TM-481A维修手册

SERVICE MANUAL This product complies with the RoHS directive for the European market. This product uses Lead Free solder. © 2011-12 PRINTED IN JA PAN B53-7001-00 (Y) 63 TM-481A 430MHz FM TRANSCEIVER Key top (K29-9497-01) Modular jack (MIC) (E58-0535-05) Panel assy (A62-1189-03) Knob (VOL) (K29-9498-03) Knob (ENC) (K29-9499-03) 4 DISASSEMBLY FOR REPAIR .....................2 CIRCUIT DESCRIPTION .............................5 COMPONENTS DESCRIPTION ..................9 SEMICONDUCTOR DATA .........................11 PARTS LIST ...............................................12 EXPLODED VIEW ......................................18 PACKING ...................................................19 ADJUSTMENT ...........................................20 TERMINAL FUNCTION .............................29 PC BOARD TX-RX UNIT (X57-8130-24) ....................30 SCHEMATIC DIAGRAM ............................36 BLOCK DIAGRAM .....................................40 LEVEL DIAGRAM ......................................42 SPECIFICATIONS ..................BACK COVER CONTENTS TM-481A 2 Document Copyrights Copyright 2011 by JVC KENWOOD Corporation. All rights reserved. No part of this manual may be reproduced, translated, distributed, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or other- wise, for any purpose without the prior written permission of JVC KENWOOD Corporation. Disclaimer While every precaution has been taken in the preparation of this manual, JVC KENWOOD Corporation assumes no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from the use of the informa- tion contained herein. JVC KENWOOD Corporation reserves the right to make changes to any products herein at any time for improvement purposes. 1. Disassembly Procedure 1. When removing the cabinet, fi rst remove the two screws from the right and left with a phillips screwdriver. Then, hook your fi nger on the edge of the cabinet and pull it out until it is over the chassis protrusion. Remove the cabinet by prying the cabinet as shown below. Cabinet DISASSEMBLY FOR REPAIR 2. To remove the panel assembly, fi rst turn the transceiver upside down. Then, insert a fl at-head screwdriver into the holes of the chassis and tilt it in the direction as shown by the arrow. Panel assembly Holes TM-481A 3 3. Disconnect the fl at cable from the connector of the panel assembly. Flat cable 4. To remove the Display PCB, fi rst remove the volume knob ① . Then, remove the encoder knob ② . Remove the two screws ③ from the Display PCB using a phillips screwdriver. Remove the speaker holder of the key top from the speak- er. ④ Remove the Display PCB with the speaker from the panel assembly. ⑤ Speaker holder of the key top Panel assembly Display PCB Ĭ ĭ Į Į į İ 5. When removing the TX-RX PCB, fi rst remove the solder of the antenna hot pin and positive terminal of the DC cord. Then, remove the 15 screws from the TX-RX PCB, power module, and audio amp. Positive terminal of the DC cord Antenna hot pin Power module TX-RX PCB Audio amp Note: When you supply power to the TX-RX PCB after removing the TX-RX PCB from the chassis, solder the positive and ground terminals of the DC cord (recommendation: E30- 3448-25) to the +B and GND terminals of the TX-RX PCB. TX-RX PCB Component side GND +B DISASSEMBLY FOR REPAIR TM-481A 4 6. Pull it out behind the chassis by rotating the bush ③ of the DC cord 90 degrees in the direction of the arrow after the screw ① in the negative terminal is removed, and the positive terminal ② is removed from the chassis. DC cord Ĭ ĭ Į 2. Precautions for Reassembly 1. Mount the key top and speaker onto the panel assembly. Then, tighten the two screws ① of the Display PCB. Insert the protrusion area of the key top into the groove area of the panel assembly using a fl at-head screwdriver. ② Then, mount the encoder knob ③ and volume