Kenwood TKR-750 Service manual

VHF FM REPEATER

TKR- 750

SERVICE MANUAL

Knob (DC source) (K29-9106-04)

Panel (Outer) (A62-0840-03)

Panel assy (A62-0934-03)

CONTENTS

GENERAL .................................................. 2

Knob (VOL) (K29-5389-03)

Key top (K29-5460-02)

Modular jack (E08-0543-05)

TERMINAL FUNCTION ........................... 47

SYSTEM SET-UP ...................................... 2

OPERATING FEATURES .......................... 3

REALIGNMENT ....................................... 11

INSTALLATION ....................................... 13

MODIFICATION....................................... 15

DISASSEMBLY FOR REPAIR ................. 16

CIRCUIT DESCRIPTION .......................... 17

SEMICONDUCTOR DATA ...................... 23

DESCRIPTION OF COMPONENTS ........ 25

PARTS LIST ............................................. 27

EXPLODED VIEW.................................... 37

PACKING ................................................. 39

ADJUSTMENT ........................................ 40

WIRING .................................................... 51

PC BOARD VIEWS

RX PLL/VCO (X58-4780-10) ................ 53

TX PLL/VCO (X58-4790-10) ................ 54

DISPLAY UNIT (X54-3330-20) ............ 55

FINAL UNIT (X45-3620-XX) ................ 59

TX-RX UNIT (X57-6260-XX) (A/2)...... 65

TX-RX UNIT (X57-6260-XX) (B/2) ...... 71

SCHEMATIC DIAGRAM .......................... 77

BLOCK DIAGRAM ................................... 89

KES-4 (EXTERNAL SPEAKER) ............... 92

SPECIFICATIONS .................................... 93

TKR- 750

GENERAL / SYSTEM SET-UP

INTRODUCTION

SCOPE OF THIS MANUAL

This manual is intended for use by experienced technicians familiar with similar types of commercial grade communications equipment. It contains all required service information for the equipment and is current as of the publication date. Changes which may occur after publication are covered by either Service Bulletins or Manual Revisions. These are issued as required.

ORDERING REPLACEMENT PARTS

When ordering replacement parts or equipment information, the full part identification number should be included. This applies to all parts : components, kits, or chassis. If the part number is not known, include the chassis or kit number of which it is a part, and a sufficient description of the required component for proper identification.

SYSTEM SET-UP

PERSONNEL SAFETY

The following precautions are recommended for person-

nel safety :

• DO NOT transmit until all RF connectors are verified secure and any open connectors are properly terminated.

• SHUT OFF and DO NOT operate this equipment near electrical blasting caps or in an explosive atmosphere.

• This equipment should be serviced by a qualified technician only.

SERVICE

This radio is designed for easy servicing. Refer to the

schematic diagrams, printed circuit board views, and alignment procedures contained in this manual.

Merchandise

received

Choose the type

of transceiver

Repeater

programming & setup

DC power supply or duplexer?

External speaker?

Delivery

Frequency range (MHz)

TX/RX 146~174 TX/RX 136~150

See page 11. A personal computer (IBM PC or compatible), programming interface (KPG-46), and programming software (KPG-66D) are required for programming.

YES

Installation in the

optional space

YES

KES-4 installation

RF power

50W 50W

Type

K,E

1. Controls and Functions

1-1. Front Panel

OPERATING FEATURES

TKR- 750

3 4 52

9 8 7 6

1 Speaker

2 CH/STATUS Display

Two, 7-segment digits display the channel number or status.

3 VOLUME control

Rotate to adjust the volume.

4 DC source switch

5 Dc source indicator

Lights green when DC source is applied from the DC

13.6V jack (DC 13.2V jack on E type versions). Lights red when DC source is applied from the BACK UP battery terminal.

6 MIC jack

Connect a microphone to this 8-pin modular jack.

1-2. Rear Panel

2 8 3 4 9

7 Programmable Function keys

Press these keys to activate their programmable functions.

PF1 key (left side) Default : None (No function)

PF2 key Default : Repeat disable/enable

PF3 key Default : TX disable/enable

PF4 key Default : Take over

PF5 key Default : Monitor on/off

PF6 key (right side) Default : Channel up

8 BUSY indicator

Lights green while a signal is being received.

9 TX indicator

Lights red while transmitting.

7 6 5

1 TX OUT jack

Connect a TX antenna or a duplexer to this receptacle.

2 CONTROL I/O jack

Connect an external programming device or repeater controller to this DB-25 interface.

3 FUSE

Insert 15 A blade fuses into these fuse holders.

4 RX IN jack

Connect a RX antenna or a duplexer to this BNC receptacle.

5 DC 13.6V (K type) / DC 13.2V (E type) jack

Connect a 13.6 V (K type) or 13.2 V (E type) DC power supply to this jack.

6 BACKUP battery terminal

7 TEST/SPKR jack

Test input/output jack. Connect an external speaker to this jack.

8 Cooling fan

9 Optional space

For external DC power supply, or duplexer, etc.

TKR- 750

OPERATING FEATURES

2. Two 7-segment LED displays

• Channel display (1~16) : While operating normally in user mode.

• When the displayed channel is contained in scan sequence, the right side decimal point is displayed.

• When the displayed channel is the priority channel, the left side decimal point is displayed.

• “E2” is displayed when the channel data is not written.

• “E3” is displayed when PLL is unlocked. Receiver PLL unlocked = flashing BUSY LED. Transmitter PLL unlocked = flashing TX LED.

• “E4” is displayed when PTT is attempted on a channel number that has no frequency data programmed.

• “PC” is displayed while in PC mode.

• “PG” is displayed while in firmware programming mode. 2 decimal points displayed = 115,200bps 1 decimal point displayed = 57,600bps No decimal = 38,400bps

• “E1” is displayed when FPU data is not written.

• “SC” is displayed while in scan mode.

TKR- 750

OPERATING FEATURES

3. Programmable Functions

TKR-750 contains many Programmable Functions tabled below.

Programmable Function Description

AUX Out 1~5 Off AUX Out 1 to 5 ports become deactivated, respectively.

AUX I/O 1~6 Off AUX I/O 1 to 6 ports become deactivated, respectively.

AUX Out 1~5 On AUX Out 1 to 5 ports become activated, respectively.

AUX I/O 1~6 On AUX I/O 1 to 6 ports become activated, respectively.

AUX Out 1~5 On/Off AUX Out 1 to 5 ports are toggled between its active and inactive states, respectively.

AUX I/O 1~6 On/Off AUX I/O 1 to 6 ports are toggled between its active and inactive states, respectively.

Channel 1~16 Directly select Channel 1 to 16, respectively.

Channel Down The channel decrements by one.

Channel Up The channel increments by one.

CW ID On The CW ID is transmitted.

CW Message 1~8 On The CW Message 1 to 8 is transmitted, respectively.

