HYT TC-265, TC-365 Service Manual

TC-265/365 SERVICE MANUAL

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Contents

Revision History…………………………………………………………………………………1
General……………………………………………………………………………………………3
Radio Overview..………………………………………………………………………………3
Radio Modes……………………………………………………………………………………5
Circuit Description……………………………………………………………………………13
CPU Pins…………………………………………………………………………………………19
TC-265 Parts List 1……………………………………………………………………………21
TC-365 Parts List 1……………………………………………………………………………36
Adjustment Description………………………………………………………………………55
Disassembly for Repair………………………………………………………………………58
Exploded View…………………………………………………………………………………59
TC-265/365 Parts List 2………………………………………………………………………60
Packing…………………………………………………………………………………………62
TC-265 PC Board View………………………………………………………………………63
TC-365 PC Board View………………………………………………………………………65
TC-265 Schematic Diagram…………………………………………………………………67
TC-365 Schematic Diagram…………………………………………………………………68
Specifications…………………………………………………………………………………69

TC-265/365 SERVICE MANUAL

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Revision History

P/N Date Revision

2004.6

8130026500010 2006.10 IC302 is changed from TA7368F to KIA6278F; Q203/Q203 is changed from

3SK320 to 3SK318; Q102 is changed from 2SK2596 to RD01; Q105 is
changed from 2SK2595 to RD07. Changes also be made on the corresponding
peripheral circuits.

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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.

Safety and General Information

The following general safety precautions as would normally apply, should be observed during all phases
of operation, service and repair of this equipment.

z This equipment should be serviced by qualified technicians only.

z DO NOT operate the transmitter of radio unless all RF connectors are secure and any open

connectors are properly terminated.

z Do not modify the radio for any reason.

z Use only HYT original batteries and chargers.

z Use only the supplied or an approved antenna.

z Do not use any portable radio that has a damaged antenna. If a damaged antenna comes into

contact with your skin, a minor burn can result.

z 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. Air bags inflate with great force. If a radio is placed in the air bag deployment
area and the air bag inflates, the radio may be propelled with great force and cause serious injury to
occupants of the vehicle.

z Turn off your radio prior to entering any area with a potentially explosive atmosphere.

z Do not charge your battery in a potentially explosive atmosphere.

z To avoid possible interference with blasting operations, turn off your radio when you are near

electrical blasting caps, in a blasting area, or in areas posted: “Turn off two-way radio.” Obey all
signs and instructions.

z Do not expose the radio to direct sunlight over a long time, nor place it close to heating source.

z When using your radio, hold the radio in a vertical position with the microphone 3 to 4 centimeters

away from your lips.

z If you wear a radio on your body when transmitting, ensure that the radio and its antenna are at

least 2.5cm away from your body.

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Radio Overview

1. Mode

User mode: Turn on the radio to enter the mode.
PC mode：Set and adjust radio data with PC software or programmer in this mode.

2. Parts description:
(1) Antenna
(2) Channel Selector Knob

Turn the selector knob to select channels 1-S (channel S can be programmed by dealer as scan
function).

(3) LED Indicator

Used to indicate operation status of the radio. Different LED status indicates different operation status of
the radio. (See the following table).

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LED Indicates:
Red LED glows Transmitting
Red LED flashes Low battery
Green LED glows Monitoring or receiving
Orange LED glows Transmitting 2-Tone/5-Tone signaling
Orange LED flashes 2-Tone/5-Tone standby

(4) Radio On-Off/Volume Control Knob

Rotate the knob clockwise to turn the radio on, rotate the knob fully counter-clockwise until a “click” is
heard to turn the radio off.
Turn the knob clockwise to increase the volume, or counter-clockwise to decrease the volume.

(5) Speaker
(6) Microphone
(7) PTT (push to talk)

Press and hold PTT to talk, release to receive.

(8) Monitor Key

Press MONI key to monitor activities on the current channel.