knob ④ . Key top Panel assembly Display PCB Speaker Ĭ Ĭ ĭ Į į 2. When mounting the panel assembly, pass the fl at cable through the hole of the chassis as shown below, then con- nect the fl at cable to connector of the panel assembly. Hole of the chassis Panel assembly Panel assembly Chassis Chassis 3. Fit the panel assembly into the two tabs of the chassis top side fi rst. Then, fi t the panel assembly into the two tabs of the chas- sis bottom side by turning the panel assembly. Panel assembly Tabs 3. How to Mount the AF PA IC (IC715) Solder it onto the TX-RX unit (A/2) so that the AF PA IC part number label “LA4600” is on the reverse side. Pin 1 markerIC715 TX-RX UNIT (X57-8130-24) (A/2) : TX-RX section Component side DISASSEMBLY FOR REPAIR TM-481A 5 Frequency Confi guration The receiver utilizes double conversion. The first IF is 49.95MHz and the second IF is 450kHz. The fi rst local oscil- lator signal is supplied from the PLL circuit. The PLL circuit in the transmitter generates the necessary frequencies. Figure 1 shows the frequencies. ANT SW RF AMP 1st MIX AF PA TCXO MIC AMP x3 multiply RF AMP POWER AMP CF 450kHz MCF 49.95MHz IF SYSTEM PLL/VCO 16.8MHz 50.4MHz ANT RX TX SP MIC Fig. 1 Frequency confi guration Receiver System The receiver is a double conversion superheterodyne. The frequency confi guration is shown in Figure 1. ■ Front-end RF Amplifi er An incoming signal from the antenna is applied to an RF amplifier (Q505) after passing through a transmit/receive switch circuit (D309, D311, D306 and D307 are off), a notch fi lter (L707 and D715) and a band pass fi lter (L515, L514 and varactor diodes: D509, D508). After the signal is ampli- fi ed, the signal is fi ltered through a band pass fi lter (L512, L511, L510 and varactor diodes: D507, D506, D505) to elim- inate unwanted signals before it is passed to the fi rst mixer. The voltage of these diodes are controlled by tracking the MCU (IC707) center frequency of the band pass fi lter. (See Fig. 2.) ■ First Mixer The signal from the RF amplifi er is heterodyned with the fi rst local oscillator signal from the PLL frequency synthesiz- er circuit at the fi rst mixer (Q504) to create a 49.95MHz fi rst intermediate frequency (1st IF) signal. The fi rst IF signal is then fed through the monolithic crystal fi lter (MCF: XF501) to further remove spurious signals. ■ IF Amplifi er The fi rst IF signal is amplifi ed by Q503, and then goes to IC501 (FM processing IC). The signal is heterodyned again with a second local oscillator signal within IC501 to create a 450kHz second IF signal. The second IF signal is then fed through a 450kHz ceramic fi lter (Wide: CF501, Narrow: CF502) to further eliminate unwanted signals before it is am- plifi ed and FM detected in IC501. Item Rating Nominal center frequency 49.95MHz Pass bandwidth ±4.0kHz or more at 3dB 50dB stop bandwidth ±25.0kHz or less Ripple 1.0dB or less Insertion loss 5.0dB or less Guaranteed attenuation 80dB or more at fo ± 900kHz Spurious 50dB or more at fo ± 1MHz Terminating impedance 270 / 8.5pF Table 1 Crystal fi lter (L71-0655-05): XF501 Item Rating Nominal center frequency 450kHz 6dB bandwidth ±6.0kHz or more 50dB bandwidth ±12.5kHz or less Ripple 2.0dB or less Insertion loss 6.0dB or less Guaranteed attenuation 35.0dB or more within fo ± 100kHz I/O matching impedance 2.0k Table 2 Ceramic fi lter (L72-0993-05): CF501 Item Rating Nominal center frequency 450kHz 6dB bandwidth ±4.5kHz or more 50dB bandwidth ±10.0kHz or less Ripple 2.0dB or less Insertion loss 6.0dB or less Guaranteed attenuation 60.0dB or more within fo ± 100kHz I/O matching impedance 2.0k Table 3 Ceramic fi lter (L72-0999-05): CF502 ANT L515,L514 D509,D508 BPF Q505 RF AMP Q503 IF AMP IC705 D/A CONVERTER Q504 MIX XF501 MCF D306,D307 D309,D311 ANT SW IC705 D/A IC706 DC AMP Q501 x3 multiply X1 TCXO IC501 FM IC 1st local