Display Off All panel LEDs are turned off except the Power LED.

Display On All panel LEDs become active as normal status indicators on the repeater.

Display On/Off All panel LEDs, with the exception of the Power LED, are toggled between off and their normal status on

the repeater.

Hold Time Enable The Parameter of Repeat Hold Time is enabled.

Hold Time Disable The Parameter of Repeat Hold Time is disabled.

Hold Time Disable/Enable The Parameter of Repeat Hold Time is toggled between disabled and enabled.

Local Tx Disable The local mic’s PTT is disabled.

Local Tx Enable The local mic’s PTT is enabled.

Local Tx Disable/Enable The local mic’s PTT is toggled between disabled and enabled.

Monitor Off The QT/DQT decoder is disabled.

Monitor On The QT/DQT decoder is enabled.

Monitor On/Off The QT/DQT decoder is toggled between disabled and enabled.

Monitor Momentary The QT/DQT decoder is momentarily disabled.

Multi Table Sub Multi Table No. Select Signalling changes to the Multi Table Sub.

Multi Table Main Multi Table No. Select Signalling changes to the Multi Table Main.

Multi Table Main/Sub Multi Table No. Select Signalling changes between Multi Table Sub and Multi Table Main.

QT/DQT Dec Disable Disables the QT/DQT decode operation.

QT/DQT Dec Enable Enables the QT/DQT decode operation.

QT/DQT Dec Disable/Enable Toggles between disabling and enabling the QT/DQT decode operation.

QT/DQT Enc Disable Disables the QT/DQT encode operation.

QT/DQT Enc Enable Enables the QT/DQT encode operation.

QT/DQT Enc Disable/Enable Toggles between disabling and enabling the QT/DQT encode operation.

Repeat Disable Disables repeater operation.

Repeat Enable Enables repeater operation.

Repeat Disable/Enable Toggles between disabling and enabling repeater operation.

Reset Resets to default condition set up by FPU.

DC Power Save Off Activates DC Power Save Mode Off.

DC Power Save On Activates DC Power Save Mode On.

DC Power Save On/Off Toggles between DC Power Save Mode On and Off.

TKR- 750

OPERATING FEATURES

Programmable Function Description

Scan Off Inhibits scanning.

Scan On Starts scanning.

Scan On/Off Scanning is toggled between being enabled or inhibited.

Scrambler Off Disables an installed optional voice scrambler board.

Scrambler On Enables an installed optional voice scrambler board.

Scrambler On/Off Toggles between enabling and disabling an installed optional voice scrambler board.

Squelch Off The Squelch unmutes.

Squelch On The Squelch mutes.

Squelch On/Off The receiver’s squelch toggles between muted and unmuted.

Squelch Momentary The Squelch momentarily unmutes.

Take Over On/Off Toggles between disabling and enabling remote wireline control.

Test Tone Off The Test Tone is inhibited.

Test Tone On The Test Tone is enabled.

Test Tone On/Off Toggles between enabling and inhibiting the Test Tone.

TOT Disable The Time Out Timer is disabled.

TOT Enable The Time Out Timer is enabled.

TOT Disable/Enable The Time Out Timer is toggled between disabled and enabled.

TX Disable The transmitter is inhibited.

TX Enable The transmitter is enabled (normal).

TX Disable/Enable Toggles between transmitter inhibited and transmitter enabled (normal).

The following Programmable Functions are output functions used to tell the condition of the TKR-750 to an external device.

The output functions can be assigned to only AUX Outputs as follows.

Programmable Function Description

COR (Carrier Operate Relay) This function becomes valid if an RF carrier is present.

TOR (Tone Operate Relay) This function becomes valid if an RF carrier and the specified QT/DQT are present.

RX Unlock This alarm function becomes valid if the RX PLL circuitry becomes unlocked.

TX Unlock This alarm function becomes valid if the TX PLL circuitry become unlocked.

Power Supply Lower Limit This alarm function becomes valid if the DC power supply voltage becomes less than the preset point.

The preset point is selected in the range of 10.6V to 13.6V.

TXS (TX Sense) This function becomes valid when the transmitter is keyed.

Selectable AUX Outputs which are set up as Selectable appear in the available Function List for the AUX Input

Functions and Key Assignment.

This allows AUX Inputs and PF Keys to be used to control AUX Outputs.

RX Signal Detect This function becomes valid if the RX signal level becomes less than the preset point. The preset point is

selected in the range of –120dBm to –95dBm.

RF Power Down Detect This alarm function becomes valid if the RF Power becomes less than about 10W.

Fan Status This alarm function becomes valid when the Fan is turned on, either by sensing a high temperature

condition or by its operating mode being set to Continuous.

TKR- 750

OPERATING FEATURES

4. Trigger Assignment

The Programmable Functions described above can be assigned to PF keys, AUX input, Save on/off, Start up, and Power supply

according to following table.

In the last column of the table, when the Programmable Functions is assigned to any PF keys, it expresses that the LED in the

PF key turns on either conditions. “Yes” expresses that the trigger is available the Programmable Function. “No” expresses

that the trigger is not availabale the Programmable Function.

Trigger PF keys AUX Save Start up Power Condition of LED in he PF key on

Function input on/off supply

AUX Out 1~5 (I/O 1~6) Off No Yes Yes Yes Yes –

AUX Out 1~5 (I/O 1~6) On No Yes Yes Yes Yes –

AUX Out 1~5 (I/O 1~6) On/Off Yes Yes No No No Turns on in ON status.

Channel 1~16, Up/Down Yes Yes Yes Yes Yes Do not turn on.

CW ID On Yes Yes Yes Yes Yes Turns on while transmitting.

CW Message 1~8 On Yes Yes Yes Yes Yes Turns on while transmitting.

Display Off No Yes Yes Yes Yes –

Display On No Yes Yes Yes Yes –

Display On/Off Yes Yes No No No Turns on in ON status.

Hold Time Enable No Yes Yes Yes Yes –

Hold Time Disable No Yes Yes Yes Yes –

Hold Time Disable/Enable Yes Yes No No No Turns on in Disable status.

Local Tx Disable No Yes Yes Yes Yes –

Local Tx Enable No Yes Yes Yes Yes –

Local Tx Disable/Enable Yes Yes No No No Turns on in Disable status.

Monitor Off No Yes Yes Yes Yes –

Monitor On No Yes Yes Yes Yes –

Monitor On/Off Yes Yes No No No Turns on in ON status.

Monitor Momentary Yes No No No No Turns on in ON status.

Multi Table Sub No Yes Yes Yes Yes –

Multi Table Main No Yes Yes Yes Yes –

Multi Table Main/Sub Yes Yes No No No Turns on in Sub status.

QT/DQT Dec Disable No Yes Yes Yes Yes –

QT/DQT Dec Enable No Yes Yes Yes Yes –

QT/DQT Dec Disable/Enable Yes Yes No No No Turns on in Disable status.

