AMP
IC302
SP
WIDE/NARROW SW
Q303
X3
multiply
Q1
TCXO
1st Local OSC
(PLL)
TUNE
APC
IC403
MCU
Fig. 2-b. Receiver configuration
2) First mixer
The signal from the RF amplifier is heterodyned with the first local oscillator signal from the PLL
frequency synthesizer circuit at the first mixer (Q202) to create a 38.85 MHz first intermediate frequency
(1st IF) signal. The first IF signal is then fed through two monolithic crystal filters (MCFs: XF200) to
further remove spurious signals.
3) IF amplifier
The first IF signal is amplified by Q201, and then enters IC 200 (IF processing IC). The signal is
heterodyned again with a second local oscillator signal within IC200 to create a 450kHz second IF
signal. The second IF signal is then fed through a 450kHz ceramic filter (CF200) to further eliminate
unwanted signals before it is amplified and FM detected in IC200.
4) AF amplifier
The recovered AF signal obtained from IC200 is amplified by IC300 (1/4), filtered by the IC300
low-pass filter (2/4) and IC300 high-pass filter (3/4) and (4/4), and de-emphasized by R303 and C306,
and then passed through a WIDE/NARROW switch (Q303). The processed AF signal passes through
an AF volume control and is amplified by an AF power amplifier (IC302) to a sufficient level to drive a
loud speaker.
5) Squelch
Part of the AF signal from the IC re-enters the FM IC, and the noise component is amplified and
rectified by a filter and an amplifier to produce a DC voltage corresponding to the noise level.
The DC signal from the FM IC goes to the analog port of the microprocessor (IC403). IC403 determines
whether to output sounds from the speaker, IC403 sends a high signal to the MUTE and AFCO lines and turns
IC302 on through Q302, Q304, Q305, Q306 and Q307. (See Fig.3)

TC-268/368 Service Manual
11
FM IF IC200
IF AMP DET
DET HPF
AMP
IC 300
AF AMP LPF HPF Q302 SW IC302 AF/PF AMP Q307 SW
SP
Q304.Q305.Q306
SW
Q303
W/N SW
IC301
LPF
562676
BUSY MUTE AFCO TI
IC403
MPU
Fig. 3. AF Amplifier and squelch
6) Receiving signaling
CTCSS/CDCSS
300 Hz and higher audio frequencies of the output signal from IF IC are cut by a low-pass filter
(IC301). The resulting signal enters the microprocessor (IC403). IC403 determines whether the CTCSS
or CDCSS matches the preset value, and controls the MUTE and AFCO and the speaker output sounds
according to the squelch results.
3. PLL frequency synthesizer
The PLL circuit generates the first local oscillator signal for reception and the RF signal for
transmission.
1)PLL
The frequency step of the PLL circuit is 5 or 6.25kHz. A 12.8MHz reference oscillator signal is divided
at IC1 by a fixed counter to produce the 5 or 6.25kHz reference frequency. The voltage controlled
oscillator (VCO) output signal is buffer amplified by Q6, then divided in IC1 by a dual-module
programmable counter. The divided signal is compared in phase with the 5 or 6.25kHz reference signal
in the phase comparator in IC1. The output signal from the phase comparator is filtered through a
low-pass filter and passed to the VCO to control the oscillator frequency. (See Fig. 4 of Next Page)
B
C
DD
C
B
PLL DATA
PLL IC IC1
I/N 5KHz/6.25KHz
PHASE
COMPARATOR
REF OSC
12.8MHz
I/M 5KHz/6.25KHz
CHARGE
LPF
D2.4 Q4 TX VCO
D1.3 Q3 RX VCO
Q6
BUFF AMP
Q5.7
T/R SW
Q2
RF AMP
PUMP
Fig. 4. PLL circuit

TC-268/368 Service Manual
12
2) VCO
The operating frequency is generated by Q4 in transmit mode and Q3 in receive mode. The oscillator
frequency is controlled by applying the VCO control voltage, obtained from the phase comparator, to the
varactor diodes (D2 and D4 in transmit mode and D1 and D3 in receive mode). The T/R pin is set high
in receive mode causing Q5 and Q7 to turn Q4 off, and turn Q3 on. The T/R pin is set low in transmit
mode. The outputs from Q3 and Q4 are amplified by Q6 and sent to the buffer amplifiers.
3) UNLOCK DETECTOR
If a pulse signal appears at the LD pin of IC1, an unlock condition occurs, and the DC voltage
obtained from D7, R6, and C1 causes the voltage applied to the UL pin of the microprocessor to go low.