OSC (VCO/PLL) W/NO (EVOL2) CF501 (Wide) CF502 (Narrow) TV MCU L511,L510 D506,D505 BPF L707,D715 NOTCH FILTER Fig. 2 Receiver system CIRCUIT DESCRIPTION TM-481A 6 ■ Wide/Narrow Switching Circuit The Wide port (pin 65) and Narrow port (pin 64) of the MCU is used to switch between ceramic fi lters. When the Wide port is high, the ceramic fi lter SW diodes (D501, D502) cause CF501 to turn on to receive a Wide signal. When the Narrow port is high, the ceramic fi lter SW di- odes (D501, D502) cause CF502 to turn on to receive a Narrow signal. (See Fig. 3.) Narrow IC707 64pin IF_IN MIX_O IC501 FM IC CF502 (Narrow) CF501 (Wide) R 50 5 R 50 7 R506 R504 D501 D502 Wide IC707 65pin Fig. 3 Wide/Narrow switching circuit ■ AF Signal System The detection signal from the FM IC (IC501) goes to the D/A converter (IC705) to adjust the gain and is output to the AF fi lter (IC709) for characterizing the signal. The AF signal output from IC709 and the DTMF signal, BEEP signal are summed and the resulting signal goes to the D/A converter (IC705). The AFO output level is adjusted by the D/A con- verter. The signal output from the D/A converter is input to the audio power amplifi er (IC715). The AF signal from IC715 switches between the internal speaker and the speaker jack (J701) output. (See Fig. 4.) AF Filter D/A CONV. D/A CONV. IC705 IC709 IC705W/NO (EVOL2) AF PA IC715 SP FM IC IC501 Fig. 4 AF signal system ■ Squelch Circuit The detection output from the FM IC (IC501) passes through a noise amplifier (Q502) to detect noise. A volt- age is applied to the MCU (IC707). The MCU controls the squelch according to the voltage (SQIN) level. The signal from the RSSI pin of IC501 is used for the S-meter. The electric fi eld strength of the receive signal can be known be- fore the SQIN voltage is input to the MCU, and the scan stop speed is improved. Q502 NOISE AMP D503IC501 IC707 FILOUT RSSI DET MCUFM IC SQIN RSSI Fig. 5 Squelch circuit PLL Frequency Synthesizer The PLL circuit generates the fi rst local oscillator signal for reception and the RF signal for transmission. ■ PLL The frequency step of the PLL circuit is 5 or 6.25kHz. A 16.8MHz reference oscillator signal is divided at IC1 by a fi xed counter to produce the 5 or 6.25kHz reference frequen- cy. The voltage controlled oscillator (VCO) output signal is buffer amplifi ed by Q9, then divided in IC1 by a dual-module programmable counter. The divided signal is compared in phase with the 5 or 6.25kHz reference signal in the phase comparator in IC1. The output signal from the phase com- parator is fi ltered through a low-pass fi lter and passed to the VCO to control the oscillator frequency. (See Fig. 6.) ■ VCO The operating frequency is generated by Q6 in transmit mode and Q4 in receive mode. The oscillator frequency is controlled by applying the VCO control voltage, obtained from the phase comparator, to the varactor diodes (D4 and D6 in transmit mode and D3 and D5 in receive mode). The TX/RX pin is set high in receive mode causing Q7 and Q5 to turn Q6 off, and turn Q4 on. The TX/RX pin is set low in transmit mode. The outputs from Q4 and Q6 are amplifi ed by Q9 and sent to the RF amplifi ers. (See Fig. 6.) D4,D6 Q6 TX VCO Q9 BUFF AMP D3,D5 Q4 RX VCO Q5,Q7 T/R SW Charge pump LPF Phase comparator 1/M 1/N 5kHz/6.25kHz 5kHz/6.25kHz REF OSC 16.8MHz PLL DATA IC1 : PLL IC Q3 AMP RF amplifiers Q1,Q2 TX/RX (MCU) Fig. 6 PLL circuit CIRCUIT DESCRIPTION TM-481A 7 ■ Unlock Circuit During reception, the 8RC signal goes high, the 8TC signal goes low, and Q708 turns on. Q710 turns on and a voltage is applied to 8R. During transmission, the 8RC sig- nal goes low, the 8TC signal goes high and Q709 turns on. Q711 turns on and a voltage is applied to 8T. The MCU monitors the PLL IC (IC1) LD signal directly. When the PLL is unlocked during transmission, the PLL LD signal goes low. The