HYT TC-780 Bedienungsanleitung

Contents

General.....................................................................................................................................................1

Radio Overview ........................................................................................................................................2

Software Specifications ............................................................................................................................5

Circuit Description ....................................................................................................................................6

CPU Pins................................................................................................................................................13

TC-780 VHF Parts List 1 (Main Board Unit) ...........................................................................................18

TC-780 UHF Parts List 1 (Main Board Unit) ...........................................................................................18

TC-780 VHF/UHF Parts List 1 (Keyboard Unit) ......................................................................................18

Adjustment Description...........................................................................................................................18

Troubleshooting Flow Chart ...................................................................................................................27

Disassembly and Assembly for Repair ...................................................................................................32

Exploded View........................................................................................................................................36

TC-780 Parts List 2.................................................................................................................................37

Packing...................................................................................................................................................39

TC-780 VHF PCB View ..........................................................................................................................41

TC-780 UHF PCB View ..........................................................................................................................41

TC-780 VHF/UHF PCB View..................................................................................................................41

TC-780 Block Diagram ...........................................................................................................................41

TC-780 VHF Schematic Diagram ...........................................................................................................41

TC-780 UHF Schematic Diagram...........................................................................................................41

TC-780 VHF/UHF Schematic Diagram...................................................................................................41

Specifications .........................................................................................................................................42

TC-780 Service Manual

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.

zThis equipment should be serviced by qualified technicians only.

zUse only HYT supplied or approved antenna.

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

zTo avoid electromagnetic interference and/or compatibility conflicts, turn off your radio in any

facility where posted notices instruct you to do so.

zWhen instructed to do so, turn off your radio when on board an aircraft. Any use of a radio must

be in accordance with airline regulations or crew instructions.

zTo 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.

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.

zDo 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.

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

zIf 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.

TC-780 Service Manual

Radio Overview

○

1 PTT (Push-to-Talk) Key ○

2 SK1 (Side Key 1) ○

3 SK2 (Side Key 2) ○

4 Antenna

○

5 Microphone ○

6 Speaker ○

7 LCD Display ○

8 Function Keypad

○

9 Numeric Keypad ○

10 TK (Top Key) ○

11 Channel Selector

Knob

○

12 Radio On-Off

/Volume Control Knob

○

13 LED Indicator ○

14 Accessory Jack ○

15 Battery Latch ○

16 Belt Clip

○

17 Battery ○

18 Screw, Belt Clip ○

19 Charging Piece

﹡PTT (Push-to-Talk) Key

Press and hold down the PTT key to transmit; release it to receive.

﹡SK1 (Side Key 1)

TC-780 Service Manual

Programmable function key.

﹡SK2 (Side Key 2)

Programmable function key.

﹡LCD Display

Used to display radio status information.

﹡Function Keypad

zExit key

Use the Exit key to return to the previous menu.

zUp key

zDown key

zMenu/Select key

Used to enter the menu mode. When you are in the menu mode, this key is also used to make menu

selections.

Exit Up Menu/Select

Call Back Down Redial

﹡Numeric Keypad

Used to enter information for programming the radio’s lists.

﹡TK (Top Key)

TC-780 Service Manual

Programmable function key.

﹡Channel Selector Knob

Rotate the knob to select a desired channel.

﹡Radio On-Off/Volume Control Knob

Rotate the knob clockwise to turn the radio on, and 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.

﹡LED Indicator

The following table indicates LED mode and corresponding radio status:

Status LED

Transmit Red

Receive Green

Low battery alert Flash red

After transmitting a call (within auto reset time) Orange

After receiving a call (within auto reset time) Flash orange slowly

Missed call alert Flash orange rapidly

Scan Flash green

﹡Accessory Jack

The jack is used to connect audio accessories, or other accessories such as programming cable.

TC-780 Service Manual

Software Specifications

Specifications

z256 Conventional Channels

z32 Channel Groups

z2-Tone/DTMF/HDC1200/HDC2400TM Encode & Decode

zATIS Encode

zPriority Channel Scan

When the radio operates in talkaround mode, the channel scan feature provides users with an easy way

to monitor and join other channels.

a) Revert Channel

Press of the PTT during radio scanning shall cause the radio to transmit on the programmed revert

channel.

b) Nuisance Channel Delete

To ensure accurate scanning, press the Nuisance Channel Delete key to temporarily remove the

nuisance channel from the current scan list.

zBusy Channel Lockout

A channel already in use is not available to other users.

zProgrammable Function Buttons

Six of the radio’s buttons can be programmed as shortcut buttons for your most often used features.

zTime-out Timer

The feature allows for more efficient use of channels by limiting the amount of time of each transmission.

The range is from 15 seconds to 600 seconds.

zEmergency

Press the Emergency key to emit emergency alarm, or send ENI (Emergency Number Identity) /

background tone to a pre-defined person or the dispatch center, whichever is defined by the Emergency

option. Press the button again to cancel the emergency procedure.

zVOX

zDual Home Channels

zOptional Functions

a) Man Down

TC-780 Service Manual

b) External Scrambler

c) Patrol Record

d) GPS Function

Description

1. User Mode

This mode is for normal operation by end users.

