GTX/LTS2000 Handheld Radio Service Manual Part 2 of 3
Contents
1. NO s U220 pin AT 13 VDC 45V at 0220 pins Is 16 8 2 Check Check 223 230 12 22 23 E signal at U210 C240 and CR220 amp 3 U220 pin 147 R210 C232 R232 Fix Connection lt i YES Is U220 pin 1 lt 0 7 VDC in RX amp 4 3 VDC in TX 2 Are signals at pins 9 amp 10 of 02207 Are waveforms NO at pins 9 amp 10 triangular Is connection between U220 pinl amp 0270 pin 6 Do pins 5 6 amp of U220 toggle when channel is changed Is U270 pin1 lt 0 7 V DC in 5 there a short Check U400 between pin 32 and RX and gt 47 pins 9 amp 10 of Check programming DC in TX lines between U709 Replace U220 and U220 pins 5 6 amp 7 Remove shorts NO s information from uP U709 s U220 pin 18 at 4 65 VDC Check U709 troubleshooting chart YES Replace U220 If pin 18 is properly Is RF level at soldered to the pin 20 PCB replace U220 between 10 amp 5 dBm If C271 and runners between YES U220 pin 20 amp U220 pin 15 are OK then see VCO troubleshooting chart Replace or Are C241 C243 resolder 245 247 C249 necessary C253 L246 components R242 R244 and R245 OK TX not at talk around2. Test Mode Entry Test Mode allows radio checks to be performed in the field To provide a level of protection to the Test Mode entry proceed according to the following sequence 1 Place radio in TRUNKING operation mode and wait for 6 seconds See Quick Start card for instructions on how to enter that mode 2 Turn radio off 3 Remove battery from radio 4 Plug the 25 pin end of the HKN9857 program ming cable into the RIB The other end of this cable has a battery eliminator 5 Put the battery eliminator in place of the radio battery 6 Verify that RIB is off 7 Turn radio power supply 7 5 V DC on NOTE You may use the programming cable bat tery as external power supply for the radio 8 Turn radio on The radio enters Test Mode operation e Speaker unmutes One beep is heard to indicate operation on the first test frequency default Display shows 4 1 CHANNEL MODE 4 IS INITIAL MODE Test Mode Channel Selection Use the PTT switch for channel selection A short press and de press on the PTT switch button like push will advance the radio to the next channel cyclical Seven channels are available during test mode as shown in the table below Table 5 1 900 MHz Test Mode Channel Selection Channel Number Rx Frequency Tx Frequency Display 1 935 0125 MHz 896 0125 MHz M 1 2 2 938 0125 MHz 899 0125MHz M 2 2 3 941 0000 MHz 902 0000MHz M 3
3. U550 D5 In addition it monitors the rate of change of RSSI Receive Signal Strength In signal in RSSI IN pin U550 F5 The discriminated audio signal DISC enters into the Hear Clear IC at U550 E4 The circuit then reduces the amount of popping Noise associated with fading The improved audio exits the IC at FFOUT pin U550 F4 The expander is used after de emphasis but before the ASFIC volume attenuation The Expander purpose is to transpose the compressed audio back to normal audio As with the compressor circuit the expander circuit adjusts the amplitude of a signal based upon its input amplitude NOT its frequency Note that an input of 191 mV will exit as 191 mV While a smaller signal will be made even smaller and a signal larger than 191 mV will exit EXPOUT even larger Example 100 mV EXPIN 52 mV EXPOUT 191 mV EXPIN 191 mV EXPOUT 250 mV EXPIN 327 mV EXPOUT Note this operation is NOT a function of frequency between 3 3 Khz 2 10 68P02948C90 O GTX GTX LTR LTS 2000 Portable Radios Service Manual Hear Clear IC U550 Data Signal Routing While transmitting all signals bypass the Hear Clear Compressor While receiving subaudible signals PL DPL LST go through the Flutter Fighter and ASFIC Inside the ASFIC the sub audible signaling is separated from the voice for decoding Sub audible signaling never goes through the expander While receiving other signals HST MDC MPT
