Motorola Lcs2000 68p02945c70 O Manual
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5-4 Disassembly & Reassembly Assemble the Radio Assemble the Control Head1. Insert the LCD frame with LCD and Zebra connectors into its place. 2. Place the keypad onto the board assembly, making sure the keypad is ßush with the board. 3. Rotate the potentiometer counterclockwise. Rotate the volume knob counterclockwise. This will allow you to insert the potentiometer smoothly into its place in the volume knob. 4. Make sure the speaker including the gasket is well positioned. 5. Connect the printed circuit board to the speaker. 6. During the installation of the printed circuit board, ensure the four protruding tabs snap into the recesses. Replace the Main Board1. Inspect and if necessary, reapply thermal grease to the heatsink- ing pads in the chassis. 2. Install the 8 screws with 0.4 -07 NM (4-6 in lbs) of torque using a T8 TORX driver. 3. Before installing the connector retaining clips, ensure that the board is sitting ßush on the chassis mounting surface. 4. Install the PA shield and secure it with 3 screws. Replace the Top Cover and Control Head1. Position the top cover over the chassis and replace. Ensure that the crosses snap into the recesses. 2. Connect the control head to the radio by the ßex. 3. Press the control head onto the radio chassis until the protruding taps on the chassis snap into the recesses inside the control housing.
Radio Tuning Procedure 6-1 6Radio Tuning Procedure6 Radio Tuning Procedure GeneralAn IBM PC (personal computer) and RSS (Radio Service Software) are required to align the radio. Refer to the applicable RSS Manual for installation and setup procedures for the software. To perform the alignment procedures, the radio must be connected to the PC, RIB (Radio Interface Box), and Test Set as shown in Figure 6-6. Figure 6-6 Radio Alignment Test Setup BNC RIB RIB POWER SUPPLYCOMPUTER INTERFACE CABLEDATA GNDCOMPUTER AUDIO GENERATOR SINAD METER AC VOLTMETER TX RX 30 dB PAD 30 dB PAD RF GENERATORSERVICE MONITOR WATTMETER TRANSMIT RECEIVE TEST SETRADIO PROGRAM or AUDIO IN SMA-BNC TEST CABLE 15-PIN 25-PINNote: Battery can be used in RIB MIC INor COUNTER 0180357A57, 110 V, USARLN4008B 30-80369B72 (IBM AT, 9-PIN ONLY) 30-80369B71 (IBM XT, 25-PIN ONLY) making power supply optional. 58-80348B33 TEST CABLE 3080070N01RLN4460A 3008566C12 0180358A56, 110 V, USA
6-2 Radio Tuning ProcedureFigure 6-7 Service Menu Structure All SERVICE screens read and program the radio codeplug directly; you do NOT have to use the RSS GET/SAVE functions to program new tuning values. The SERVICE screens use the concept of the ÒSoftpotÓ, an analog SOFTware controlled POTentiometer used for adjusting all transceiver alignment controls. Each SERVICE screen provides the capability to increase or decrease the ÔsoftpotÕ value with the keyboard UP/DOWN arrow keys respectively. A graphical scale is displayed indicating the minimum, maximum, and proposed value of the softpot, as shown in Figure 6-8. Figure 6-8 Softpot Concept CAUTION Do NOT switch radios in the middle of any SERVICE procedure. Always use the EXIT key to return to the MAIN menu screen before disconnecting the radio. Improper exits from the SERVICE screens may leave the radio in an improperly conÞgured state and result in seriously degraded radio or system performance. F6 F2 Alignment MenuBoard Replacement Menu Service Menu F2 Logic or RF Board Replacement F3 Tx Power F4 Warp Reference Frequency F5 Tx Power Calibration F6 Tx Deviation Calibration F3 Deviation Adjustment F5 Reference Oscillator Warp F7 Transmitter Power F8 Squelch Adjustment F9 Squelch Adjustment ! MAEPF-22858-O Min. ValueMax. Value 0 15
Radio Tuning Procedure 6-3 Tuning Procedure Starting the Tuning Procedure1. From the SERVICE menu, press F6 to select BOARD REPLACEMENT. 2. Press F2 for LOGIC OR RF BOARD replacement. Note:Perform the following procedures in the sequence indicated. Reference Crystal Data1. Press F2 to select REFERENCE CRYSTAL DATA. 2. Press F8 for PROGRAM VALUE. Tx Power1. Press F3 to select Tx POWER. 2. Press F6 to key the radio. The screen will indicate that the radio is transmitting. 3. Adjust the transmit power value with the UP/DOWN arrow keys. 4. Press F6 again to dekey the radio, and then press F8 to program the softpot value. Reference Oscillator AlignmentAdjustment of the reference oscillator is critical for proper radio operation. Improper adjustment will not only result in poor operation, but also a misaligned radio that will interfere with other users operating on adjacent channels. For this reason, the reference oscillator should be checked every time the radio is serviced. The frequency counter used for this procedure must have a stability of 0.1 ppm (or better). 1. Press F4 to select the REFERENCE OSCILLATOR softpot. 2. Press F6 to key the radio. The screen will indicate that the radio is transmitting. 3. Measure the transmit frequency that appears on the screen of your frequency counter. 4. Use the UP/DOWN arrow keys to adjust the reference oscillator. 5. Press F6 again to dekey the radio and then press F8 to program the softpot value. Transmitter Power1. Press F5 to select the Tx POWER calibration softpot. The screen will indicate the transmit test frequencies to be used. 2. Press F6 to key the radio. 3. Use the UP/DOWN arrow keys to adjust the transmit power value. 4. Press ENTER to select next softpot frequency. 5. Repeat steps 3 and 4 for the remaining test frequencies. 6. Press F6 to dekey the radio. 7. Press F8 to program the value.