When the microprocessor detects this condition, the transmitter is disabled, ignoring the push-to-talk
switch input signal. (See Fig. 5)
IC1
LD
PLL IC
D7
5C
R6
C1
IC403
UL
MPU
Fig. 5. Unlock detector circuit
4. Transmitter
1) Transmit audio
The modulation signal from the microphone is amplified by IC500 (1/2), passes through a
pre-emphasis circuit, and amplified by the other IC500 (1/2) to perform IDC operation. The signal then
passes through a low-pass filter (splatter filter) (Q501 and Q502) and cuts 3kHz and higher frequencies.
The resulting signal goes to the VCO through the VCO modulation terminal
for direct FM modulation. (See Fig. 6)
2) CTCSS/CDCSS encoder
A necessary signal for CTCSS/CDCSS encoding is generated by IC403 and FM-modulated to the
PLL reference signal. Since the reference OSC does not modulate the loop characteristic frequency or
higher, modulation is performed at the VCO side by adjusting the balance. (See Fig. 6)
VCO
D5.Q4
VR500
BALANCE
VR501
MAX
DEV
X1.IC1
PEFERENCE
OSC
CTCSS/CDCSS
TO
TTS
TTS
MUTE
Q503
SW
MIC
IC500(1/2)
MIC
AMP PREEMPHASIS IC500(1/2)
IDC
Q501.502
LPF
(SPATTER FILTER)
IC403
Fig. 6. Transmit audio CTCSS/CDCSS

TC-268/368 Service Manual
13
3-a) RF amplifier (TC-268)
The transmit signal obtained from the VCO buffer amplifier Q100, is amplified by Q101. This amplified
signal is passed to the power amplifier, Q102 and Q105, which consists of a 2-stage FET amplifier and
is capable of producing up to 5W of RF power (See Fig. 7-a)
D
C
B
A
Title
Number RevisionSize
AMP
Q101
5T
DRIVE AMP
Q102
FINAL AMP
Q105
ANT SW
D101 LPF
ANT
ANT SW
D102.103
RX
Q106
SW
Q109
SW
5T
IC100
APC
DET
Q103.Q104
B SW
B
APC
5T
TH100
SW
Q107
5T
Q108
SW
Fig. 7-a. APC system
3-b) RF amplifier (TC-368)
The transmit signal obtained from the VCO buffer amplifier Q100, is amplified by Q101 and Q102.
This amplified signal is passed to the power amplifier, Q105 and Q107, which consists of
a 2-stage FET amplifier and is capable of producing up to 4W of RF power (See Fig. 7-b)
D
C
B
A
Title
Number RevisionSize
AMP
Q101.102
5T
DRIVE AMP
Q105
FINAL AMP
Q107
ANT SW
D101 LPF
ANT
ANT SW
D102.103
RX
Q106
SW
Q109
SW
5T
IC100
APC
DET
Q103.Q104
B SW
B
APC
5T
TH102
SW
Q110
5T
Q108
SW
Fig. 7-b. APC system

TC-268/368 Service Manual
14
4) ANT switch and LPF
The RF amplifier output signal is passed through a low-pass filter network and a transmit/receive
switching circuit before it is passed to the antenna terminal. The transmit/receive switching circuit is
comprised of D101, D102 and D103. D102 and D103 turned on (conductive) in transmit mode and off
(isolated) in receive mode.
5) APC
The automatic power control (APC) circuit stabilizes the transmitter output power at a predetermined
level by sensing the drain current of the final amplifier Field Effect Transistor (FET). The voltage
obtained from the above drain current with a reference voltage which is set using the microprocessor.
An APC voltage proportional to the difference between the sensed voltage and the reference voltage
appears at the output of IC100 (1/2). This output voltage controls the gate of the FET power amplifier,
which keeps the transmitter output power can be varied by the microprocessor which in turn changes
the reference voltage and hence , the output power.
6) Terminal protection circuit
When the thermistor (TH102) reaches about 80 , the protection circuit turns on Q110 to protect℃
transmitting final amplifier (Q107).
5. Power supply
A 5V reference power supply [5M] for the control circuit is derived from an internal battery. This
reference is used to provide a 5V supply in transmit mode [5T], a 5V supply in receive mode [5R] , and
a 5V, supply common in both modes [5C] based on the control signal sent from the microprocessor.