(9) Speaker/Microphone Jack
(10) Belt Clip
(11) Battery
(12) Battery Latch

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Radio Modes

1. Frame of Radio Modes

Select the function from the modes and make settings according to your needs.

2. Description of Mode Functions

Mode Function

Conventional Mode This mode is used for normal operation.
PC Mode This mode is used to read/write parameters from/to

the radio and to make settings via PC.

Dealer Mode This mode is used for the dealer to set the

following modes: All Reset Mode; Manual Adjust
Mode; Wired Clone Mode.

All Reset Mode This mode is used to initialize the radio function

settings, channel data and destination and to
enable/disable manual adjust mode.

Manual Adjust Mode

This mode is used for the factory or dealer to make
the following adjustment: frequency stability, RX
sensitivity, squelch level, transmit power,
CTCSS/CDCSS deviation, tone deviation and low
battery alert reference value.

Wired Clone Mode This mode is used to transfer data from one radio

to another by an interface cable.

Test Mode Spare

User Mode Conventional Mode

PC Mode

Dealer Mode

All Reset Mode

Manual Adjust Mode

Wired Clone Mode

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3. Keyboard Entry for Mode Startup

Mode Key Remarks

Conventional
Mode

Power on

Turn the radio on to enter
conventional mode.

User Mode

PC Mode

Connect the radio with PC
through interface cable.

You can program the radio via
PC in user mode.
Short out the two SELF points
while turning the radio on.
Manual adjust mode is enabled.
Press [PTT] and [MONI]
simultaneously to reset.

All Reset Mode

Turn the radio on while shorting
out the two SELF points.

Press [PTT] for 3 seconds to
disable manual adjust mode.
In this mode, you can operate in
menu mode. In main menu,
press [PTT] to enter submenu.

Manual Adjust
Mode

Press [PTT] for 3 seconds while
turning the radio on. The radio
enters manual adjust mode if this
mode is enabled and enters user
mode if manual adjust mode is
prohibited.

In submenus, press [PTT]/[MONI]

to adjust upwards/downwards.
Hold down [MONI] and then
press [PTT] in 2 seconds to save
the value and return to the upper
menu.

Dealer Mode

Wired Clone
Mode

Press [MONI] for 3 seconds
while turning the radio on.

Press [PTT] to transmit.

4. Prohibit Entering Manual Adjust Mode

Manual adjust mode can be prohibited by programming to prevent users from changing the parameter
with self-programming function or with external programmer. The factory or the dealer should prohibit
this mode after setting and cancel the prohibition before entering this mode.

5. Operation in Radio Modes

In the following modes, when the two SELF points are shorted out, the radio enters all reset mode; if the
two points are disconnected, the radio enters other modes.

5.1 All Reset Mode

In this mode, you can initialize the radio parameters or enable/disable manual adjust mode.
Operation:
Short out the two SELF points, the radio enters all reset mode and manual adjust mode is enabled at the
same time. Use channel selector to select radio destination number (Please refer to the initial data table
for destination number of each model).

1. Press [PTT] and [MONI] simultaneously, the radio data are all reset.

2. Press [PTT] for 2 seconds, the manual adjust mode is prohibited.

3. Turn the radio off to exit from all reset mode and then enter other modes.

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5.2 Manual Adjust Mode

In this mode, the factory or the dealer can adjust the radio parameters in menu mode.
Operation:
Turn the radio on while holding down the [PTT], three beeps sound after 2 seconds and green LED
flashes. Release [PTT], a beep sounds and orange LED glows indicating that the radio enters manual
adjust mode.

1. In the main menu, turn channel selector to select adjustment items. Press [PTT] to enter the
submenu.

2. In the submenu, use channel selector to select among center, low, and high frequency or
narrowband/wideband. Press [PTT] to transmit or adjust upwards and press [MONI] to adjust
downwards.