QT/DQT Enc Disable No Yes Yes Yes Yes –

QT/DQT Enc Enable No Yes Yes Yes Yes –

QT/DQT Enc Disable/Enable Yes Yes No No No Turns on in Disable status.

Repeat Disable No Yes Yes Yes Yes –

Repeat Enable No Yes Yes Yes Yes –

Repeat Disable/Enable Yes Yes No No No Turns on in Disable status.

Reset Yes Yes No No No Do not turn on.

DC Power Save Off No Yes No Yes Yes –

DC Power Save On No Yes No Yes Yes –

DC Power Save On/Off Yes Yes No No No Do not turn on.

Scan Off No Yes Yes Yes Yes –

TKR- 750

OPERATING FEATURES

Trigger PF keys AUX Save Start up Power Condition of LED in he PF key on

Function input on/off supply

Scan On No Yes Yes Yes Yes –

Scan On/Off Yes Yes No No No Turns on in ON status.

Scrambler Off No Yes Yes Yes Yes –

Scrambler On No Yes Yes Yes Yes –

Scrambler On/Off Yes Yes No No No Turns on in ON status.

Squelch Off No Yes Yes Yes Yes –

Squelch On No Yes Yes Yes Yes –

Squelch On/Off Yes Yes No No No Turns on in OFF status.

Squelch Momentary Yes No No No No Turns on in OFF status.

Take Over On/Off Yes No No No No Turns on in ON status.

Test Tone Off No Yes Yes Yes Yes –

Test Tone On No Yes Yes Yes Yes –

Test Tone On/Off Yes Yes No No No Turns on in ON status.

TOT Disable No Yes Yes Yes Yes –

TOT Enable No Yes Yes Yes Yes –

TOT Disable/Enable Yes Yes No No No Turns on in Disable status.

TX Disable No Yes Yes Yes Yes –

TX Enable No Yes Yes Yes Yes –

TX Disable/Enable Yes Yes No No No Turns on in Disable status.

None Yes Yes Yes Yes Yes Do not turn on.

5. Simplex/Duplex Operation

The Simplex/Duplex function is used to specify whether

the channel is used as simplex (receiver muted during transmit) or duplex (receiver unmuted during transmit). If the channel has same TX/RX frequency, it can operate only in Simplex mode.

6. Repeater/Base Station Operation

The Repeat function is used to specify whether the chan-

nel is used as a repeater or as a base station. A repeater simultaneously and automatically re-transmits its received audio, a duplex base station has independent simultaneous transmit and receive paths, a simplex base station are mutually exclusive transmit and receive paths.

7. Signalling Feature

7-1. Multiple QT/DQT

The TKR-750 can function as a multiple-QT/DQT decode/

encode unit for operation as a community repeater or multiple-QT/DQT base station. Two Multi Tables, called Main and Sub, can be created, each consisting of 16 decode/encode combinations.

The Multi Table function enables the TKR-750 to decode any one of the 16 QT/DQTs pre-programmed into the Multi Table. When receiving a signal (repeater operation), the repeater uses the QT/DQT encode which corresponds to the decoded QT/DQT as set in the Multi Table. In the Multi Table, signalling pair of “No.1” (first column) is defined as “Primary”. A receiving signalling (if it is contained within No.1 to No.16) is defined “Current”.

From No.2 to No.16, signalling pairs that can be changed between “Main Table” and “Sub Table” using AUX I/O Ports 1-4 are assigned as “Multi Table Select” and the Multi Table Main, the Multi Table Sub or the Multi Table Main/Sub function is executed. When AUX I/O Ports 1~4 are set for “Multi Table Select”, these are 4 bit Binary Coded Decimal (BCD) inputs .AUX I/O 1 is a least significant bit (LSB), and “1101” input (LSB on the right side) signifies the Table No.2 and “1100” input signifies the Table No.3.

7-2. Encode Tone in Multiple

When Local Microphone PTT or External PTT is active while the repeater is in use or the duplex-base station is receiving, the encode signalling is determined according to Encode Tone in Multiple function. The simplex-base station always transmits the “Primary” encode QT/DQT.

OPERATING FEATURES

TKR- 750

Current : When any PTT as described above is active while the repeater is in use or the duplex-base station is receiving, the “paired” encode QT/DQT associated with receiving QT/DQT is transmitted. When any PTT is active while the repeater or the duplex-base station is in idle period, the “Primary” encode QT/DQT is transmitted.

Primary : When any PTT (provided that the Priority of any PTT is higher than the Priority of Repeat PTT) is active while the repeater is in use, the encode QT/DQT changes “paired” encode QT/DQT to “Primary” while continuing to transmit. When any PTT is active while the repeater is in idle period, the “Primary” encode QT/DQT is transmitted. In the base station, the “Primary” encode QT/DQT is always transmitted regardless of the receiver status.

7-3. QT Reverse Burst Time

During repeat with QT tones, the repeater re-transmits a phase-shifted burst of the QT tone (“reverse burst”) when it detects the radio using the repeater has un-keyed and also sent a reverse QT burst (squelch-tail elimination). This mutes a receiving radio’s speaker audio before its receiver circuit shuts off causing squelch tail noise in the speaker audio. The TKR-750 can select the time between 140 to 200 ms that the QT reverse burst is sent. Typically this time should not have to be adjusted from the default value. The transmission of the QT reverse burst can be also inhibited if the QT Reverse Burst function is set to “No”.

7-4. DQT Turn Off Code Time

During repeat with DQT tones, the repeater re-transmits a specific turn-off code when it detects the radio using the repeater has un-keyed and also sent the turn-off code (squelch-tail elimination). This mutes a receiving radio’s speaker audio before its receiver circuit shuts off causing squelch tail noise in the speaker audio.

The TKR-750 can select the time between 140 to 200ms that the DQT turn-off code is sent. Typically this time should not have to be adjusted from the default value.

1) if a RF carrier and a valid QT/DQT is present. The receiving channel number is displayed and the received audio is heard from a speaker.

2) if a RF carrier is present, providing that the Monitor On function is executed.

3) if the Squelch Off function is executed. Scanning stops on the channel being scanned when Squelch Off is executed, the channel number is displayed and the received audio is heard from a speaker.

4) if a local microphone’s hook is in off hook status, providing that the Off Hook Scan function is set to Disable. Scanning stops on the Revert channel, but the audio is not heard until a valid signal is received.

When the received call is ended, scanning automatically

resumes after the period set in Dropout Delay Time function has expired. When the Scan Off function is executed, the TKR-750 inhibits scanning and displays the selected channel.

8-2. Scan Sequence

1) Normal Scan : When no Priority channel is set, scanning of ADD channels is done in ascending order.