6. Control system
The IC403 CPU operates at 7.37MHZ. This oscillator has a circuit that shifts the frequency according
to the EEPROM data.

TC-268/368 Service Manual
15
Parts List 1
No. Material No. Material Name Qty Ref No. Print No.
1 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R118 B3G
2 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R123 B4I
3 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R213 B5E
4 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R222 B4E
5 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R232 B5F
6 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R233 B4F
7 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R240 B4H
8 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R28 B1D
9 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R29 B2C
10 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R327 T2E
11 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R329 B2A
12 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R404 T2B
13 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R419 B2I
14 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R431 T4J
15 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R5 B1C
16 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R531 T2G
17 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R539 T5H
18 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R542 T3G
19 3001060000000 Chip resistor 0603 0ΩJ 1/10W 1 R7 B1C
20 3001061000000 Chip resistor 0603 10ΩJ 1/10 1 R109 B3G
21 3001061000000 Chip resistor 0603 10ΩJ 1/10 1 R200 B5C
22 3001061000000 Chip resistor 0603 10ΩJ 1/10 1 R3 B2D
23 3001061000000 Chip resistor 0603 10ΩJ 1/10 1 R334 T2F
24 3001061000000 Chip resistor 0603 10ΩJ 1/10 1 R412 T3B
25 3001061000000 Chip resistor 0603 10ΩJ 1/10 1 R417 T4K
26 3001061010000 Chip resistor 0603 100ΩJ 1/1 1 R104 B2G
27 3001061010000 Chip resistor 0603 100ΩJ 1/1 1 R14 B3D
28 3001061010000 Chip resistor 0603 100ΩJ 1/1 1 R223 B3E
29 3001061010000 Chip resistor 0603 100ΩJ 1/1 1 R430 T4J
30 3001061010000 Chip resistor 0603 100ΩJ 1/1 1 R530 T4H
31 3001061010000 Chip resistor 0603 100ΩJ 1/1 1 R537 T5I
32 3001061010000 Chip resistor 0603 100ΩJ 1/1 1 R538 T5H
33 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R103 B2F
34 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R2 B1C
35 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R20 B2D
36 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R225 B3E
37 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R229 B5E
38 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R27 B1F
39 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R328 B1A
40 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R4 B3D
41 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R405 T4B
42 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R407 T2A
43 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R409 T3B
44 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R413 T2D
45 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R420 B2I
46 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R427 B2H
TC-268 (1) Parts List 1

TC-268/368 Service Manual
16
Parts List 1
47 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R508 T3E
48 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R536 T5J
49 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R6 T5C
50 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R608 T1A
51 3001061020010 Chip resistor 0603 1KΩJ 1/10 1 R703 T4I
52 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R140 T2I
53 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R15 B1D
54 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R214 B3E
55 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R308 B3A
56 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R432 B2H
57 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R435 B2H
58 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R511 T3F
59 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R516 T3F