4. not sub audible the Flutter Fighter is set to pass through mode the signal is routed from FFIN to FFOUT without any adjustment February 1997 Section 3 Accessory Overview The remote speaker microphone is an accessory avail able with the GTX GTX LTR LTS 2000 portable radios This section provides a general description of the remote speaker microphone and describes the operation handling precautions and maintenance of this accessory Description Model HMN9725 Remote Speaker Microphone includes a speaker a microphone a push to talk PTT switch and associated circuitry A cable terminated with a special plug is provided for attaching to the accessory connector on the portable radio When the remote speaker microphone is attached to the radio the speaker in the radio is disabled and receiver audio is connected to the accessory speaker Similarly the accessory microphone is connected to the transmitter and the accessory PTT switch can now control the PTT function in the radio The radio micro phone and PTT switch are still operational but you can listen to the radio only through the accessory speaker IMPORTANT Observe safety information in the radio operating instructions Operation 1 Attach the microphone s accessory connector to the accessory connector on top of the radio 2 While listening to the accessory speaker turn the radio on 3 Operate radi
5. to be tested 5 4 RF level set to 1mV RF As above except change frequency to a conventional system Raise RF level from Zero until radio unsquelches Same as Above out of TEST MODE select a conventional system PTT to OFF center meter selection to Audio PA spkr load to speaker Same as Above Set volume control to 2 84 Vrms Unsquelch to occur at lt 0 3 uV Preferred SINAD lt 12 dB 68P02948C90 O February 1997 Section 6 Maintenance Introduction This section of the manual describes preventive maintenance safe handling of CMOS devices and repair procedures and techniques Each of these topics provides information vital to the successful operation and maintenance of your radio Preventive Maintenance GTX GTX LTR and LTS2000 radios do not require scheduled preventive maintenance program however periodic visual inspection and cleaning is recommended Inspection Check that the external surfaces of the radio are clean and that all external controls and switches are functional A detailed inspection of the interior electronic circuitry is neither needed nor desired Cleaning The following procedures describe the recommended cleaning agents and the methods to be used when cleaning the external and internal surfaces of the radio External surfaces include the front cover housing assembly and battery case These surfaces should be cleaned
6. 2 1 MHz input on U701 P38 which comes from the transceiver board the ASFIC outputs a 7 776 MHz CMOS square wave 0 5Vpp logic on U701 P30 which connects to the EXTAL input of the microprocessor U709 P73 The microprocessor oper ates at 1 4 of this frequency which in this case com putes to 1 944 MHz In particular the E clock output U709 P72 will be a 50 duty cycle square wave at this frequency Bus Operation The microprocessor operates in expanded memory mode and executes firmware contained in OTP FLASH ROM U705 The microprocessor uses a non multiplexed address data bus consisting data lines DO through D7 and address lines 0 17 In addition the microprocessor has integrated chip select logic so that external memories can be accessed without the need for external address decoder gates These chip select signals are provided by U709 P28 and P29 When the controller board is functioning normally microprocessor s address and data lines should be tog gled at CMOS logic levels Specifically the logic high levels should be between 4 8 and 5 0V and the logic low levels should be between 0 and 0 2V RAM The on chip 768 byte static RAM from U709 provides some scratch pad memory with the bulk of it coming from the external 8 or 32Kbyte SRAM 0706 External SRAM accesses are indicated by the U709 P28 Nor mally SRAM is accessed less often than the OTP FLASH ROM 0705 i e the number of transitions per second on U
