Kenwood_UBZ-LJ8_serv.pdf

2002-12 PRINTED IN JAPAN B51-8644-00 (N) 506 FM TRANSCEIVER UBZ-LJ8 SERVICE MANUAL CIRCUIT DESCRIPTION . 2 COMPONENTS DESCRIPTION . 7 TERMINAL FUNCTION. 7 SEMICONDUCTOR DATA . 8 PARTS LIST. 9 EXPLODED VIEW. 13 PACKING . 14 ADJUSTMENT . 15 PC BOARD TX-RX UNIT (X57-6672-70) (A/2). 20 TX-RX UNIT (X57-6672-70) (B/2) . 24 SCHEMATIC DIAGRAM. 26 BLOCK DIAGRAM. 30 LEVEL DIAGRAM. 32 UBC-4 (BATTERY CHARGER) . 33 UPB-1 (BATTERY PACK) . 33 SPECIFICATIONS. BACK COVERB : Black Y : Yellow SL: Silver CONTENTS Antenna (T90-1016-05) Knob (VOL) (K29-9258-03) Button knob (PTT) (K29-9257-03) Cap (SP/MIC) (B09-0673-03) Front glass (B10-2742-03) : B (B10-2748-03) : SL,Y Key top (4 keys) (K29-9256-02) Cabinet assy (Front) (A02-3794-03) : B (A02-3795-03) : Y (A02-3796-03) : SL UBZ-LJ8 2 Frequency Configuration CIRCUIT DESCRIPTION Receiver System Front End The high-frequency signal received from antenna passes through a LPF (Low pass filter : components between ANT and C73) to filter out unwanted high frequency signal. A switch diode system (D8, L32 and D10) allows this signal to pass through and enters the BPF (Band pass filter : L31) to eliminate unwanted signal when receiving. The resulting signal is amplified by high-frequency ampli- fier (Q9) and goes to the first mixer (Q10). First Mixer The amplified signal that reaches Q10 is mixed with the first local signal from a VCO to produce a first IF signal (21.7MHz). (Receive frequency First local frequency = First IF frequency = 21.7MHz) The first IF signal passes through MCF (Monolithic crystal filter) XF1 to eliminate unwanted components. The first IF signal is amplified by IF amplifier (Q11) before going into FM IC (IC2). BPF 446MHz MIX, IF DET AF AMP MIC AMP RF AMP RF AMP RF AMP PLL VCO 1st MIX 21.7MHz MCF 21.25MHz 21.25MHz SP MIC TCXO Simplex 446.00625 446.09375MHz Simplex 424.30625 424.39375MHz LPF RF AMP ANT Simplex 446.00625446.09375MHz ANT SW Fig. 1Frequency configuration Reception methodDouble super heterodyne 1st IF frequency21.7MHz (Lower) 2nd IF frequency450kHz (Lower) Transmission methodVCO direct amplification ModulationVariable reactance phase modulation Table 1 MIX, DET SP ANT ANT SW D8,D10 L32 RF AMP Q9 IF AMP Q11 AF AMP IC203 1st MIX Q10LPF MCF XF1 21.7MHz FM IC IC2 BPF L31 446MHz 1st local OSC (PLL)2nd local OSC Fig. 3Receiver front end and Mixer circuit Fig. 2Receiver section configuration VCO 1st local OSC Q10 XF1 Q11 3R3R FM IC L32 LPF D8 3TANT D10 Q9 3R L31 ItemRating Nominal center frequency (fo)21.7MHz Pass bandwidth3.75kHz or more at 3dB Attenuation bandwidth14kHz or less at 40dB Ripple1dB or less Insertion loss3.5dB or less Ultimate attenuation80dB or more (fo 910kHz) Spurious responses40dB or more (fo 1MHz) Terminating impedance8505% / 5pF0.5pF Table 2MCF (L71-0616-05) : TX-RX Unit XF1 ItemRating Nominal center frequency (fo)450kHz 6dB bandwidth4.5kHz or more 50dB bandwidth10kHz or less Ripple (450kHz 3kHz)3dB or less Guaranteed attenuation (100kHz)40dB or more Insertion loss4dB or less I/O matching impedance2.0k10% Table 3Ceramic filter (L72-0974-05) : TX-RX Unit CF1 UBZ-LJ8 3 IF Amplifier The IF circuit consists of FM IC (IC2). This IC contains local line input buffer, Mixer, FM DET and audio frequency amplifier. The First IF signal that comes from IF amplifier (Q11) then goes into the FM IC mixer. It is mixed with second local fre- quency (21.25MHz) that comes from the PLL IC reference oscillation crystal so as to produce a second IF signal. (21.7MHz 21.25MHz = 2nd IF = 450kHz) The 2nd IF signal then enters to ceramic filter (CF1) in or- der to eliminate unwanted components. The filtered signal