6-4 Radio Tuning Procedure Transmit Deviation Balance (Compensation) & Deviation LimitCompensation alignment balances the modulation sensitivity of the VCO and reference modulation (synthesizer low frequency port) lines. Compensation algorithm is critical to the operation of signaling schemes that have very low frequency components (e.g. DPL) and could result in distorted waveforms if improperly adjusted. 1. Press F6 to select TX DEVIATION CALIBRATION. The screen will indicate the transmit test frequencies to be used. 2. Begin with the lowest test frequency shown on the screen. 3. Press F6 to key the radio. Record this measurement. 4. Press F4 to select 2.5 kHz. 5. Use the UP/DOWN arrow keys to adjust the deviation to within 0.5 dB of the value recorded in step 3. 6. Press ENTER to move to next softpot value. 7. Repeat steps 5 and 6 for the remaining frequencies. 8. Press F8 to program the softpot value. Transmit Deviation LimitThe transmit deviation limit softpot sets the maximum deviation of the carrier. Tuning is performed for 25 kHz channel spacing. 1. Begin with the lowest test frequency shown on the screen. 2. Press F6 to key the radio. 3. With Test Box 4460A: inject a 1 kHz tone, 2000 mVrms. 4. Use the UP/DOWN arrow keys to adjust the deviation to between 4.4 kHz and 4.8 kHz. 5. Press ENTER to move to the next softpot value. 6. Repeat steps 4 and 5 for the remaining frequencies shown on the screen. 7. Press F6 to dekey the radio. 8. Press F8 to program the softpot value. SquelchThe squelch softpots set the signal to noise ratio at which the squelch opens. 1. Press F9 to select SQUELCH Adjustment. 2. Adjust the UP/DOWN arrow key to the minimum squelch value. 3. Set the RF test generator to the test frequency plus +500 Hz offset. 4. Adjust the UP/DOWN arrow key until the squelch just closes. 5. Monitor for squelch chatter; if chatter is present, continue to adjust the UP/ DOWN arrow. Wait 500 msec and repeat step 4. 6. When no chatter is detected, press F8 to program this value. Ending the Tuning Procedure1. Press F2 to continue. 2. Press F10, F10 to return to the Service menu.
Theory of Operation 7-1 7Theory of Operation7 This chapter provides theory of operation information for the radio. It starts with a block diagram level functional description of the entire radio. This is followed by a detailed functional description for each of the four major functions that make up the radio. Introduction OverviewThis section provides a detailed theory of operation for the radio and its components. The main radio is a single board design, consisting of the transmitter, receiver, and controller circuits. The control head is mounted directly on the front of the radio. The control head contains a speaker, LED indicators, a microphone connector, buttons which provide the user with interface control over the various features of the radio and a display. In addition to the power cable and antenna cable, an accessory cable can be attached to a connector on the rear of the radio. The accessory cable provides the necessary connections for items such as external speaker, emergency switch, foot operated PTT, ignition sensing, etc.