2) Single Priority Scan : The Priority channel is set as either a fixed channel or a selected channel. When Priority channel is set, Priority channel and non Priority channel are scanned by turns. When scanning stops on the non Priority channel, calls from the Priority channel are still checked at set intervals while scanning is stopped. This operation is called Look Back and the interval period is selected by the Look Back Time function.

8-3. Revert Channel

The Revert channel is a channel that is used to transmit

during scanning. The time from the end of transmission on Revert channel to the time scanning automatically resumes is set in Dwell Time function. The Revert channel types are Last Called, Last Used, Selected, Selected + TalkBack, Priority, and Priority + TalkBack.

7-5. Off Hook Decode

The TKR-750 is able to decode QT/DQT regardless whether the local microphone is in the on- or off-hook condition. When the Off Hook Decode function is enabled, the TKR-750 is capable of QT/DQT decode even though the microphone is in the off-hook condition (or a local microphone is not installed).

8. Scan Feature

8-1. Scan Operation

Providing that the TKR-750 contains two or more non-priority ADD channel or one or more non-priority ADD channel and Priority channel, it starts scanning once the Scan On function is executed and displays “SC” on the 7-seg LED. Scanning stops temporarily if any following conditions be come valid.

1) Last Called : The TKR-750 reverts to the channel upon which a call was last received even if scanning has resumed (power on default = selected channel).

2) Last Used (with TalkBack) : The TKR-750 reverts to the channel that was last transmitted on (power on default = selected channel). However, if a call is received on a channel other than the last transmit channel and PTT is pressed before scanning resumes, the transceiver “talks back” on the current receive channel.

3) Selected : The transceiver reverts to the channel set by the function prior to scan initiation.

4) Selected+TalkBack : The TKR-750 reverts to the channel set by the Channel ‘X’ functions or Channel Select function prior to scan initiation. However, if a call is received on a channel other than the selected channel and PTT is pressed before scanning resumes, the transceiver “talks back” on the current receive channel.

5) Priority : The TKR-750 always reverts to the Priority channel.

TKR- 750

OPERATING FEATURES

6) Priority+TalkBack : The TKR-750 always reverts to the Priority channel. However, if a call is received on a channel other than the Priority channel and PTT is pressed before scanning resumes, the transceiver “talks back” on the current receive channel.

9. CW ID and Message

The TKR-750 contains internal automatic station identifi-

ers. The CW ID (Morse code) is set and transmitted on a per-channel basis. The CW ID is transmitted when the interval period is reached (TX Interval Time function), the channel is changed (CW ID on Channel Change function) or CW ID Onfunction is executed. When CW ID is activated by any functions described above, it is actually sent after the total time of TX Delay Time (not applied to CW ID On function) and CW Modulation Delay Time has expired. TX Delay Time is a period from CW ID is activated to the transmitter is keyed.

CW Modulation Delay is a period from the transmitter is

keyed to the CW ID tone is sent. The CW ID tone is routed to the Receive Audio (RA) port and a speaker if the Send CW ID to RA function is set to Yes. The TKR-750 contains 8 message banks for CW Message. CW Message 1 to 8 is transmitted on the current channel when the CW Message 1 to 8 On function is activated, respectively.

10. PTT Priority

A number of keying sources can be used to cause the

TKR-750 to transmit.

The transmit audio path is switched according to their

keying sources and when PTTs is simultaneously activated, the transmit audio path related to the PTT with higher priority is given priority. These are Local Microphone PTT, External PTT, and Repeat PTT.

11. Time Out Timer

The Time Out Timer function determines the period of

time users can continuously transmit. When the selected period expires, the transmission is inhibited.

12. Repeat Hold Time

The Repeat Hold Time (hang timer) function is used to

prevent the repeater from being repeatedly keyed and unkeyed in response to short message traffic. When a mobile transceiver unkeys, the repeater’s Hold Timer allows the repeater to continue transmitting for a brief period while waiting for a responding end user. If no valid QT/DQT is detected within the Hold Timer period, the transmitter is allowed to unkey. This function determines the period of time that the transmitter is allowed to remain keyed after the loss of a valid QT/DQT received signal.

13. Take Over

The Take Over function is used to disable the external wireline control of the repeater. When Take over function is enabled, the external AUX inputs and Outputs, transmit audio inputs and receive audio outputs, External PTT and External Monitor lines are disabled. All AUX Input functions assigned to any AUX Input stay in their current state. However External PTT and External Monitor switch to the “Off” state.

14. Test Tone

The Test Tone is a single-frequency audio sine wave and is turned On and Off by toggling Test Tone On/Off functions. The transmitter can be modulated without a local microphone by using the test tone. When Test Tone On function is executed and any PTT is activated, the TKR-750 transmits the test tone with mic mute and also routes the test tone to RA port.

15. RF Power

The TKR-750 is able to switch transmission output on a per-channel basis. When the TX High Power function is enabled, the transmission output is set to high power.

16. Fan Action

The TKR-750 has a cooling fan. The Fan Action function determines whether the fan is continuously operated or operates in response to high temperatures only.

17. AUX Input and Output

There are 6 programmable AUX I/O Ports 1~6 (pins 20~25) and 3 programmable AUX Input Ports 1~3 (pins 4~6) on the rear 25 pin D-Sub connector (CONTROL I/O) and 5 programmable AUX Output Ports 1~5 (pins 10, 11, 13~15) on the rear 15 pin TEST/SPKR connector.

The 6 programmable AUX I/O pins are primarily intended for remote control interfaces. Each AUX I/O Port can be set for AUX Input, AUX Output, remote Channel Select or Multi Table Select types. The AUX Input Port can be set execute a single input function or a set of up to three functions when the port is activated. If the port type for an AUX I/O Ports 1~6 is set for “AUX Input”, it will also appear AUX Input window for function programming. The input logic is fixed as active Low.

The AUX Output Port can be set execute a single output function. If the port type for an AUX I/O Ports 1~6 is set for “AUX Output”, it will also appear AUX Output window for function programming. The output logic of AUX Output can be set as either active High or active Low by the Logic Type function. Active High outputs a High (5V) when the programmed condition becomes valid, active Low outputs a Low (0V) when the condition becomes valid.

OPERATING FEATURES / REALIGNMENT

User mode

PC mode

Firmware Programming mode

PC programming mode

PC test mode

PC tuning mode

TKR- 750

18. Channel Select

AUX I/O Ports 1~4 (1 or all 4) can each be set for “Channel Select” providing up to 16 channel selection capability. These are 1 to 4 bit Binary Coded Decimal (BCD) inputs. AUX I/O 1 is a least significant bit (LSB). When all of AUX I/ O Ports 1~4 set to Channel Select, “1110” input (LSB on the right side) signifies the Channel 1 and “1101” input signifies the Channel 2.When the Channel Select function is set to any AUX I/O ports, the Channel ‘X’ function (Channel Up, Channel Down, Channel 1, etc.)can not be set to the AUX Input ports, but can be set to the PF Keys. Normally the channel control is controlled by the Channel Select function. If the Take Over function is executed, the channel control is disabled to be controlled by the Channel Select and enabled to be controlled by the PF Keys.