3. After complete a setting, hold down [MONI] and then press [PTT] in 2 seconds, a beep sounds and
orange LED glows. The setting values are saved and the radio returns to the previous menu. Press
[PTT]/[MONI] more than 2 seconds to adjust setting values upwards/downwards. Turn the radio off
to cancel the setting.

4. CH1-CH9 are defined as follows:

Note: Frequency stability and VCO lock voltage should be adjusted before your adjustment to ensure

the reliability of the adjustment.

(1) Frequency stability and VCO lock voltage:
Adjust at center frequency CH1. Press [PTT] to switch between transmit and receive. Adjust frequency
stability at VR1, receive VCO at TC2 and transmit VCO at TC1. Turn to low frequency (CH2) and high
frequency (CH3) to check that the item is within the set range.

(2) RF BPF:
Adjust at center, low and high frequency. Adjust RF BPF at TC-201, TC-202 and TC-203. Pressing
[PTT]/[MONI] can adjust upwards/downwards. Receiver sensitivity can be tested in this mode.

(3) Squelch level 9:
Adjust at center, low and high frequency. Pressing [PTT]/[MONI] can adjust upwards/downwards.

(4) Squelch level 3:
Adjust at center, low and high frequency. Pressing [PTT]/[MONI] can adjust upwards/downwards.

(5) Transmit power:
Adjust at center, low and high frequency. Pressing [PTT]/[MONI] can adjust upwards/downwards.

(6) CTCSS deviation:
Adjust at center, low and high frequency. Adjust wideband at group 0 and narrowband at group 2.
CTCSS signal is 67.0Hz. Save the value. (Adjust wideband at group 1 and narrowband at group 3.
CTCSS signal is 250.3Hz. Adjust CTCSS balance at VR500.)
Pressing [PTT]/[MONI] can adjust upwards/downwards. Adjust balance of CTCSS deviation at center,
low, and high frequency.

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(7) CDCSS deviation:
Adjust at center, low and high frequency. Adjust wideband at group 0 and narrowband at group 2.
CDCSS is +023. Save the value. (Adjust wideband at group 1 and narrowband at group 3. CDCSS is
+754. Adjust CDCSS balance at VR500.) Pressing [PTT]/[MONI] can adjust upwards/downwards. Adjust
balance of CDCSS deviation at center, low, and high frequency.

(8) 2-Tone/5-Tone deviation:
Turn to any channel. Pressing [PTT]/[MONI] can adjust upwards/downwards. Tone signaling is 1860Hz.

(9) Low battery alert:
Turn to any channel. Adjust under maximum transmit power. Adjust power supply voltage to 80% of the
rate voltage: 5.8V. Press [PTT]/[MONI] so that red LED flashes.

Note:

1. TC-265/365 radio has 16 channels. Every four adjacent channels is a group. There are four groups
and they are marked as group 0, group 1, group 2 and group 3 respectively. The channel frequency
of each group is arranged as center, low, high and center frequency. Channels of group 0 and group
1 are wideband and channels of group 2 and group 3 are narrowband. You can adjust low frequency
of CTCSS/CDCSS (CTCSS: 67.0Hz, CDCSS: +023) at group 0 and group 2 and high frequency of
CTCSS/CDCSS balance (CTCSS: 250.3Hz, CDCSS: +754) at group 1 and group 3.

2. If the radio destination is not included in the initial data table, you can select VHF or UHF according
to the frequency range and IF and initialize the radio data through PC programming software.

5.3 PC Mode

You can make the following settings via PC. (Refer to the following table for more details.)
Machine serial number parameter;
General parameter;
User channel data;
Factory channel data (only for factory adjustment);
Center, low and high frequency (only for factory adjustment);
2-Tone frequency;
5-Tone frequency;
Initial data (only for factory adjustment);
Maintenance record.

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Function Setting:

Function

No.