60 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R601 T2A
61 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R603 T2A
62 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R605 T2A
63 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R701 T4H
64 3001061030010 Chip resistor 0603 10KΩJ 1/1 1 R702 T4H
65 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R146 T1H
66 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R17 B2E
67 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R207 B5B
68 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R21 B2D
69 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R226 B4E
70 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R230 B5F
71 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R237 B4F
72 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R238 B4H
73 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R239 B4H
74 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R24 B1F
75 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R291 B4F
76 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R294 B4F
77 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R323 B4A
78 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R325 B4A
79 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R341 T1F
80 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R401 T4C
81 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R408 T2A
82 3001061040010 Chip resistor 0603 100KΩJ 1/ 1 R533 T4I
83 3001061050010 Chip resistor 0603 1MΩJ 1/10 1 R142 T2I
84 3001061050010 Chip resistor 0603 1MΩJ 1/10 1 R304 B3B
85 3001061230000 Chip resistor 0603 12KΩJ 1/1 1 R101 B2F
86 3001061230000 Chip resistor 0603 12KΩJ 1/1 1 R312 B2B
87 3001061240000 Chip resistor 0603 120KΩD 1/ 1 R23 B2F
88 3001061240000 Chip resistor 0603 120KΩD 1/ 1 R306 B3A
89 3001061240000 Chip resistor 0603 120KΩD 1/ 1 R340 B1B
90 3001061240000 Chip resistor 0603 120KΩD 1/ 1 R509 T2C
91 3001061510000 Chip resistor 0603 150ΩJ 1/1 1 R10 B1D
92 3001061510000 Chip resistor 0603 150ΩJ 1/1 1 R13 B1D
93 3001061510000 Chip resistor 0603 150ΩJ 1/1 1 R231 B5F
94 3001061510000 Chip resistor 0603 150ΩJ 1/1 1 R332 T2E
TC-268 (1) Parts List 1

TC-268/368 Service Manual
17
Parts List 1
95 3001061520000 Chip resistor 0603 1.5KΩJ 1/ 1 R108 B3F
96 3001061520000 Chip resistor 0603 1.5KΩJ 1/ 1 R525 T4G
97 3001061530000 Chip resistor 0603 15KΩD 1/1 1 R433 B2H
98 3001061530000 Chip resistor 0603 15KΩD 1/1 1 R434 B1H
99 3001061530000 Chip resistor 0603 15KΩD 1/1 1 R513 T2C
100 3001061530000 Chip resistor 0603 15KΩD 1/1 1 R526 T3G
101 3001061530000 Chip resistor 0603 15KΩD 1/1 1 R527 T3G
102 3001061530010 Chip resistor 0603 15KΩJ 1/1 1 R143 T1H
103 3001061540010 Chip resistor 0603 150KΩD 1/ 1 R1 B1C
104 3001061540010 Chip resistor 0603 150KΩD 1/ 1 R133 T1I
105 3001061540010 Chip resistor 0603 150KΩD 1/ 1 R134 T1I
106 3001061540010 Chip resistor 0603 150KΩD 1/ 1 R135 T1I
107 3001061540010 Chip resistor 0603 150KΩD 1/ 1 R136 T1I
108 3001061540010 Chip resistor 0603 150KΩD 1/ 1 R137 T1I
109 3001061540010 Chip resistor 0603 150KΩD 1/ 1 R138 T1I
110 3001061540010 Chip resistor 0603 150KΩD 1/ 1 R518 T2C
111 3001061800000 Chip resistor 0603 18ΩJ 1/10 1 R112 B3F
112 3001061810000 Chip resistor 0603 180ΩJ 1/1 1 R403 B2K
113 3001061820000 Chip resistor 0603 1.8KΩJ 1/ 1 R114 B3G
114 3001061820000 Chip resistor 0603 1.8KΩJ 1/ 1 R522 T3F
115 3001061820000 Chip resistor 0603 1.8KΩJ 1/ 1 R534 T5H
116 3001061830010 Chip resistor 0603 18KΩJ 1/1 1 R305 B2A
117 3001061830010 Chip resistor 0603 18KΩJ 1/1 1 R529 T4G
118 3001061840000 Chip resistor 0603 180KΩJ 1/ 1 R145 T1I
119 3001061840000 Chip resistor 0603 180KΩJ 1/ 1 R202 B4B
120 3001061840000 Chip resistor 0603 180KΩJ 1/ 1 R206 B4B
121 3001061840000 Chip resistor 0603 180KΩJ 1/ 1 R293 B4F
122 3001061840000 Chip resistor 0603 180KΩJ 1/ 1 R318 B4A
123 3001061850000 Chip resistor 0603 1.8MΩJ 1/ 1 R512 T3E
124 3001061850000 Chip resistor 0603 1.8MΩJ 1/ 1 R517 T3F