19. DC Power Save

The TKR-750 has the DC Power Save feature. The DC Power Save Mode is activated when the DC Power Save On function is executed. When the DC Power Save Mode is activated, all panel LEDs except the Power LED are turned off, and the audio amplifier and the DSP becomes inactive. When the Display On function is executed while the repeater is in the DC Power Save Mode, all panel LEDs become active as normal status indicators on the repeater, and the audio amplifier and the DSP becomes active. However, when the Save Delay Timer A period expires, all panel LEDs except the Power LED are turned off and the audio amplifier becomes inactive again, and when the Save Delay Timer B period expires, the DSP becomes inactive. When the DC Power Save Mode is turned on or off, up to 3 functions preprogrammed into the Save On function or Save Off function are executed in sequence.

20. Power Supply

The TKR-750 is able to use two Power sources that are called Main and Backup. When the Power source changes from Main to Backup or from Backup to Main, up to 3 functions pre-programmed into the Backup Power function or the Main Power function are executed in sequence.

21. Start Up

When the TKR-750 is first turned on or is reset, up to 3 functions pre-programmed into the Start Up function are executed in sequence.

22. Optional Board

An optional scrambler board can be installed in the TKR-

750. Scrambler codes between 1 and 16 are available per channel. If the scrambler board is not to be used (although it is installed), set the parameter to “Off”. When any Scrambler code is set up and the Scrambler On function is executed, the scrambler board is activated.

REALIGNMENT

1. Modes

Mode Function

User mode Use this mode for normal operation.

PC mode Use this mode to make various settings by

means of the FPU through the RS-232C port.

PC programming Use to read and write frequency data and

mode other features to and from the repeater.

PC test mode Use to check the repeater using the PC.

This feature is included in the FPU.

Firmware pro- Use when changing the firmware program

gramming mode of the flash memory.

2. How to Enter Each Mode

Mode Operation

User mode Power on.

PC mode Received commands from PC.

Firmware Pro- [PF1] key + Power on (one second).

gramming mode

3. PC Mode

3-1. Preface

The TKR-750 repeater is programmed by using a personal

computer, programming interface and KPG-66D software.

3-2. Connection Procedure

1. Connect the TKR-750 to the personal computer with the interface cable.

2. When power is applied, the user mode is entered immediately. When the PC sends a command, the repeater enters the PC mode and displays “PC” on the 7-segment LED. When data is being transmitted to the PC from the repeater, the TX LED flashes. The BUSY LED flashes when data from the PC is being received by the repeater.

Note :

• The data stored in the personal computer must match the model type, when it is written into the flash memory.

• Change the TKR-750 to PC mode, then attach the interface cable.

TKR- 750

REALIGNMENT

3-3. KPG-46 Description (PC Programming Inter-

face Cable : Option)

The KPG-46 is required to interface the TKR-750 to the computer. It has a circuit in its D-sub connector (25-pin) case that converts the RS-232C logic level to the TTL level.

The KPG-46 connects the microphone connector of the TKR-750 to the computer’s RS-232C serial port.

3-4. Programming Software Description

The KPG-66D programming disk is supplied in 3-1/2" disk format. The software on the disk allows a user to program TKR-750 repeater via the programming interface cable (KPG-

46).

3-5. Programming With IBM PC

Data can be programmed into the flash memory in RS232C format via the microphone connector.

IBM PC

KPG-46

KPG-66D

TKR-750

Fig. 1

4. Firmware Programming Mode

4-1. Preface

The TKR-750 uses flash memory to allow it to be easily

upgraded when new features are released in the future.

4-2. Connection Procedure

Connect the TKR-750 to the personal computer (IBM PC or compatible) with the interface cable (KPG-46). (Connection is the same as in the PC mode.)

Notes :

You can only program firmware from the 8-pin microphone connector on the front panel. Using the 25-pin logic interface on the rear panel will not work.

4-3. Programming

1. Start up the programming software (Fpro. exe).

2. Set the communications speed (normally, 115200 bps)

and communications port in the configuration item.

3. Set the firmware to be updated by file name item.

4. Turn the TKR-750 power on with the [PF1] key held

down. Hold the key down for one second until the 7-

segment display changes to “P.G.”. When “P.G.” ap-

pears, release your finger from the key.

5. Check the connection between the TKR-750 and the per-

sonal computer, and make sure that the TKR-750 is in the

program mode.

6. Press write button in the window. A window opens on

the display to indicate progress of writing.

7. If writing ends successfully, the TX LED on the TKR-750

lights.

8. If you want to continue programming other TKR-750s,

repeat steps 3 to 6.

Notes :

This mode cannot entered if the firmware program mode is set to disable in the programming software (KPG-66D).

4-4. Function

If you press the [PF1] key (front panel), both decimal point on the 7-segment display will disappear. The writing speed is 38400 bps (low-speed mode). If you press the [PF1] key again, the right hand decimal points will light. The writing speed is 57600 bps (middle-speed mode).

Note :

Normally, write in the high-speed mode (115200 bps).

INSTALLATION

CN606

CN604

CN605

CN601

114

R653

R742

TX-RX unit (B/2) control section Component side

PTO

Display unit Foil side

TXI (MIC signal input)

TXO (MIC signal output)

RXI (RX audio signal input)

AC (Audio control signal output)

BC1 (Scramble code output 1) BC2 (Scramble code output 2) BC3 (Scramble code output 3) BC4 (Scramble code output 4)

PTI (PTT signal input)

CLRC (Clear code for scrambler)

DEO (Detection signal output)

PTO (PTT signal output)

5C (5V output)

GND

CN601

Voice

scrambler

Display unit

1. External Power Supply Connection

(Rear Connectors) : See Page 3

This unit has two external power supply connectors :

Main DC and Backup.

If an external DC power supply is connected to the main DC connector and a backup battery is connected to the Backup connector at the same time, the DC power supply switches to the battery automatically if power failure occurs. Therefore, the operation of the repeater can be continued.

If the battery is used, but both the battery and power supply need not be connected (if an external switch is used or if only a solar battery is used), connect it to the Backup connector, not the Main DC connector. Current consumption can be reduced by approx. 120mA because the relay is not used.

If it is installed when the temperature at the repeater site is below freezing, check whether the switch (relay) works properly after installation.

2. Voice Scrambler

It operates only during base operation. The voice is not scrambled when it is repeated.

TKR- 750

Fig. 1

2-1. Modification

1) Remove R742 and R653 on the TX-RX unit (B/2) : control

section.

2-2. Connection

1) The functions of pins of CN601 on the TX-RX unit (B/2) :

control section are shown in the figure.