7. IC The Hear Clear HC is typically used for 900 MHz radios The HC has three main circuit blocks within the IC 1 Compressor 2 Flutter Fighter 3 Expander Cir cuits There are six enable control lines on the HC which determine its mode of operation The remaining five lines are controlled by the HC_CNTL line of DAC U1400 15 The table below summarizes the logic controls and the IC states Table 2 1 Logic State Name Ref Des Set By 1 RX1 TX2 RX2 ICENABLE U550 C4 SWB 1 1 x 1 FFENAB U550 E3 HC_CNTL 1 1 x 0 LODSAB U550 A5 HC_CNTL 1 1 1 x HIENAB U550 C2 GND 0 0 X 0 HCIDSAB U550 B6 HC_CNTL 1 1 1 1 CPNENAB U550 D1 HC_CNTL 1 1 X 0 TX1 transmit mode with carrier squelch PL or DPL RX1 receive mode with carrier squelch PL or DPL TX2 transmit mode with all data HST MDC MPT amp DTMF RX2 receive voice with all data HST MDC MPT amp DTMF February 1997 GTX GTX LTR LTS 2000 Portable Radios Service Manual Transmit Path for Radio with Hear Clear TX audio signal comes from microphone and enters the ASFIC MIC U701 B6 The audio signal from the ASFIC is routed to ASFIC pin U701 H5 from where it leaves the ASFIC and enters the Hear Clear compressor at pin U550 D3 The compressed signal leaves Hear Clear at pin U550 F3 COMP OUT where it is routed back to the ASFIC TX pin U701 C7 C561 provides AC coupling Inside the AS
8. J200 to the synthesizer U201 pin 8 TX Data Circuits There are four major types of transmit data sub audi ble data PL DPL Connect Tone that gets summed with voice high speed data for trunking control chan nel communication DTMF data for telephone commu nication in trunked and conventional systems and MDC data for use in Motorola proprietary MDC sys tems The deviation levels of the latter three types are tuned by a 5 bit digital attenuation inside the ASFIC For each data type and each band split there is a dis tinct set of tuning values that are programmed into the ASFIC before the data is generated and transmitted February 1997 GTX GTX LTR LTS 2000 Portable Radios Service Manual Sub Audible Data PL DPL Sub audible data is composed of low frequency PL and DPL waveforms for conventional operation and con nect tones for trunked voice channel operation The trunking connect tone is simply a PL sine wave at a higher deviation level than PL in a conventional sys tem Although it is referred to as sub audible data the actual frequency spectrum of these waveforms may be as high as 250 Hz which is audible to the human ear However the radio receiver filters out any audio below 300 Hz so these tones are never heard in the actual sys tem Only one type of sub audible data can be generated by U701 at a time The process is as follows using the SPI the microprocessor programs the ASFIC U701 to set up the pr
9. Page IX Voice Modulation Mode PWR MON 4th channel test frequency atten to 70 input to rf In Out Monitor DVM AC Volts Set 1kHz mod Out level for 0 025Vrms at test set 80mVrms at AC DC test set jack TEST MODE Display 2 0 Same as Above meter selector to mic Deviation 800 MHz 23 6 kHz but lt 5 0 kHz 900 MHz lt 2 5 kHz Low Speed Data Modulation 800 900 Same as Above TEST MODE Display 2 1 PTT to continuous during the performance check Deviation 800 MHz 2800 Hz but lt 1200 Hz 900 MHz gt 350 Hz lt 650 Hz Voice Modulation Internal Mode PWR MON 2nd channel test frequency atten to 70 input to RF In Out TEST MODE Display 2 0 Remove modulation input Press PTT switch on radio Say four loudly into the radio mic Measure deviation 800 MHz 23 8 kHz but lt 5 0 kHz 900 MHz lt 2 5 kHz High Speed Data Modulation Same as Above TEST MODE Display 2 2 PTT to continuous during the performance check Deviation 800 MHz 22 3 kHz but lt 3 8 kHz 900 MHz 21 2 kHz but lt 2 kHz DTMF Modulation SIGN Same as Above 2nd channel test frequency TEST MODE Display 2 3 output at antenna Same as Above Deviation 800 MHz 22 8 kHz but lt 3 8 kHz 900 MHz 21 4kHz but lt 1 9 kHz PL DPL Modulation radios with conventional coded squelch operation only Change frequency to a conventional transmi