7-2 Theory of OperationFigure 7-1 800-MHz Radio Functional Block Diagram Receiver Detailed Functional DescriptionThe receiver is composed of four sections: receiver front end, receiver IF, receiver back end and the audio signal Þlter IC (ASFIC) that is part of the controller section. The radio signal from the antenna switch in the PA section enters the Þrst bandpass Þlter (FL5203). The Þrst bandpass Þlter has three poles, a 860-MHz center frequency, a 20-MHz wide passband and a 40-dB rejection for image frequencies (761 to 780 MHz). After the Þrst bandpass Þlter, the signal passes to a pair of hot-carrier limiting diodes (D5303) placed in front of RF preampliÞer Q5301. The hot-carrier diodes limit strong signals to prevent them from overdriving the RF preampliÞer and damaging it. The front end ampliÞer is a low noise ampliÞer that consists of Q5301. Its main purpose is to set the noise Þgure of the receiver. The front end ampliÞer as well as the IF ampliÞers are shut off during transmit by K9.1 line via switch Q5230, to provide isolation in talk-around mode. CPU CLOCKMOD SPI MOD 2.1 MHZ SYNTHESIZER DIRECTIONAL COUPLER PRE-SELECTOR 3-POLE CERAMIC2-POLE IFBACK-ENDASFIC CPU KEYBOARD DISPLAYMEMORY POWER CONTROL HARMONIC FILTER AUDIO PA RF AMP PA LINEUP FRAC N IC LOOP FILTER T/R SWITCH PENDULUM 16.8 MHZ RX_TX VCO TA VCO PRE-SELECTOR 3-POLE CERAMIC SYNTHESIZER LINEUP PA RECEIVERAUDIO & LOGIC MIXER LO SIGNAL
Theory of Operation 7-3 Figure 7-2 Receiver Functional Block Diagram After the ampliÞer, the signal enters a second bandpass Þlter (FL5204), which is identical to FL5203. The bandpass Þlter is Þxed tuned from 851 to 870 MHz. After the second bandpass Þlter, mixer U5211 down-converts the signal to the IF frequency. The mixer is a passive double-balance mixer that gets a local oscillator signal in the range of 805.9 to 824.9 MHz from the synthesizer and works on 4-dBm power. The IF frequency is 45.1 MHz. A diplexer matches the mixer IF port to 50 Ohm out of the IF frequency band. The diplexer consists of R5401, C5404, L5402. The IF signal is fed to Þrst crystal Þlter Y5201 through matching network L5401, C5200. Crystal Þlter Y5201 has two poles. The crystal Þlter is followed by matching elements, that match the Þlter output impedance to the input impedance of IF ampliÞer Q5201. Following the IF ampliÞer is a matching network that matches the IF ampliÞer output impedance to the input impedance of a second 45.1-MHz crystal Þlter (Y5202). The second crystal Þlter is followed by matching elements that match the output of the second crystal Þlter to the input of the receiver back end circuits. After the matching circuit, the signal passes a pair of hot-carrier limiting diodes (D5201) placed in front of the back end circuit. The receiver back end consists of BBR IC (U5201) that contains the following functions: ¥PreampliÞer & mixer to convert the signal to a second IF frequency of 455 kHz. ¥Second LO circuit RF AMPDET_AUDIOIF AMPRSSI BPF 455 KHz N = 4 BW = 9 KHz IF BPF CRYSTAL 2-POLE LOSS = 2 dB REJ = 15 dB @ 25 KHz IIP3 = 10 dBm 2ND LO 44.654 MHZ GAIN = 21 dB NF = 3.3 dB IIP3 = 3 dBm LO_INJ C. LOSS = 7 dB PRE-SELECTOR 3 ELEMENTS CERAMIC FILTER SW 5 V K9.1 5V_REG 9V3 ADAPTPRE-SELECTOR 3 ELEMENTS CERAMIC FILTERIF BPF CRYSTAL 2-POLE NF = 7 dB IIP3 = 11 dBm LOSS = 1.5 dB REJ = -43 dB @ IMAGE GAIN = 16 dB NF = 1.8 dB BPF 455 KHz N = 4 BW = 10 KHz BBR LOSS = 2 dB REJ = 15 dB @ 25 KHz IIP3 = 10 dBm LOSS = 1.5 dB REJ = -43 dB @ IMAGE
7-4 Theory of Operation¥Second IF ampliÞers ¥FM Demodulator ¥Audio ampliÞer In addition to BBR IC, the back end contains the following components: ¥Second LO resonator for 44.645 MHz (Y5211) ¥Crystal Þlters for 455 kHz (FL5201, FL5202) ¥Demodulator Þlter (C5224) The IF signal routed to BBR IC is ampliÞed, converted to 455 kHz, Þltered, limited and demodulated. Demodulated audio comes out of BBR IC at pin 28 and is fed to the ASFIC, which is part of the radio controller section. In addition to the audio output signal, the receiver section provides an RSSI (Receiver Signal Strength Indicator) at pin 11. The RSSI signal is fed to the controller. ADAPT signal in pin 22 controls the BBR IC. The normally low (0 V) ADAPT signal is high (5 V) during change of radio channels or at turn-on. The ADAPT signal is used to control precharge of capacitor C5231 at DEMOD_OUT. This is done in order to eliminate the transient during a change in the frequency or when the radio goes from transmit to receive mode. Transmitter Detailed Functional DescriptionThe 15-W PA is a three-stage ampliÞer used to amplify the output from the injection string to the radio transmit level. It consists of driver stage Q6501, followed by two-stage Class C Power Module U6501. The two stages of the power module operate from the A+ supply voltage. The module is switched