2) Join the CN601 connector to the voice scrambler board

via the E37-0808-05 connector cable.

When the operation is checked in PC test mode after the modification, and the maximum deviation is adjusted, the voice from the local microphone is not modulated. In this case, remove the CN601 12-pin (PTO) cable and connect it to the land of the display unit (X54-333) from the voice scrambler. The voice from the local microphone can be modulated in PC test mode.

Fig. 2

Fig. 3

TKR- 750

3. External Speaker (KES-4)

The TKR-750 has a internal built-in speaker (5W/8Ω), and

the external speaker output from the TEST/SPKR connector

(15-pin) on the rear of the radio is 4W/4Ω. Use external

speaker KES-4.

3-1. Connection for the KES-4 With the TKR-750

■ When taking the AF output from the TEST/

SPKR connector (15-pin) on the rear of the radio

The following tools are required for changing the connec-

tor.

• Extracting tool

The following extracting tool is recommended : Molex Inc. Order No. : 11-03-0002

1. Remove the connector with jumper from the external speaker connector on the rear panel of the radio. (Fig. 4-

1) Note : Save the jumper, which is required when the radio is used without the external speaker.

2. Remove the terminals with the jumper from the connector housing holes number 9 and 12 using the extracting tool.

Removing the jumper lead (Fig. 4-2)

1) Insert the extracting tool (11-03-0002) into the connector while pushing the jumper lead in the direction of (a).

2) Push the extracting tool into collapse the barbs of the crimp terminal.

3) Pull out the lead while continuing to push the extracting tool in the direction (b).

3. Reinsert the terminal with the black and white stripe lead into hole number 12, and the terminal with the black lead into hole number 6. (Fig. 4-3)

4. Attach the connector to the external speaker connector on the radio.

INSTALLATION

Fig. 4-1

Fig. 4-2

Note :

Relationship between TEST/SPKR connector (15-pin)

connection and speaker output.

When pins 9 and 12 are shorted : Built-in internal speaker

is used.

When pins 9 and 12 are open and output is from pins 6

and 12 : KES-4 is used.

Fig. 4-3

MODIFICATION

Modification for Sinking the Collector Current Up

Auxiliary output 1 and 2 can each be modified to sink up 600mA of the collector current. The following modification should be installed when Auxiliary output 1 or 2 is used to control external equipment.

1. Remove D625, R755, and R769 for Auxiliary output 1

(D624, R756, and R770 for Auxiliary output 2) on the

component side of the control section for TX-RX unit

PCB.

2. Install $Q608, $Q612, and $R761 for Auxiliary output 1

($Q607, $Q611, and $R759 for Auxiliary output 2) on the

component side of the control section for TX-RX unit

PCB.

$Q607, $Q608, $Q611, $Q612 : DTD114EKA

$R759, $R761 : 3.9kΩ (RK73GB1J392J) chip resistor.

3. Change R801 for Auxiliary output 1 (R797 for Auxiliary

output 2) from 1kΩ (RK73GB1J102J) to 0Ω (R92-1252-

05).

By making this modification, Auxiliary output 1 and 2 can now sink up to 600mA each.

TKR- 750

2. DC Source Switch

To prevent the power supply from turning off due to misoperation of the DC source switch on the front panel or accidents (tampering) after installation, the main unit can be kept on regardless of the on/off of the DC source switch on the front panel.

Short the PSW land near K1 relay by soldering.

TX-RX unit (A/2) Component side

CF1

WIDE

CF2

NARROW

Shift register IC623

TX-RX unit (B/2) Component side

IC602

IC623

Add $R761 ($R759)

3.9kΩ

Add $Q608 ($Q607) DTD114EKA

Remove R755 (R756) 0Ω

R756

$Q607

$R759

R770

R769

R755

$Q608 $Q612

$Q611

$R769

Fig. 1

5V 5V

Add $Q612 ($Q611) DTD114EKA

Remove R769 (R770) 0Ω

PSW

Fig. 3

CN605

C681

Remove D625 (D624) DA204U

TEST/ SPKR

Fig. 2

TKR- 750

MODIFICATION / DISASSEMBLY FOR REPAIR

3. Trickle Charge for Backup Battery

If the external DC power supply is connected to the Main DC connector and a backup battery (12V rechargeable type) is connected to the Backup connector at the same time, the battery can be trickle-charged from the external DC power supply with a maximum current of 0.5A.

Short the CHARGE land near R61.

Notes :

1. Make this modification after removing the DC power sup-

ply and battery for safety.

2. When the DC power supply is connected after the modi-

fication, DC voltage is output to the Backup connector.

Be careful during setup.

3. When the backup battery is used for a long time, remove

the battery from the repeater and recharge it because the

trickle charge is not sufficient for recharging a completely

discharged battery.

Final unit (A/2) Component side

DISASSEMBLY FOR REPAIR

How to Remove the Panel Assy (ABS)

Note : You can remove the panel assembly (ABS) without

removing the top panel (A62-0840-03).

1. To remove panel (TX-RX, ), loose 6 screws ( ).

2. To remove panel assembly (Front, ), loose 6 screws

().

3. The panel assembly (ABS) is security fastened by 4 tabs

( ) on top and bottom. You can remove the panel assembly by pulling to front while you are pulling up the tabs.

CN7 BACKUP

(ORANGE)

CHARGE

R61

Fig. 4

CIRCUIT DESCRIPTION

TKR- 750

1. Outline

The TKR-750 is a VHF/FM repeater designed to operate

in the frequency range of 136 to 174MHz.

The unit consists of receiver, transmitter, phase-locked

loop (PLL) frequency synthesizer, and control circuits.

2. Receiver Circuit

The receiver is double conversion super-heterodyne, designed to operate in the frequency range of 146MHz to 174MHz (K,E) or 136MHz to 150MHz (K2).

The receiver circuit located in TX-RX unit (X57-626 A/2) consists of the following : 2-1 front-end circuit, 2-2 first mixer, 2-3 IF amplifier circuit, 2-4 audio amplifier circuit, and 2-5 squelch circuit.

2-1. Front-end Circuit

The front-end circuit consists of BPF L2/L3, RF amplifier Q1, and BPF L5/L6/L7. The helical BPF covers frequency ranges 146 to 174MHz (K,E) and 136 to 150MHz (K2), with a passband of 3.0MHz.

TX-RX unit (X57 A/2): TX-RX

MCF (Wide)

XF2

MCF (Narrow)

XF1

44.850MHz

QUD

CF1 (Wide)

CF2 (Narrow)

455kHz

W/N

IF AMP Q2

SWSW

W/N

RSSI

DET

NOISE DET

SQL

IF AMP Q3

W/N

DET

W/N

FM SYSTEM IC IC9

NOISE AMP

The BPF L5/L6/L7 attenuates the unwanted signals, and

sends only the necessary signal to the first mixer DBM A1.