MCU detects this signal and makes the 8TC signal low. When the 8TC signal goes low, no voltage is applied to 8T, and no signal is transmitted. (See Fig. 7.) IC707 MCU Q708 SW Q710 SW IC1 PLL Q709 SW Q711 SW LD 8RC 8C 8R 8T 8TC PLL lock : LD “H” Fig. 7 Unlock circuit Transmitter System ■ Outline The transmitter circuit produces and amplifi es the desired frequency directly. It FM-modulates the carrier signal by means of a varicap diode. ■ Power Amplifi er Circuit The transmit output signal from the VCO passes through the transmission/reception selection diode (D9, D10) and is amplifi ed by Q303. The amplifi ed signal goes to the power module (IC302) through a low-pass fi lter. The low-pass fi lter removes unwanted high-frequency harmonic components, and the resulting signal is transmitted through the antenna terminal. (See Fig. 8.) ■ APC Circuit The automatic transmission power control (APC) circuit detects part of a fi nal amplifi er output with a diode (D313, D314) and applies a voltage to IC303. IC303 compares the APC control voltage (PC) generated by the D/A converter (IC705) and DC amplifi er (IC706) with the detection output voltage. IC303 generates the voltage to control the Vgg of IC302 and stabilizes the transmission output. The APC circuit is configured to protect over current of IC302 due to fl uctuations of the load at the antenna end and to stabilize transmission output at voltage and temperature variations. (See Fig. 9.) Fig. 8 Transmitter system Fig. 9 APC circuit Q10 RF AMP Q303 ANT DRIVE AMP IC302 POWER MODULE IC705 Q6 D/A CONVERTER D/A CONVERTER X1 TCXO 16.8MHz VCO IC1 PLL Q9 BUFFER Q3 RF AMP IC706 BUFFER IC101 IC705 MIC KEY INPUT MCU IC706 SUM AMP IC704IC703MIC MIC/IDC SPLATTERFILTER DRIVE AMP Q303 POWER MODULE IC302 DC AMP IC706 ANT SW D306,D307 D309,D311 LPF ANT POWER DET D313,D314IC303 APC CONTROL D9 IC705 (PC/TVO) (PC) CIRCUIT DESCRIPTION TM-481A 8 Control Circuit The MCU carries out the following tasks (See Fig. 10.): 1) Controls the WIDE, NARROW, and TX/RX outputs. 2) Controls the display circuit. 3) Controls the PLL IC (IC1). 4) Controls the D/A converter (IC705) and adjusts the vol- ume, modulation and transmission power. IC705 D/A converter IC1 PLL IC707 MCU EVLLD DT CK PLLE Fig. 10 Control circuit ■ Memory Circuit The transceiver has an 64k-bit EEPROM (IC708). The EEPROM contains adjustment data. The MCU (IC707) con- trols the EEPROM through three serial data lines. (See Fig. 11.) EEPCK IC707 MCU IC708 EEPROM EEPSDT EEPWP Fig. 11 Memory circuit ■ Display Circuit The MCU (IC707) controls the display LCD and LEDs. When power is on, the LCD driver will use the BL line to control the LCD illumination and key backlight LEDs. The brightness function is controlled by switch Q904. The LCD driver (IC901) and MCU (IC707) communicate through the CE, CL, DI, and DO lines. (See Fig. 12.) Q901 SW Q902 SW IC707 MCU D903~D905 Q903 SW D906~D911 Q904 SW IC901 LCD driver CE CL DO DI BL COM0~ COM3 SEG0~ SEG30 LCD BRI Fig. 12 Display circuit ■ Key Matrix Circuit The front panel has function keys. Each of them is con- nected to a cross point of a matrix of the KI1 to KI3 and KSI to KS2 ports of the LCD driver. The LCD driver monitors the status of the KI1 to KI3 and KS1 to KS2 ports. If the state of one of the ports changes, the LCD driver assumes that the key at the matrix point cor- responding to that port has been pressed. IC901 LCD driver KI1 KI2 KI3 KS2 KS1 FUNC REV CALL VFO MR MHz (Encoder) Fig. 13 Key matrix circuit ■ Encode The CTCSS and DCS signals are output from TONE of the MCU (IC707). The DTMF signal is output from DTMF of the MCU (IC707). These signals are summed with a MIC signal by the summing amplifi er (IC706), and the resulting signal goes to the D/A converter (IC705) to adjust the MOD level, and then goes to the buffer amplifi er (IC706). Part of the signal