Function

Name

Setting (Defaults are

underlined)

Display Remarks

OFF 1 OFF Disable
Monitor Momentary 1 1 AF channel opens when [MONI] is

held down.

Monitor Lock 1 2 Squelch opens when [MONI] is held

down. Switches each time [MONI] is
held down.

1 Monitor

SQ OFF Momentary 1 3 Squelch opens when [MONI] is held

down and compatible signal is

received.
OFF 2 OFF Disable
CO 2 CO Carrier operated scan (resume)

2 Channel

Scan

TO 2 TO Time operated scan (resume)
OFF 3 OFF No priority setting 3 Priority
ON 3 1 Set priority channel

4 1 4 Priority

Channel

0, 1-16
0

4 16

Priority (Only valid when ”fixed

priority ” is enabled)

5 0.5 5 Look

Back A

0.5-5.0s

1.0s
(step: 0.1s)

5 5.0

The period that radio checks a priority

channel from a normal channel when

there is no activity on priority channel.

6 0.5 6 RX Dwell

Time

0.5-5.0s

3.0s
(step: 0.1s)

6 5.0

Time until scan resumes when it is

stopped by signal input (Only valid in

time-operated scan).

7 0.1 7 Dropout
Delay
Time

0.1-5.0s

3.0s
(step: 0.1s)

7 5.0

Time until scan resumes when there is
no signal after it is stopped by signal
input.

8 0.1 8 TX Dwell
Time

0.1-5.0s

3.0s
(step: 0.1s)

8 5.0

Time until scan resumes after transmit
stops without compatible channel
associated signaling; Scan resume
time is decided by dropout delay
time/RX dwell time and
carrier-operated/time-operated scan
mode if compatible channel

associated signaling appears.
Current 9 0 It’s the current channel during scan. 9 Talk Back
Start + Last Stopped

9 1 It’s the channel where scan resumes

during scan; it’s the channel where

scan is stopped during scan.

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Priority +
Last Stopped

9 2 It’s priority channel during scan; It’s the

channel where scan is stopped during scan.
Assignment +
Last Stopped

9 3 It’s the assignment channel during scan; It’s

the channel where scan is stopped during

scan.
Last call 9 4 It’s the latest channel at pause during scan;

It’s the channel where scan is stopped during

scan; It’s the channel where scan starts if

scan never stops.
Last used 9 5 It’s the latest transmit channel during scan; It’s

the channel where scan is stopped during

scan; It’s the channel scan starts if scan never

stops.

10 OFF

10 1

10 Assignme

nt
Channel

0 OFF
1-16 ON
0

10 16

You can select any channel as revert channel

or talk back channel.

11 0 11 Squelch

Level

0-9 5
(step: 1)

11 9

Squelch level is set higher as the figure

increases.

12 OFF

12 30

12 Time Out

Timer

OFF 30-600s

60

(step:10s)

12 600

The maximum time of continuous

transmission. When OFF, in order to protect

power amplifier, time of continuous

transmission is set as 10 minutes.

13 OFF TOT off.

13 10

13

TOT Alert

Time

OFF 10-180s
OFF
(step:5s)

13 180

The radio will call an alert at the set time

before TOT is time out and then call alerts

every 10 seconds.

14 OFF Transmission is allowed immediately after the

radio returns to receive mode by TOT.

14 1

14 TOT

Rekey
Time

OFF 1-120s
OFF

(step:1s)

14 120

Transmission is prohibited until preset time

elapses.

15 OFF TOT is immediately reset after transmission

stops.

15 1

15 TOT

Reset
Time

OFF 1-60s
OFF
(step:1s)

15 60

TOT won’t reset until preset time elapses,

even if transmission has stopped.