2-2. First Mixer

The signal from the BPF is heterodyned with the first local oscillator signal from the PLL frequency synthesizer circuit at the first mixer DBM (A1) to become a 44.85MHz first intermediate frequency (IF) signal. The first IF signal is fed through two monolithic crystal filters (XF2; Wide, XF1; Narrow) to further remove spurious signals.

2-3. IF Amplifier

The first IF signal is amplified by Q2 and Q3, and then enters IC9 (FM system IC). The signal is heterodyned again with a second local oscillator signal (44.395MHz) with in IC9 to become a 455kHz second IF signal. The second IF signal is fed through a 455kHz ceramic filter, CF1 (Wide), CF2 (Narrow) to further eliminate unwanted signal, and the quadrature detection circuit FM-detects the signal to produce a base-band signal and output it from pin 11.

44.85MHz

1st MIX

DBM A1

44.395MHz

LPF

BPF

L5,L6,L7

IF AMP Q9

RF AMP Q1

IF AMP Q8

fRX+44.85MHz

BPF

L2,L3

RX VCO A3 (X58-478)

VCO A

VCO B

RX ANT

TX-RX unit (X57 B/2): Control

DEI DEO

ASQ

RSSI

AMP

IC608

IC604

CPU

AINR

CODEC

IC614

AMP

IC619 (B/2)

AOUTR

LPF

IC619 (A/2)

Fig. 1 Receiver circuit

RXI RXO

SPM

IC615

DAC

IC621

IC622

INV

Q606

Q605

INT SP

MUTE

IC629

AMP

TKR- 750

CIRCUIT DESCRIPTION

2-4. Audio Amplifier

The audio amplifier circuit is located in control section of TX-RX unit (X57-626 B/2). The recovered audio signal obtained from IC9 is amplified by IC608, input to the AINR terminal of CODEC IC (IC614), and audio processed by DSP (IC618).

The processed audio signal from AOUTR terminal of IC614 is amplified by IC619 (B/2) to a sufficient level, antialiasing filtered by IC619 (A/2). The audio signal goes to an electronic volume (IC615) V3/V4, to the input of multiplexer IC (IC622), and is amplified to drive a loudspeaker by an audio power amplifier (IC629). The 4W audio output can be provided to external 4 ohms speaker through the 15-pin test connector “SPO, SPG” on the rear panel.

2-5. Squelch Circuit

The output signal from IC9 enters FM IC again, then passed through a band-pass filter.

The noise component output from IC9 is amplified by Q7 and rectified by D5 to produce a DC Voltage corresponding to the noise level. The DC voltage is sent to the analog port of the CPU (IC604).

IC9 outputs a DC voltage (RSSI) corresponding to the input of the IF amplifier.

3. Transmitter Circuit

The transmitter circuit consists of the following circuits : 3-1 microphone circuit, 3-2 modulation level adjustment circuit, 3-3 driver and final power amplifier circuit, and 3-4 automatic power control circuit.

3-1. Microphone Circuit

The signal from the microphone is passed through AGC circuit located in display unit (X54-333), so that it does not saturate. This circuit consists of IC501, D501, D502, Q501, and Q502. The AGC is operated by controlling the + and – side levels of amplitude using the current obtained by positive and negative detection of the amplified audio signal. The audio signal goes to control section of TX-RX unit (X57626 B/2) from display unit (X54-333).

The transmit audio signal goes to the input of the multiplexer IC (IC605) for microphone muting. The audio signal is amplified by IC610, input to the AINL terminal of CODEC IC (IC614), and audio processed by DSP (IC618). The processed audio signal from the AOUTL terminal of IC614 is amplified by IC616 (B/2) to a sufficient level, anti-aliasing filtered by IC616 (A/2), and amplified by the summing amplifier IC611 (A/2).

3-2. Modulation Level Adjustment Circuit

The output of the summing amplifier IC611 (A/2) is passed to an electronic volume (IC615) for maximum deviation adjustment before being applied to a varactor diode in the voltage controlled oscillator (VCO) A2 located in TX-RX unit (X57-626 A/2).

Display unit (X54 B/2)

MIC JACK

J601

TXRX unit (X57 B/2): CONTROL

MIC

MIS

TAS

Display unit (X54 A/2)

VR501

IC605 (A/2)

TXI TXO

IC501(A/2)

AMP

DET

IC610

AMP

Q501,502

D501,502

AINL

ATT

IC614

CODEC IC

Fig. 2 Microphone circuit

AOUTL

IC616

(B/2)

AMP

D-SUB

TDS

IC616

(A/2)

IC605 (B/2)

IC611

(A/2)

AMPLPF

IC615

DAC

FAG

FAB

CN4

OUT

VTH

FAS

IC2

TK11050M

IC7

BU4094BCF

CK, DT,

STB

CPU

IC604

TEMP

Q602

X45 A/2 X57 A/2 X57 B/2

FAN

OFF

+20°C +30°C +40°C +50°C

CIRCUIT DESCRIPTION

3-3. Driver and Final Power Amplifier Circuit

The transmit signal is generated by the TX VCO (A2), amplified by Q11, and sent to final unit (X45-362). This amplified signal is amplified by Q2, Q3, and Q4, and is passed to the FINAL stage. The RF power amplifier consists of MOS FET.

TKR- 750

TX-RX unit (X57-626 A/2)

STT

FCT

BUFF

IC1

TX VCO

(X58-479)

TCXO

16.8MHz

3-4. Automatic Power Control, Circuit and Transmitter

The automatic power control (APC) circuit stabilizes the transmitter output power at a pre-determined level, and consists of forward/reflected power detector circuits, and switching transistor Q8. The forward/reflected power detector circuits detects forward RF power and reflected RF power to DC voltage, and consists of a CM coupling type detection circuit formed by a strip line, RF detector D4/D5, and DC amplifier IC1 (A/2).

The voltage comparator (IC1 B/2) compares the above detected voltage with a reference voltage, set using the microprocessor and IC6 located in the TX-RX unit. An APC voltage proportional to the difference between the sensed voltage and the reference voltage appears at the output of IC1. This output voltage controls the gate voltage for the drive amplifier Q4 and final amplifier Q5, which keeps the transmitter output power constant.

3-5. Fan Action Control Circuit

If fan action is set to “Temperature”, the cooling fan is turned ON or OFF according to temperature.

If the ambient temperature of the final unit exceeds

approx. 40°C, the output from pin 6 of the temperature de-

tection IC2 changes from L to H. This signal is sent to the CPU (IC604) by Q602 in the TX-RX unit B/2 (control section), and the output from pin 13 (FAS) of IC7 in the TX-RX unit A/ 2 controlled by the CPU goes H.

This signal turns Q9 in the final unit ON to run the cooling

fan. It has a hysteresis of approx. 5°C by IC2. If fan action is

set to “Continuous”, the fan operates continuously, but Q9 stays ON.