goes to the TCXO, and the rest goes to the D/A converter (IC705) in order to adjust the modulation balance between the VCO and TCXO. X1 TCXO VCO IC706 SUM AMP IC705 D/A IC705 D/A IC706 BUFFER IC1 PLL Amp MICIC707 MCU TONE DTMF Fig. 14 Encode ■ Decode • CTCSS/DCS The signal (W/NO (EVOL2)) goes to DTMF IN (pin 95) of the MCU (IC707) through the amplifi er (IC709). The CTC- SS/DCS signal will pass through the low-pass fi lters in the MCU (IC707) and be decoded within the MCU (IC707). IC707 MCU IC709 AMPDTMF IN W/NO (EVOL2) 95 Fig. 15 Decode CIRCUIT DESCRIPTION TM-481A 9 ■ D/A Converter The D/A converter (IC705) is used to adjust the MO mod- ulation, AF volume, TV voltage, FC reference voltage, and PC POWER CONTROL voltage level. Adjustment values are sent from the MCU as serial data. The D/A converter has a resolution of 256 and the following relationship is valid: D/A output = (Vin – VDAref) / 256 x n + VDAref Vin: Analog input VDAref: D/A reference voltage (Approx. 2.2V) n: Serial data value from the microprocessor (MCU) Power Supply Circuit When the power switch on the display unit is pressed, the power port on the display unit which is connected to port 17 (POWER), goes low, then port 82 (SBC) goes high, Q713 turns on, SB SW (Q714) turns on and power (SB) is sup- plied to the radio. When the DC power is supplied to the radio, the voltage regulator IC (IC713) is supplied to the MCU VDD and re- set voltage detect IC (IC714). IC714 will generate a signal (RESET) into the reset terminal of the MCU (IC707) to carry out a power ON reset. If DC power is less than approxi- mately 9.5V, the radio is unable to power on. When the DC power voltage deceases from the normal voltage, the INT voltage detector IC (IC712) will set to high on MCU port 18 (INT) if B line becomes less than approxi- mately 9.5V. The MCU will then send the backup data to the EEPROM (IC708) and enter stop mode. This circuit has an overvoltage protection circuit. If a DC voltage of 18V or higher is applied to the base of Q707, this voltage turns Q707 on and will set to high on MCU port 18 (INT). The MCU will then send the backup data to the EE- PROM (IC708) and enter stop mode. (See Fig. 16.) Q714 SW Q713 SW Q707SW IC713 AVR D712D710 B IC714 RST SBC R 82 4 R 82 5 IN T 5M IC707 MCU POWER SW POWER R ES ET 5M IC712 INT SB Fig. 16 Power supply circuit CIRCUIT DESCRIPTION TX-RX UNIT (X57-8130-24) Ref. No. Use / Function Operation / Condition / Compatibility IC1 PLL IC Frequency control IC302 Power module TX fi nal amplifi er IC303 APC controller TX power control IC501 FM IC FM detector/ 2nd mixer/ RSSI/ Noise amplifi er IC703 OP amplifi er MIC amplifi er/ IDC IC704 OP amplifi er Splatter fi lter IC705 Digital potentiometer Frequency adjustment Modulation balance adjustment AF level adjustment Backlight control Modulation limit adjustment TX power/ BPF control RX signal level control Ref. No. Use / Function Operation / Condition / Compatibility IC706 OP amplifi er Buffer amplifi er/ SUM amplifi er/ DC amplifi er/ 1/2 VCC IC707 MCU IC708 EEPROM Tuning data/ Memory data IC709 OP amplifi er Audio fi lter IC710 5V AVR 5C IC711 8V AVR 8C IC712 Voltage detection MCU INT voltage detection IC713 5V AVR 5M IC714 Voltage detection MCU reset voltage detection IC715 Audio amplifi er Audio fi nal amplifi er IC901 LCD driver Display control Q1,2 Switching Charge pump Q3 RF amplifi er PLL Fin COMPONENTS DESCRIPTION TM-481A 10 Ref. No. Use / Function Operation / Condition / Compatibility Q4 Oscillator RX VCO Q5 T/R switch On when RX Q6 Oscillator TX VCO Q7 T/R switch Q8 Ripple fi lter Q9 Buffer amplifi er Output of VCO Q10 RF amplifi er Output of VCO Q303 Drive amplifi er TX driver Q501 Tripler 16.8MHz × 3 Q502 SQL amplifi er Noise amplifi er Q503 IF amplifi er Q504 Mixer 1st mixer Q505 RF amplifi er LNA Q506 PC/TV switch On when TX Q701 AGC/ MIC m