on/off by the K9.1 line through switch U6502 (which connects the A+ line to pin 2 of U6501 when transmit is enabled).The RF drive, which is routed into transistor Q6501, is controlled from Q6506 via the PA control line. The rising control voltage on the PA control line causes a rising collector voltage on Q6501. This causes more power out of the stage. Conversely, a decreasing control line voltage decreases the power delivered into the next stage. By controlling the drive power to U6501 and the following stages in the power ampliÞer lineup, ALC loop is able to regulate the output power of the transmitter. The antenna switch is switched synchronously with the keyed 9.1 voltage. In the transmit mode, this 9.1 voltage is highÑturning on diodes CR6502, CR6503 and CR6504. When CR6502 is turned on, it forms a low impedance to the RF transmit path and allows the signal to pass through. Diodes CR6503 and CR6504 short the ends of quarter wavelength lines to ground, presenting a high impedance towards the receiver. In this way no power is delivered into the receiver, the transmit path remains undisturbed, and the receiver is protected during transmission. In the receive mode, all these diodes are off. The off capacitance of CR6502 is tuned by L6508 to form a high impedance looking into the transmitter. Therefore, energy coming in the receive mode is channeled to the RX port. Harmonics of the transmitter are attenuated by the harmonic Þlter. The harmonic Þlter is formed by inductors L6513 and L6518 as well as capacitors C6540-C6542, C6551-C6553.
Theory of Operation 7-5 This network forms a low-pass Þlter to attenuate harmonic energy of the transmitter to speciÞcations level. A forward-power detector follows the harmonic Þlter. This forward-power detector is a microstrip printed circuit, which couples a small amount of the forward energy and sends it to diode CR6506 where it is rectiÞed. This rectiÞed signal (VFORWARD) forms the forward voltage which the power control circuit holds constant. Holding this voltage constant (which is proportional to the RF rectiÞed energy appearing across the diode) ensures the forward-power out of the radio is held to a constant value. In the PA section, 50k thermistor R6519 senses temperature in the area of the power module. This signal is fed back into the power control circuit to protect the power ampliÞer against over-temperature conditions. Resistor R6520, in series with the A+ line supply, feeds voltage to the power module. The voltage across R6520 is monitored and these two inputs are channeled to the power control circuit. The power control circuit monitors the voltage drop across this resistor, which is determined by the magnitude of the drain current in U6501. It uses this as a limiting mechanism whereby the power control circuit limits the magnitude of current that can be drawn by U6501. This protects the device from over dissipation. Bias voltage reverse polarity protection for the transmitter is provided by diode CR6508. Under reverse polarity conditions to the radio, this diode conducts and protects the radio from damage. This diode also provides transient over-voltage protection by breaking down when the supply voltage to the radio exceeds 24 V. Power Control CircuitryThe power control circuitry consists of three mechanisms. Power SetThe control loop compares the power output level to the pre-set value. The VFORWARD voltage from the forward power detector is ampliÞed by U0701 (pins 5 and 7) and compared to D/A U0702, outputs 2 and 4. Should a difference be detected, an error current is generated into the loop integrator (U0702, pins 8 and 10) until equilibrium is obtained. The use of 2 D/A outputs for power set (pins 2 and 4) enables Þne tuning where pin 2 is the coarse tune through resistor R0703 (10 kW) and pin 4 is Þne tune through resistor R0706 (100 kW). Current LimitThe current to the power module is monitored using R6520 and compared to a pre- set limit (D/A pin 11, and U0701 pins 1-3). When the limit is exceeded, an error current is generated through diode CR0721 (pins 1 and 3) to the loop integrator, which lessens the PA_CNTRL line and reduces the power ampliÞer output. Thermal ProtectionWhen the power module overheats, the resistance of thermistor R 6519 drops. Because of the voltage divider formed by R0725, R0721, and R6519, this resistance drop is sensed and ampliÞed through U0701 pins 12-14. This causes a current error through diode CR0721 pins 2 and 3 to ßow into the loop integrator and reduce transmitted output power. The PA_ENABLE line is for emergency shut down of transmission. When the line is driven high, transistor Q0731 is driven into saturation, causing the power control line to be driven to ground voltage. The K9.1_ENABLE line generates the K9.1 voltage when high enabling transmission.