is amplified by a limiter-amplifier, which consists of 6 differen- tial amplifiers, to eliminate AM signal from 2nd IF. The FM detector acts as a quadrature discriminator. The phase of the output signal from the limiter is shifted by 90 degrees by a quad coil (L36). This output signal is compared with the original non-shifted waveform to produce FM detec- tion output. Squelch Circuit A squelch circuit is provided to prevent interference from noise or weak signal being output to the speaker during non- transmitting state. This circuit contains an amplifier (Q13) and a rectifier (D11). The amplifier amplifies noise signals from FM detec- tion output and passes them to a rectifier. When there is no signal or weak signal being received, the FM IC detection will output high frequency noise and the rec- tifier will output high voltage level. When strong signal is received, the FM IC detection noise is suppressed and the rectifier output voltage level will be low. MPU compares this rectifier output level to a predeter- mined level so as to determine when to turn on the speaker. Noise amplifier (Q13) and rectifier (D11) are used here in- stead of FM IC internal circuit to prevent temperature toler- ance. IC2 FM IC RSSI 161514131211109 12345678 LPF MIX Buff QUAD DET INV Noise AMP IF AMP OSC IC203 AF AMP CF1 450kHz 2nd local OSC 21.25MHz PLL IC L36 Quad coil 3R3RAF OUT AF IN SP Q216 Q220 Batt 10 SP AMP 1 BUSY D11 Q13 2 RSSI IC208 MPU 1st IF input (21.7MHz) AF Amplifier The FM detection output signal passes through the base band IC (IC209) which consists of band pass filter (300Hz3kHz), de-emphasis circuit and amplifier. Next, the signal is passed to the volume control potential meter VR201 and then goes into the audio power amplifier (IC203) which drives the speaker to produce audio output. Loudness ON/OFF Circuit Loud On/Off switching circuit is controlled by AF switch (Q217,Q219,Q218). When Loud on, Q217 is On Q218 is Off. When Loud off, Q217 is off Q218 is on. When the SP/MIC option is inserted, Loud circuit be- comes Off automatically. Fig. 4IF amplifier and Squelch circuit Fig. 5AF amplifier and Loudness on/off circuit SP C206 + Q217 Q219 Q218 IC203 AF AMP VR201 AMP AMP 2320 De-emphasis BPF AFOUT IC209 : Base band IC BTL SP AMP SP MUT RXINRXAF CIRCUIT DESCRIPTION UBZ-LJ8 4 Transmitter System Microphone Amplifier Circuit The audio signal acquired from the microphone (MIC200) passes through the MIC amplifier (IC204) to perform signal amplification. An AGC (Automatic gain control) circuit is in- cluded to maintain output audio signal level. The amplified signal passes through the amplifier, pre- emphasis circuit, limiter and Splatter filter contained inside base band IC (IC209) and reaches the VCO as modulation sig- nal. The splatter filter will eliminate the distortion compo- nents outside the audio band. Modulation Circuit The output signal of the base band IC passes through VR1 for Max Deviation Adjustment and goes to the modulation input of the VCO circuit for a variable reactance phase modu- lation. VOX Circuit After amplified by MIC amplifier (IC204), MIC signal passes through VOX amplifier (Q201) to eliminate signal which is out of frequency range 300Hz2.5kHz. The resulting signal goes into rectifier (D203) and converts into DC level. This DC level is compared with preset value in MPU. If the level is higher than preset, MPU will start trans- mitting. Transmission Output Circuit The VCO output is amplified by a high-frequency amplifier circuit (Q14, Q7 and Q8). The resulting signal will pass through a high-frequency antenna switch (D8), a low pass fil- ter before being transmitted