125 3001062210000 Chip resistor 0603 220ΩJ 1/1 1 R102 B2F
126 3001062210000 Chip resistor 0603 220ΩJ 1/1 1 R210 B5C
127 3001062210000 Chip resistor 0603 220ΩJ 1/1 1 R402 B2K
128 3001062220000 Chip resistor 0603 2.2KΩJ 1/ 1 R331 T1E
129 3001062220000 Chip resistor 0603 2.2KΩJ 1/ 1 R406 B2J
130 3001062220000 Chip resistor 0603 2.2KΩJ 1/ 1 R418 T2C
131 3001062230000 Chip resistor 0603 22KΩJ 1/1 1 R321 B1B
132 3001062230000 Chip resistor 0603 22KΩJ 1/1 1 R504 T2D
133 3001062240000 Chip resistor 0603 220KΩD 1/ 1 R322 B2A
134 3001062240000 Chip resistor 0603 220KΩD 1/ 1 R411 T2A
135 3001062710000 Chip resistor 0603 270ΩJ 1/1 1 R127 B4J
136 3001062710000 Chip resistor 0603 270ΩJ 1/1 1 R128 B4J
137 3001062710000 Chip resistor 0603 270ΩJ 1/1 1 R18 B1F
138 3001062710000 Chip resistor 0603 270ΩJ 1/1 1 R22 B1E
139 3001062720000 Chip resistor 0603 2.7KΩJ 1/ 1 R209 B5C
140 3001062720000 Chip resistor 0603 2.7KΩJ 1/ 1 R422 B2H
141 3001062720000 Chip resistor 0603 2.7KΩJ 1/ 1 R428 B2H
142 3001062740000 Chip resistor 0603 270KΩD 1/ 1 R316 B3A
TC-268 (1) Parts List 1

TC-268/368 Service Manual
18
Parts List 1
143 3001062740000 Chip resistor 0603 270KΩD 1/ 1 R317 B2B
144 3001063300000 Chip resistor 0603 33ΩJ 1/10 1 R212 B3E
145 3001063310010 Chip resistor 0603 330ΩJ 1/1 1 R110 B3F
146 3001063310010 Chip resistor 0603 330ΩJ 1/1 1 R144 T2H
147 3001063310010 Chip resistor 0603 330ΩJ 1/1 1 R147 B3F
148 3001063310010 Chip resistor 0603 330ΩJ 1/1 1 R148 B3G
149 3001063310010 Chip resistor 0603 330ΩJ 1/1 1 R30 B2B
150 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R100 B2F
151 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R105 B3F
152 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R106 B3F
153 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R120 B3G
154 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R125 T2H
155 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R203 B4B
156 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R204 B4B
157 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R303 B2B
158 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R424 B2I
159 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R425 B2I
160 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R510 T3E
161 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R521 T3F
162 3001063320000 Chip resistor 0603 3.3KΩJ 1/ 1 R548 T2D
163 3001063330010 Chip resistor 0603 33KΩJ 1/1 1 R336 T2F
164 3001063330010 Chip resistor 0603 33KΩJ 1/1 1 R514 T3E
165 3001063330010 Chip resistor 0603 33KΩJ 1/1 1 R515 T3F
166 3001063330010 Chip resistor 0603 33KΩJ 1/1 1 R519 T3F
167 3001063330010 Chip resistor 0603 33KΩJ 1/1 1 R520 T3F
168 3001063340000 Chip resistor 0603 330KΩJ 1/ 1 R400 T2B
169 3001063340000 Chip resistor 0603 330KΩJ 1/ 1 R8 B3D
170 3001063920000 Chip resistor 0603 3.9KΩJ 1/ 1 R107 B3F
171 3001063920000 Chip resistor 0603 3.9KΩJ 1/ 1 R201 B3B
172 3001063920000 Chip resistor 0603 3.9KΩJ 1/ 1 R220 B3E
173 3001063930010 Chip resistor 0603 39KΩJ 1/1 1 R12 B3B
174 3001063930010 Chip resistor 0603 39KΩJ 1/1 1 R607 T2B
175 3001063940000 Chip resistor 0603 390KΩD 1/ 1 R315 B1A
176 3001064700000 Chip resistor 0603 47ΩJ 1/10 1 R116 B3G
177 3001064700000 Chip resistor 0603 47ΩJ 1/10 1 R117 B3H
178 3001064700000 Chip resistor 0603 47ΩJ 1/10 1 R215 B3E
179 3001064700000 Chip resistor 0603 47ΩJ 1/10 1 R228 B5E
180 3001064710000 Chip resistor 0603 470ΩJ 1/1 1 R211 B3E
181 3001064710000 Chip resistor 0603 470ΩJ 1/1 1 R535 T5H
182 3001064720000 Chip resistor 0603 4.7KΩJ 1/ 1 R119 T2J
183 3001064720000 Chip resistor 0603 4.7KΩJ 1/ 1 R26 B2G
184 3001064720000 Chip resistor 0603 4.7KΩJ 1/ 1 R416 T4C
185 3001064720000 Chip resistor 0603 4.7KΩJ 1/ 1 R500 T2C
186 3001064720000 Chip resistor 0603 4.7KΩJ 1/ 1 R501 T2C
187 3001064720000 Chip resistor 0603 4.7KΩJ 1/ 1 R507 T4C
188 3001064720000 Chip resistor 0603 4.7KΩJ 1/ 1 R541 T5C
189 3001064730000 Chip resistor 0603 47KΩJ 1/1 1 R11 B3B
190 3001064730000 Chip resistor 0603 47KΩJ 1/1 1 R115 B3G
TC-268 (1) Parts List 1