Final unit (X45-362 A/2)

Q11

Q2 Drive AMP

ATT

Q3 Drive AMP

IC1

Q4 Drive AMP

AMP

REF

AMP

IC1

Fig. 3 Driver and final power amplifier circuit

[Fan operation]

Fig. 4 Fan action control circuit

Q5 Final AMP

Vcont

POWER ADJ

CM COUPLER

TEMP

D4 D5

REF

DET

VR1

TX ANT

FWD

DET

TKR- 750

Q351

VCO unit (X58-479)

STT

VCO A

IC300

VCO B

Q355

Q350

Q354

Q352

Q353

Q300

Q302

VCXO

TX-RX unit

IC604

AMP

AMPLPF

PLL-IC

µ-com

CP,DP EPT,LDT

MOMO

CIRCUIT DESCRIPTION

4. PLL Frequency Synthesizer

The PLL frequency synthesizer circuit consists of the fol-

lowing circuits : 4-1 receiver PLL circuit, 4-2 transmitter PLL circuit, and 4-3 unlocked detector circuit.

4-1. Receiver PLL

The receiver PLL circuit is located in VCO unit A3 (X58-

478) on TX-RX unit (X57-626 A/2), and consists of VCXO X2, VCO’s (Q350 and Q351), a single-chip PLL IC IC300, buffer amplifier Q355, and high-frequency amplifier Q302.

The VCXO generates 16.8MHz. The frequency stability is

within ±2.0ppm (Temperature range of –30 to +60°C). The

frequency tuning of the VCXO is done to apply a voltage to pin 1 of the VCXO. The output of the VCXO is applied to pin 8 of the PLL IC through the pin 7 of the VCO.

The first local oscillator is an upper heterodyne local oscil-

lator, and the VCO oscillator frequency is 180.850 to

218.850MHz. Two VCOs cover the two bands : Q350 covers the lower band and Q351 VCO covers the upper band.

The oscillator frequency is controlled by applying the

VCO control voltage, obtained from the phase comparator to the varactor diodes.

VCO unit (X58-478)

Q350

VCO A

Q355

AMP

TX-RX unit

4-2. Transmitter PLL

The transmitter PLL circuit is located in VCO unit A2 (X58-

479) on TX-RX unit (X57-626 A/2), and consists of VCXO X3, VCO’s (Q350 and Q351), a single-chip PLL IC IC300, buffer amplifier Q355, and high-frequency amplifier Q302.

The VCXO generates 16.8MHz. The frequency stability is

within ±2.0ppm (Temperature range of –30 to +60°C). The

frequency tuning and modulation of the VCXO are done to apply a voltage to pin 1 of the VCXO. The output of the VCXO is applied to pin 8 of the PLL IC through the pin 15 of the VCO.

The VCO oscillator frequency is 136.00 to 174.00MHz. Two VCOs cover the two bands : Q350 covers the lower band and Q351 VCO covers the upper band.

The oscillator frequency is controlled by applying the VCO control voltage, obtained from the phase comparator to the varactor diodes.

4-3. Unlock Detector Circuit

If a pulse signal appears at the LD pin of IC300, an unlock condition occurs, causing the voltage applied to the pin of the microprocessor to go low. The names of this pin are LDT for TX PLL and LDR for RX PLL. When the microprocessor detects this condition, the transmitter is disabled.

SRR

Q354

Q300

µ-com

VCO B

Q351

IC300

PLL-IC

IC604

Q352

Q353

CP,DP EPR,LDR

Q302

AMPLPF

VCXO

Fig. 5 Receiver PLL Fig. 6 Transmitter PLL

EEPROM

IC600

TX-RX unit (X57 B/2): CONTROL

IC601

Q600

X600

BEAT SHIFT

Reset IC

14.754 MHz

Q600

X601

BEAT SHIFT

16.515 MHz

FLASH ROM

CPU

IC609

IC620

232C DRIVER

IC615

D/A IC

IC602/623

Shift Register IC

INTERFACE IC

IC603/606

DSP

IC618

CODEC IC

IC614

DIVIDER

IC613

IC604

CIRCUIT DESCRIPTION

TKR- 750

5. Control Circuit

The control circuit mainly located in the control section of TX-RX unit (X57-626 B/2) consists of the following : 5-1 CPU, 5-2 memory circuit, 5-3 CPU clock shift, 5-4 shift register circuit, 5-5 display circuit, 5-6 DSP circuit, 5-7 base-band circuit, 5-8 RS-232C circuit, and 5-9 power supply circuit.

5-1. CPU

The CPU (IC604) is a 16bit single-chip microcomputer containing a 32k ROM and 3k RAM. This CPU controls the flash ROM, the DSP, the receiver circuit, the transmitter circuit, the control circuit, and the display circuit and transfers data to or from an external device.

5-2. Memory Circuit

IC609 has a flash ROM with a capacity of 2M bits that contains the control program for the CPU, the signal processing program for DSP and data such as channels and operating features.

This program can be easily written from an external device. Data such as the operating status are programmed into the EEPROM (IC600).

5-3. CPU Clock Shift

There are the 14.754MHz clock for the CPU (IC604) and the 16.515MHz clock for the DSP (IC618) at the control section of TX-RX unit (X57-626). When these clocks are multiplexed with the reception frequency, they become an internal beat signal. To prevent this, by tuning Q600 and Q604 on the clock frequency is shifted. (Shift on/off can be set through programming.)

5-5. Display Circuit

The display circuit (X54-333) contains two 7-segment LEDs D506, D507 (orange : see the operation manual for details of display), D503 (red : transmission), D504 (green : busy), two-color LED D505 (red : backup, green : main DC), LEDs in switches S501 to S506, IC502, IC503, IC504, and IC505 to display this model channels and states.

IC502 to IC505 are shift registers which convert serial data from the CPU to parallel data and light LEDs.

Q507, Q510, and Q511 are switching transistors which control two-color LED D505.

IC506, and IC507 are three-pin power supply ICs which produce power used for the display circuit.

5-4. Shift Register Circuit

Serial data is sent to the shift register (IC502 to IC505 located in display unit, IC602, IC623, IC7 located in TX-RX unit) from the CPU (IC604) to control various functions in the unit.

Display unit (X54-333-20 A/2)

BU4094BCFV

CLK,SOE, STB1

Shift Reg. 1

KEY LAMP

1~6

CLK,SOE, STB1

Shift Reg. 2

BU4094BCFV

CLK,SOE, STB1

Shift Reg. 3

BU4094BCFV

SWSW

Fig. 8 Display circuit

PF1~6

KEY1~5

CLK,SOE, STB1

SISISI

SOSOSO

Shift Reg. 4

BU4094BCFV

TX Main DC/

Fig. 7 Control circuit

DAT

SWSWSWSW

BUSY

BACKUP

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