2. All Reset Mode

Allows you to initialize tuning items, channel frequency, and conventional functions. See the

Adjustment Description section for details.

3. Clone Mode

a) Factory Wired Clone Mode

b) Dealer Wired Clone Mode

c) Factory Wireless Clone Mode

d) Dealer Wireless Clone Mode

Press SK1 and to enter clone mode; press SK2 to toggle between wired and wireless clone modes;

press TK to toggle between factory and dealer modes.

4. Manual Adjust Mode

Allows you to adjust frequency deviation, power level, sensitivity, squelch level, and etc.

5. PC Adjust Mode

Allows you to adjust the radio manually or automatically via PC.

Circuit Description

Circuit Composition

The overall circuit is composed of PLL-VCO circuit, transmit circuit, receive circuit, baseband processing

Note: You must select

Manual Adjust Mode

from Optional Features

in the programming

software, before you

can enter manual

TC-780 Service Manual

circuit, power supply circuit, and MCU control circuit.

Frequency Configuration

The receiver section utilizes double conversion. The first IF is 44.85MHz and the second IF is 455 KHz.

The first local oscillator signal is supplied by PLL and VCO circuit. The second local oscillator signal is

generated from TCXO (44.395MHz); The PLL and VCO circuit also generates the frequencies required

by the transmit section.

1. Receive Circuit

Configuration of the receive circuit is shown in Figure 1.

Figure 1 Receive Circuit

2. RF AMP BPF

The signal from antenna is amplified at RF amplifier (Q410) after passing through a

transmit/receive switch circuit and a band pass filter. The amplified signal is filtered by a band

pass filter to eliminate unwanted signals before it goes to the first mixer.

3. The First Mixer

The signal output by RF AMP BPF is mixed with the first local oscillator signal output by PLL frequency

synthesizer at the first mixer (Q415) to create a 44.85 MHz first IF signal. The first IF signal is then fed

through a crystal filter (XF401) to further remove spurious signals.

4. IF Amplifier

The first IF signal is amplified by Q412 and then enters U403 (TA31136FN). The signal is mixed with the

TC-780 Service Manual

second local oscillator signal (44.395MHz) again to create a 455 KHz second IF signal, which passes

through a ceramic filter (wide band: Z404; narrowband: Z403) to eliminate unwanted signals. The

resulting signal is detected by U403 to output audio signal from Pin 9.

5. Audio Amplifier

The Rx audio signal output by U403 is amplified by U201, and then passes through the audio processor

U203 (the received signalling is separated from the signal for decoding). The amplified signal then is fed

to AF MUTE, volume switch SW601 (volume control) and Q615 (PA MUTE control). The resulting signal

is finally fed to the audio amplifier U609 to output audio signal from speaker.

6. Squelch

Noise signal is derived from the Rx audio signal output by Pin 9 of U403, and is processed by U403 to

produce an SQL level. The SQL level is then compared in CPU (U605) to generate a level which controls

AF MUTE and PA MUTE. It controls Q204 and Q615 to enable or disable the audio path.

Transmit Circuit

The transmit circuit is composed of MIC circuit, frequency synthesizer, driver and final-stage power

amplifier circuit, and the APC circuit.

Figure 2 Transmit Circuit

TC-780 Service Manual

1. MIC Circuit and Modulation Circuit

The audio signal from microphone is amplified by U204 after passing through the MIC control switch

(Q616). The resulting signal is then amplified, pre-emphasized and etc by U203. Simultaneously,

DTMF/2-Tone/5-Tone signallings generated by the MCU are amplified by U203, and then mixed with

MIC audio signal, and finally fed to VCO for modulation.

2. Driver and Final-Stage Power Amplifier Circuit

RF signal from local oscillator circuit is amplified by Q401 and Q402. The amplified signal is fed to the

driver stage Q404 and then the final-stage power amplifier (Q409) for amplification. The resulting signal

then passes through LPF to filter harmonics before reaching the antenna for transmit.

3. APC

The automatic power control (APC) circuit stabilizes the transmit power by detecting the drain current of

final-stage amplifier.

Frequency Synthesizer

PLL-VCO circuit generates frequency for receiving the first local oscillator signal and transmitting signals.

PLL-VCO circuit consists of Tx frequency oscillator (Q103), Rx frequency oscillator (Q101), buffer

amplifier (Q105), RF amplifier (Q107), PLL IC (U101), second harmonic circuit (Q108 and Q109) and

Tx/Rx VCO control switch (Q111, Q112, Q110 and Q102).

In transmit mode, IC120 transmits the operating frequency data to PLL IC. PLL IC is turned on to activate

Tx VCO. The outputted signal is amplified by Q703, Q124, and then divided by PLL IC (step: 2.5 KHz or

5 KHz, 6.25 KHz). The divided signal is compared with the reference signal from 16.8MHz crystal

oscillator X101 (frequency stability: 2.5ppm) in the phase comparator. The frequency control voltage

output from the phase comparator controls Tx VCO after passing through LPF. In the meantime,

modulation signal (Tx) is passed to Tx VCO for frequency modulation.

The working principle in receive mode is similar to that in transmit mode.

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