Low 16 Low Low transmit power is selected. 16 Select

transmit
power

High

16 High High transmit power is selected.

Disable 17 OFF No battery save function 17 Battery

Save

Enable

17 ON Enable battery save function
OFF 18 OFF No beep tone 18 Beep
ON

18 ON Beep tone sounds

Disable 19 OFF Prohibit data clone. 19 Data

Clone
Enable

Enable

19 ON Permit data clone.

Disable 20 OFF Prohibit manual adjust mode. 20 Manual

Adjust
Mode

Enable

20 ON Permit manual adjust mode.

21 End 21 End

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5.4 PC Adjust Mode

The following parameters can be adjusted through PC (only for factory adjustment):
Adjustment data;
Maintenance record.

5.5 Wired Clone Mode

Turn the radio on while holding down the [MONI], after two seconds, a beep sounds and red LED flashes
indicating that the radio enters wired clone mode.
Operation:
(1) Press [PTT] to begin cloning and red LED flashes.
(2) Short out the clone mode points FCPY on PCB to enter factory clone mode.
(3) Disconnect the clone mode points FCPY on PCB to enter dealer clone mode.
(4) You can clone the following data in wired clone mode:
General parameter;
User channel data;
Factory channel data; (only available in factory clone mode)
Center, low and high frequency; (only available in factory clone mode)
2-Tone frequency;
5-Tone frequency;
Adjustment data; (only available in factory clone mode)

5.6 User Mode

Turn the radio on, a beep sounds and green LED flashes indicating that the radio enters user mode. This
mode is used for normal operation.

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6. Appendix: Initial data table

1CH (C) 2CH (L) 3CH (H) 4CH (C) No. Model Frequency

Range (MHz)

Center
Frequency (MHz)

IF (MHz)

Rx (MHz) Tx (MHz) Rx (MHz) Tx (MHz) Rx (MHz) Tx (MHz) Rx (MHz) Tx (MHz)

1 TC-265 (1)

136.000-150.000 143.000 +38.85 143.100 143.000 136.100 136.000 149.975 149.900 143.100 143.000

2 TC-265 (2)

136.000-174.000 155.000 +38.85 155.100 155.000 136.100 136.000 173.975 173.900 155.100 155.000

3 TC-265 (3)

146.000-174.000 160.000 +38.85 160.100 160.000 146.100 146.000 173.975 173.900 160.100 160.000

4 TC-265 (4)

150.000-174.000 162.000 +38.85 162.100 162.000 150.100 150.000 173.975 173.900 162.100 162.000

5 TC-265 (5)

155.000-164.000 160.000 +38.85 160.100 160.000 155.100 155.000 163.975 163.900 160.100 160.000

6 TC-265 (6)

216.000-223.000 219.000 +38.85 219.100 219.000 216.100 216.000 222.975 222.900 219.100 219.000

7 TC-365 (1)

330.000-350.000 340.000 -38.85 340.100 340.000 330.100 330.000 349.975 349.900 340.100 340.000

8 TC-365 (2)

350.000-370.000 360.000 -38.85 360.100 360.000 350.100 350.000 369.975 369.900 360.100 360.000

9 TC-365 (3)

370.000-390.000 380.000 -38.85 380.100 380.000 370.100 370.000 389.975 389.900 380.100 380.000

10 TC-365 (4)

400.000-420.000 410.000 -38.85 410.100 410.000 400.100 400.000 419.975 419.900 410.100 410.000

11 TC-365 (5)

400.000-430.000 415.000 -38.85 415.100 415.000 400.100 400.000 429.975 429.900 415.100 415.000

12 TC-365 (6)

420.000-450.000 435.000 -38.85 435.100 435.000 420.100 420.000 449.975 449.900 435.100 435.000

13 TC-365 (7)

440.000-470.000 455.000 -38.85 455.100 455.000 440.100 440.000 469.975 469.900 455.100 455.000

14 TC-365 (8)

450.000-470.000 460.000 -38.85 460.100 460.000 450.100 450.000 469.975 469.900 460.100 460.000

15 TC-365 (9)

470.000-490.000 480.000 -38.85 480.100 480.000 470.100 470.000 489.975 489.900 480.100 480.000

16 TC-365 (10)

480.000-520.000 500.000 -38.85 500.100 500.000 480.100 480.000 519.975 519.900 500.100 500.000

17 Factory

adjustment
(VHF)

100.000-500.000 300.000 +38.85 300.100 300.000 100.100 100.000 499.975 499.900 300.100 300.000

18 Factory

adjustment
(UHF)

200.000-600.000 400.000 -38.85 400.100 400.000 200.100 200.000 599.975 599.900 400.100 400.000

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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 by PLL circuit.