10. frequency Troubleshooting Flow Chart for Synthesizer 4 4 68P02948C90 O February 1997 GTX GTX LTR LTS 2000 Portable Radios Service Manual Apply power to radio and turn on Are alert tones ee enabled with RSS now Use RSS to enable tones Yes Are alert tones enabled with RSS Check radio con nection to RIB and computer gt RIB radio connections OK Was good power on beep present Troubleshooting Charts Reprogram radio with RSS Apply power to radio and turn on Was good power on beep present replaced Main radio board must be With power connected to radio and the radio turned on check the following 1 5 V at pin 4 of U704 and pin 71 12 31 41 of U709 2 Check for 14 7456 MHz at pin 73 of U709 3 Check DC at pin 75 of U709 If lt 4 5V DC check J700 pin 238 for 2 1 MHz signal 4 Check for typical voltages of U709 and U701 Are tones present on power up at U700 pin 18 RX AUDIO February 1997 Done Audio problem Trouble shoot audio circuitry 68P02948C90 O Troubleshooting Flow Chart for Controller 4 5 Troubleshooting GTX GTX LTR LTS 2000 Portable Radios Service Manual This page intentionally left blank 4 6 68P02948C90 O February 1997 Section 5 Radio Diagnostic Utilities
11. pin is one of the eight chan nels of U709 s 8 bit A D convertor After passing through the 8 bit digital attenuator the audio goes to buffer amplifier and then exits at U701 J4 where it is routed to the Audio power amplifier circuit in the transceiver board 68P02948C90 O 2 7 Theory of Operation Controller Audio Power Amplifier Resistor R466 sets the input impedance to U409 P2 of the audio power amp The audio PA circuit is a bridged tied load BTL configuration with fixed gain of 40dB devel oping 500mW rated audio power output at less than 5 harmonic distortion into the 16 Ohm internal speaker LS401 with nominal 7 5 V DC battery supply Maximum audio power output is greater than 1 2 W Audio PA Muting and Output Protection PNP transistor Q410 the audio PA power switch driven by NPN darlington transistor Q411 the PA mute amp controls Vcc supply to Audio PA U409 P1 U701 A3 is connected to Q411 base controlling audio PA Vcc supply Resistors R489 and R490 PNP transistor 0412 and the current sense circuit monitor current supplied to audio PA U409 P1 Worst case audio PA current at 9 V DC bat tery voltage maximum volume and full system devia tion does not exceed 450 mA at the nominal 16 Ohm load Resistor R488 and capacitor C461 provide an RC time delay for U405 2 a monostable multivibrator cir cuit A 2 5 V DC reference voltage is fed to U405 2 P6 On radio power up and in normal operation U405 P7 monostab
12. solder pads with alcohol and a small brush Dry and inspect Ensure that all solder is removed Once the preparation is complete place the circuit board back in the R 1319A s circuit board holder Add solder paste flux in the trench of the flux block and spread it using a one inch putty knife Flux the OMPAC by placing it in the trench of the flux block Once the flux is applied place the OMPAC on the circuit board making certain that it is oriented correctly on the board Position the heat focus head over the OMPAC and lower it to approx 68P02948C90 O done with the R 1319A using the same heat and airflow profile used to remove and replace OMPAC components Place the circuit board in the R 1319A s holder Select the proper heat focus head and attach it to the heater chimney Add solder paste flux around the base of the shield Position the shield under the heat focus head Lower the vacuum tip and attach it to the shield by turn ing on the vacuum pump Lower the focus head until it is approximately 1 8 0 3cm above the shield Turn on the heater and wait until the shield lifts off the circuit board Once the shield is off turn off the heat grab the part with a pair of tweezers and turn off the vac uum pump Remove the circuit board from the R 1319A s circuit board holder To replace the shield add solder to the shield if necessary using a micro tipped soldering iron Next rub the soldering iron tip along the edge of