by the antenna. The output power is about 500mW with 4.5V DC supply at battery terminal. Low Pass Filter Circuit A three-stage low-pass filter is located between the an- tenna and the antenna switch circuit. It helps to remove the harmonic components that is generated by transmission cir- cuit. Fig. 6Transmitter section configuration Fig. 7Microphone amplifier circuit Fig. 9Transmission output circuit Fig. 8VOX circuit MIC IC204 MIC AMP VR1 Q2,Q4,Q6 VCO Q14 RF AMP Q7 RF AMP Q8 RF AMP ANT SWLPF ANT AMP Pre- emphasis BPFAMP Limiter Splatter filter 3 TX IN 7 MOD VCO IC209 : Base band IC IC204 MIC AMPMIC Q200 AGC MIC IC204 MIC AMP Q201 VOX AMP 4 VOX IC208 MPU D203 VCO Q14 Q7Q8 VR4 3T3T3TB D8 D10 LPF ANT PLL System VCO Circuit The VCO circuit is housed in a shielding case. The VCO circuit consists of a oscillation transistor (Q2), a variable capacitor diode (D2) for frequency control, a variable capacitor diode (D3) for variable reactance modulation, trans- mit/receive frequency switch diode (D1), control switch (Q1), ripple filter (Q3) and buffer amplifier (Q4). The oscillation frequency is mainly determined by C12, C13, D2 and L3 (TX) or L3 and L2 (RX). D3 is used for modu- lation. In RX mode, the TX/RX switch line goes low; switch Q1 and D1 turn off. The inductor L2 will be connected to oscilla- tion circuit and Q2 will produce the first local frequency for reception purpose. (Receiving channel frequency subtracted by 21.7MHz equals to the receive frequency.) In TX mode, the TX/RX switch line goes high; switch Q1 and D1 turn on. The inductor L2 is bypassed to ground through C2, D1 and C3. Q2 oscillation frequency becomes about 446MHz and the VCO will output the frequency which is needed for transmission. The ripple filter (Q3) produces a 2.4V voltage supply for the oscillation transistor (Q2). D4 is used for speeding up the ripple filter operation when 3C line turns on. CIRCUIT DESCRIPTION UBZ-LJ8 5 PLL Circuit Frequency data is sent to the PLL IC (IC1) from MPU (IC208) through common data line either when the set is powered on, or when channel is changed, or when transmit is required. This data sets the dividers and CP (Charge Pump) of PLL IC. The TCXO (X1) produces a 21.25MHz reference frequency and passes to PLL IC. Reference frequency is divided to pro- duce a 12.5kHz for comparison of frequency inside PLL IC. The VCO output frequency is also passed to the PLL IC via Fin. The divider of the PLL IC, which is set by MPU, also di- vides this frequency. These two frequencies will be com- pared by the phase comparator circuit of PLL IC so as to de- tect the phase difference. From the phase detection results, charge pump will be able to output the PWM (Pulse Width Modulation) pulse. This output voltage will then be used to control the VCO fre- quency through PLL Loop Filter. This control voltage passes through the loop filter which is applied at the VCO control pin to control the oscillation fre- quency. Basically, the loop filter removes unwanted harmon- ics and noise produced at the output of the charge pump. It also determines the PLL response by synchronizing the am- plitude and phase characteristics. Unlock Detection Circuit If the PLL cannot synchronize for some reason during op- eration, the PLL IC will output a low voltage level signal at LD (pin 5) to the MPU. MPU will stop transmitting or receiving to prevent wrong frequency transmitted or received. Control System Reset Circuit When a battery is inserted, the MPU power supply pro- vides the operating voltage after about 0.5sec. The reset IC (IC202) output a low signal to reset the MPU so that MPU starts to work