The PLL circuit in the transmitter generates the necessary frequencies. Fig.1 shows the circuit
configuration.

TC-265 frequency range: 146MHz—174MHz
TC-365 frequency range: 440MHz—470MHz

ANT SW

ANT

RF AMP

MIXER

CF

MCF

AF AMP
LPF.HPF

SP

TCXO multiply

IF.MIX

TX AMP

PA AMP AMP

MIC

MIC

PLL

VCO

12.8M

Fig. 1. Circuit configuration

2. Receiver

The receiver employs double conversion superheterodyne.

1-a) Front end RF amplifier (TC-265)

The input signal of antenna is applied to an RF amplifier (Q203) after passing through a
transmit/receive switch circuit and a 3-stage low pass filter. The amplified signal is filtered through a
band pass filter (a 3-stage LC filter) to eliminate unwanted signal before it is applied to the first mixer.
The voltage of varactor is provided by MPU (IC403). (See Fig. 2-a)

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ANT

ANT SW RF AMPBPF MCF IF AMPMIXER

CF200

IF.MIX

AF AMP
LPF.HPF

AF PA AMP

SP

multiplyTCXO

1st Local OSC

(PLL)

BPF

MCU

X3

APC

TUNE

Fig. 2-a. Receiver configuration

1-b) Front end RF amplifier (TC-365)

The input signal of antenna is applied to an RF amplifier (Q122) after passing through a
transmit/receive switch circuit and a 3-stage low pass filter. The amplified signal is filtered through a
band pass filter (a 3-stage LC filter) to eliminate unwanted signal before it is applied to the first mixer.
The voltage of varactor is provided by MPU (IC3). (See Fig. 2-b)

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ANT SW

MCU

APC

ANT

BPF BPF

RF AMP

MIXER

IF AMP

CF100

MCF

AF AMP
LPF.HPF

AF PA AMP

SP

TUNE

1st Local OSC

(PLL)

TCXO

X5

multiply

IF.MIX

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 to create a 38.85 MHz first IF (intermediate frequency)
signal. The first IF signal is then applied to two monolithic crystal filters to further remove spurious
signal.

3) IF amplifier

The first IF signal is amplified by Q201（TC-265）/Q124（TC-365）, and then enters IF processing IC.

The signal is heterodyned again with a second local oscillator signal within IF processing IC to create
a 450KHz second IF signal. The second IF signal is then fed through a 450KHz ceramic filter to
further eliminate unwanted signals before it is amplified and FM detected in IC200（TC-265）/IC10

（TC-365）.

4) AF amplifier

The recovered AF signal obtained from IF processing IC is amplified by IC300 (1/4)（TC-265）/IC9

（1/4）（TC-365）, filtered by the IC300（TC-265）/IC9（TC-365） low-pass filter (2/4) and IC300

（TC-265）/IC9（TC-365） high-pass filter (4/4), and de-emphasized by R47 and C56（TC-265）/ R36

and C53（TC-365）. The processed AF signal is then passed to a WIDE/NARROW switch and its

output is applied to an AF volume control circuit and is amplified to a sufficient level to drive a loud
speaker by an AF power amplifier .