13. the shield to smooth out any excess solder Use solder wick and a soldering iron to remove excess solder from the solder pads on the circuit board Place the circuit board back in the R 1319A s circuit board holder Place the shield on the circuit board using a pair of tweezers Position the heat focus head over the shield and lower it to approximately 1 8 above the shield Turn on the heater and wait for the solder to reflow Once complete turn off the heat raise the heatfocus head and wait approximately one minute for the part to cool Remove the circuit board and inspect the repair No cleaning should be necessary 6 3
14. 0 U4 FFIN through capacitors C500 and C567 C567 is a part of a noise sampling cir cuit consisting of components C567 R556 R553 C564 R555 R557 and C565 and Hear Clear ports CLIP REF NFILIN NFILOUT and NOISHLD After exiting Hear Clear at the FFOUT pin U550 F4 the signal enters ASFIC at RX pin U701 H6 Within the ASFIC the signal passes through LPF and HPF lim iting the audio bandwidth to 0 3 3 Khz de emphasis and exit the ASFIC at UNAT_RX pin U701 H5 After exiting the ASFIC at UNAT_RX the signal passes through the AC coupling capacitor C550 and is routed to the Hear Clear pin EXPIN U550 C1 which is Expander input buffer The Expander output signal EXPOUT at pin U550 A2 is a normalized received audio signal which is routed back to the ASFIC through the AC coupling capacitor C560 for volume adjustment at pin EXP_AUDIO U701 J5 The adjusted signal exits ASFIC at pin RX AUDIO U701 J4 and is routed to the Audio Power Amplifier HEAR CLEAR Exp Exp In Out In AUDIO POWER AMPLIFIER Rx Aud Out ASFIC Hear Clear Receive Path 68P02948C90 O 2 9 Theory of Operation Controller The purpose of Flutter Fighter is to sample the amount of Noise in the receive audio between 10 20 Khz using the Noise Filter IN pin FFIN U550 E4 Noise Filter Out the leg FFOUT U550 C6 and Noise Hold the pin NOISHLD
15. 1505172Q01 Housing back 0484345A06 Washer 3 used 0305137Q02 Screw Phillips 3 used 0105959954 Belt clip assembly 0300139982 Screw Phillips 4 used NNR RR eR AND UI Figure 3 3 Exploded View February 1997 68P02948C90 O 3 3 Accessory GTX GTX LTR LTS 2000 Portable Radios Service Manual This page intentionally left blank 3 4 68P02948C90 O February 1997 Section 4 Troubleshooting Overview This section contains three troubleshooting tables for the following GTX LTS 2000 components e Receiver Transmitter Synthesizer Controller Troubleshooting Charts Refer to following pages February 1997 68P02948C90 O 4 1 Troubleshooting GTX GTX LTR LTS 2000 Portable Radios Service Manual Troubleshooting Charts Very low orno 12 Check IFIC dB SINAD U51 see NO below Is 2nd LO on 1 Noise at spkr Noise at pin 23 when radio is of IFIC U51 Check VDC of angau NO all IFIC pins Check 2nd LO XTAL and components Check ASFIC Is Ist LO Check Check IFIC 8 VCO Synth see below Check external Inject on channel Check external components signal at RF port components connected to IFIC 050 connected to IFIC If OK replace U51 Inject on Channel signal at pin 1 of Front End filter
16. 2 4 1 CC1 45 MHz 4 2 5 CC1 2 CC1 45 MHz 5 2 6 1 3 CC1 45 MHz M 6 2 7 4 CC1 45 MHz M 7 2 1 CC1 CC4 are control channels programmed in association with the selected trunking system 2 M stands for modulation type 0 3 see Table 5 2 Channel numbers 4 through 7 do not apply to LTR Models 68P02948C90 O 5 1 February 1997 Radio Diagnostic Utilities Test Mode Tx Modulation Test Mode Tx Modulation Use PTT switch for modulation type selection A con tinuous press will advance the radio to the next modu lation test cyclic scroll and perform Tx test till PTT is released The modulation selection is described in the table below GTX GTX LTRLTS 2000 Portable Radios Service Manual Table 5 2 Test ModelTx Modulation Modulation Type Internal Speaker Audio Signaling Internal Microphone Status Display CSQ None On 1 Low Speed None On 1 1 High Speed Call Back Off 2 1 DTMF Off 3 1 C stands for the selected channel 1 7 see Table 5 1 Fail Mode Non critical errors will be temporarily indicated as The radio will enter Fail Mode upon detecting one of the following errors e Application start up self check error Codeplug information check error There are two categories of errors critical and non crit ical Critical errors will stop radi