correctly. When battery voltage is lower than 3.0V (set working volt- age limits) or battery is removed, another reset IC (IC206) will send a reset to MPU so as to prevent this unit from working under non-guarantee low voltage condition. Battery Voltage Indication Circuit The unit contains a battery voltage detection circuit. This circuit monitors battery voltage every half second and dis- plays bars on LCD to indicate the battery level. Once battery voltage drops below 3.2V, indicator will start flashing on LCD and TX operation inhibits. R11R12 R15 C10 C16 C22 C13 L6 R10 R7 R4 R2 R8 R13 R14L4 L2 C9 C8 C19 C5 C6 R6 C3 C7D3 D2 D1 D4 C12 C15C26 R16 C4 C2 L3L1Q2 Q4 Q3 + L5R17 R9 LV R3 R5 Q1 TX/RX3CMOD VCO output L9 3 1 + + + Loop filter CP1Xin 11 TCXO X1 Vcon 3C 3C 554 LD IC208 MPU Fin1 VCO LV (Lock Voltage) 3C,T/R,MOD VCO out STB DATA CK PLL DATA (MPU) IC1 PLL IC UL Fig. 10VCO circuit Fig. 11PLL circuit Fig. 12Reset, battery voltage indication and Power supply circuit IC202 IC207 IC206 47 4863 49 46 60814 VCCRESETBATTL 3TC 3RC 3MC SAVE BATT IC208 MPU B3M VR4 PA Q211 Q215 Q212 Q210 3MS 3C 3R 3T CIRCUIT DESCRIPTION UBZ-LJ8 6 Power Supply Circuit The battery voltage directly supplies RF final amplifier (Q8) and AF amplifier (IC203) through AVR (Q216). IC207 supplies 3V voltage to MPU, EEPROM and power key. Switch Q211 delivers 3V supply 3MS to base band IC, MIC amplifier and VOX circuit when necessary. Switch Q215 delivers 3V supply 3C to VCO and PLL circuit during receiving, transmitting or standby. Switch Q212 delivers 3V supply 3R to FM IC, Mixer, RX amplifier and IF amplifier during receiving or standby. Switch Q210 delivers 3V supply 3T to TX amplifier Q14, Q7, TX/RX switch and the power control circuit of Q8. Fig. 13Speaker, microphone jack and Remote control circuit 3.9KSW1 LOCK SW PTT 10KSW2 27KSW3 Internal MIC PTT 3MS MIC SP/MIC DET AFO R295 IC208 MPU REM 3 2.5 3.5 External MIC External SP (SMC-34 remote control speaker microphone) IC203 AF AMP 3R AF IN SP Q216 Q220 Batt 10 SP AMP 1 BUSY D11 Q13 2 RSSI IC208 MPU 64 57 CTCSS IN CTCSS OUT FILOUT RSSI 7 12 IC2 FM IC AFOUT 9 IC211 LPF 15 21 7 IC209 Base band IC 23 VCO TX AMP Mixer RX AMP R273 C267 C266 R272 RC LPF Fig. 14CTCSS circuit If there is no incoming signal or key press after 5 second, unit will enter its power save mode. In power save mode, 3C and 3R will be turned on and off respectively for power sav- ing. Remote Control Circuit The voltage at the MPU REM (pin 3) will be converted into a digital signal to carry out remote operation according to the predetermined voltages level. The REM pin is set to about 3V by pull up resistor. When remote control switch is pressed, the voltage divided by the resistor in series with the pull up resistor will generate a volt- age for MPU to recognize the operation. CTCSS Circuit The tone frequency is generated by MPU (pin 57). This PWM signal becomes a sinusoidal waveform after passing through a RC low pass network. It will mix with voice signal from base band IC and becomes modulation signal for VCO. During receiving, the QT signal received from FM IC will go through the base band IC so that signal with less than 300Hz will be output via IC209 pin 21. Next, it will pass through the low pass filter (IC211) so as to eliminate un- wanted noise. Then the filtered tone will be passed to the pin 64 of MPU where the digital filter inside the MPU will detect the tone. If the tone is matched, MPU will turn on the speaker. CIRCUIT DESCRIPTION UBZ-LJ8 7 TX-RX Unit (X57-6672-70) (A/2) : Control Ref. No.Use/FunctionOperation/Condition/Compatibility Q200MIC Mute SwitchOn when microphone mute Q201VOX A