5) Squelch

Part of the AF signal from IF processing IC re-enters 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 is injected to the analog port of the microprocessor. MCU compares the voltage with
the preset value and determines whether to output sounds from the speaker. MCU sends a high level
signal to the MUTE and AFCO lines and turns IC302(TC-265)/IC7(TC-365) on through Q302, Q304,
Q305, Q306 and Q307（TC-265）/Q115, Q116, Q117, Q118（TC-365）

. (See Fig.3)

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FM IF IC

IF AMP DET

DET

HPF AMP

AF

AF AMP HPF MUTE SW AF PF AMP AFCO SW

SP

AFCO SW

LPF

137422

BUSY

MUTE

AFCO

TI

MPU

QT/DQT

LPF

W/N SW

Fig. 3. AF amplifier and squelch

6) Receiving signaling

CTCSS/CDCSS
MCU output signal is filtered by 300Hz low-pass filter and the filtered signal is input to the
microprocessor. MCU determines whether the CTCSS or CDCSS matches the preset value, and
controls the MUTE and AFCO and the speaker sounds output according to the squelch results.
2-Tone/5-Tone
IF processing IC output signal is filtered by IC9（TC-265）/IC14（TC-365）and then applied to the

microprocessor. MCU compares TTS with the preset value and controls MUTE and AFCO and
speaker output according to squelch results.

3. PLL frequency synthesizer

PLL circuit generates the first local oscillator signal for receive and the RF signal for transmission.

1) PLL

The frequency step of the PLL circuit is 2.5 or 6.25 KHz. A 12.8MHz reference oscillator signal is
divided at PLL by a mixed counter to produce 2.5 or 6.25 KHz reference frequency. The voltage
controlled oscillator (VCO) output signal is buffer amplified, and then divided in PLL by a dual-module
programmable counter. The divided signal is compared in phase with the 2.5 or 6.25 KHz reference
signal in the phase comparator in PLL. 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)

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PLL DATA

PLL IC

I/N

5KHz/6.25KHz

PHASE

COMPARATOR

REF OSC

12.8MHz

I/M

5KHz/6.25KHz

CHARGE

LPF

TX VCO

RX VCO

BUFF AMP

VCO
T/R SW

RF AMP

PUMP

Fig. 4. PLL circuit

2) VCO

The operating frequency is generated by Q4(TC-265）/Q141（TC-365）in transmit mode and Q3

（TC-265）/Q142（TC-365）in receive mode. The oscillator frequency is controlled through applying

the VCO control voltage, which is obtained from the phase comparator to the varactor diodes. The T/R
pin is set high in receive mode causing Q5 and Q7 to turn Q4 off, and turn Q3 on（TC-265）/Q140 and

Q138 to turn Q141 off, and turn Q142 on(TC-365). The T/R pin is set low in transmit mode. The
outputs are amplified by Q6（TC-265）/Q139（TC-365） and sent to the buffer amplifiers.

3) Unlock Detector

If a low level signal appears at the LD pin of PLL IC, an unlock condition occurs, and the DC voltage
obtained from D7, R2（TC-265）/D114，R501（TC-365）, and PLL IC 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)

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5C

LD UL

Fig. 5. Unlock detector circuit

4. Transmitter

1) Transmit audio

The modulation signal from the microphone is amplified by IC500（TC-265）/IC1(TC-365) (1/2), and

then passes through a pre-emphasis circuit and a 3KHz low-pass filter. The resulting signal goes to
the VCO for direct FM modulation. (See Fig. 6)

TC-265/365 SERVICE MANUAL

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2) CTCSS/CDCSS encoder

A necessary signal for CTCSS/CDCSS encoding is generated by MCU and FM-modulated to the PLL
IC 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)

3) 2-Tone/5-Tone encoder

The necessary signal for 2-Tone/5-Tone encoding is generated by MCU. The signal is sent to
IC500(TC-265）/IC1（TC-365）(2/2), and then applied to 3KHz low-pass filter. The resulting signal is

applied to VCO for direct modulation (See fig. 6).

MCU

MUTE

PRE EMPHASIS

LPF

IDC

MAX DEV

VCO

(TCXO)

OSC

REFERENCE

MIC

MIC AMP

TO

2 TN/5 TN

Decoder

Balance

MUTE SW

Fig. 6. Transmit audio CTCSS/CDCSS

4-a) RF amplifier (TC-265)

The RF signal obtained from the VCO buffer amplifier Q100 is amplified by Q101 and Q102. 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 4.5W of RF power (See Fig. 7-a).

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SW

ANT SW

LPF

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B SW

APC

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B

APC

5T

5T

SW

Fig. 7-a. APC system

4-b) RF amplifier (TC-365)

The RF signal obtained from the VCO buffer amplifier Q136 is amplified by Q135 and Q134. This
amplified signal is passed to the power amplifier, Q131 and Q129, which consists of a 2-stage FET
amplifier and is capable of producing up to 4W of RF power (See Fig. 7-b)

TC-265/365 SERVICE MANUAL

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APC

5T

5T

SW

Fig. 7-b. APC system

5) ANT switch and LPF

The RF amplifier output signal is passed through a low-pass filter network to filter the second
harmonic components and then applied to a transmit/receive switching circuit before it is passed to
the antenna terminal. The transmit/receive switching circuit is comprised of D100, D200 and D101.
D102 and D103（TC-265）/ D108, D112 and D111. D109 and D110（TC-365） is turned on (conductive)

in transmit mode and off (isolated) in receive mode.

6) 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
comparison circuit compares the voltage obtained from the above drain current with a reference
voltage which is set using the microprocessor. The APC voltage is proportional to the difference

between the sensed voltage and the reference voltage output from IC100 （TC-265）/IC11（TC-365）

(1/2). This output voltage controls the gate of the FET power amplifier, which keeps the transmitter
output power be varied by the microprocessor which in turn changes the reference voltage and hence,
the output power.

7) Temperature protection circuit

When the thermistor TH100（TC-265）/TH102（TC-365） reaches about 80℃, the protection circuit
turns on Q107（TC-265）/Q126(TC-365) to protect the final-stage amplifier from overheating.

5. Power supply

A 5V reference power supply [5M] for the control circuit is derived from an internal battery. This reference
power supply 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 MCU operates at 7.37MHz. This oscillator has a circuit that shifts the frequency according to the
EEPROM data.

TC-265/365 SERVICE MANUAL

－ 19 －

CPU Pins

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 Output CTCSS/CDCSS

6 BEEP O Beep output

7 NC I NC
8 ENC0 I Input encode

9 ENC1 I Input encode
10 ENC2 I Input encode
11 ENC3 I Input encode
12 TSI I AF signaling decode input
13 PTT I [PTT] input, connect with RXD
14 TXD O RS-232C output
15 RXD I RS-232C input
16 MONI I [MONI] input
17 SELF I Self-Program L: set up model
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 shift H: enable
26 PABC O MOS FET power H: enable
27 WNRC O Audio reference sensitivity L: narrow
28 WNTC O Max deviation control 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 PLL IC H: lock up
36 5MC O Power control except for CPU and EEPROM L: unlock
37 AFCO O AF amplifier H: unlock
38 RX O TX/RX VCO H: receive
39 GLED O Green LED control H: light
40 RLED O Red LED control H: light
41 SAVE O Battery save control H: battery save OFF
42 MUTE O mute 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

TC-265/365 SERVICE MANUAL

－ 20 －

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 NC I NC
55 TSO O AF signaling encode output
56 APC O TX: APC output RX: BPF tune output
57 VCC I CPU power supply 5V
58 VREF I Connect with VCC
59 AVSS I Connect with VSS
60 NC I NC
61 FCPY I Factory clone L: model set
62 MODE I Additional mode L: enable
63 NC I NC
64 TIBI I CTCSS/CDCSS exterior circuit central input