17. 705 chip select pin 30 should be 5 15 times higher than those on U706 pin 20 EEPROM The radio codeplug storage is provided by U709 inter nal 640 byte EEPROM with an additional 4K byte of 68P02948C90 O 2 5 Theory of Operation Controller memory space provided by external EEPROM U703 There are three basic types of codeplug information information on the trunked system on which the radio is authorized to operate information on the conven tional system which is either of the repeater or talk around type on which the radio is authorized to oper ate and information on the configuration and tuning of the radio itself Tuning information is normally located in the internal EEPROM of U709 SPI Interface The microprocessor communicates with several ICs and modules through a dedicated on chip serial peripheral interface SPI port which consists of trans mit data line MOSI U709 P1 receive data line MISO U709 P80 and clock line SCK U709 P2 In addition each IC that can be accessed by the microprocessor using the SPI read write select line associated with it The ICs or circuits and their associated select lines are e EEPROM 0703 with select line U709 P3 e ASFIC U701 with select line U709 P34 e LCD Driver U707 with select line U709 P23 e OTP FLASH ROM 0705 with select line U709 P29 e SRAM U706 with select line U709 P28 Transceiver Board Synthesizer U201 with select line U709 P35 e Transceive
18. FIC the signal is routed through a LPF and HPF that limits the signal between 0 3 3KHz The signal is then pre emphasized and exits the ASFIC PRE_AMP at pin U701 C8 and routed back to ASFIC at LIM pin U701 E8 where it is routed through the limiter splatter filter and two attenuators which set the amplitude deviation level of the signal The purpose of having a compressor in the transmit mode is twofold 1 improve S N ratio for low level audio and 2 maintain the same dynamic range of 12 5 KHz bandwidth channel as obtained in the 25 KHz channel The compressor raises low level signals and lowers high level signals The compressor circuit produces a signal whose output voltage at pin U550 F3 is based on the input voltage of the signal at pin 0550 03 It is not a function of the frequency as in pre emphasis The transfer function is COMP OUT SQRT 80 MIC_IN Note 80 mV input provides 80mV output e g 20 mV input 40 mV output 80 mV input 80 mV output 150 mV input 110 mV output HEAR CLEAR CBUFIN COMPOUT Accessory Connector UNAT_RX TX External MIC Hear Clear Transmit Path February 1997 TheorpO peration Controller Receive Path for Radio with Hear Clear The audio signal enters the Hear Clear controller from BBR signal DET_AUDIO at pin U51 28 The discrim inator audio signal DISC enters the Hear Clear Flut ter Fighter pin U55
19. FL1 s 12 dB SINAD 112 dBm YES Inject signal at IF Port of mixer Check U50 at 45 1 MHz harmonic filter and antenna path _ 3 7VDC at Check 5R een and Q405 Check mixer components 01 and externa Injecta 45 1 MHz signal at components NO Check 5R and IF amp components Check XTAL filters Y51A amp Y51B Troubleshooting Flow Chart for Receiver 4 2 68P02948C90 O February 1997 GTX GTX LTR LTS 2000 Portable Radios Service Manual Replace PA module February 1997 YES s Power Ou of pin5 atPA OK y YES Troubleshooting Charts Is the LED s red light on or not NO Inspect 1 Front cover flexible circuit 2 Voltage regulator Is biasing o Q400 OK Is control voltage high or low s PA drive OK 1 Check coupler U111 2 Check PIN diodes 3 Check harmonic filter Replace Inspect repair TX output network module 68P02948C90 O Replace Q400 LOW Troubleshoot Power Control circuit Troubleshoot VCO Troubleshooting Flow Chart for Transmitter 4 3 Troubleshooting GTX GTX LTR LTS 2000 Portable Radios Service Manual Troubleshooting Charts Correct problem check of the board OK Check 5V gt Regulator
20. GTX GTX LTR LTS 2000 P ortable Radios Service Manual SR 5 V MIXER 1ST 2ND RXIN __ 3 BANDPASS BANDPASS gt FILTER FILTER LO 3 dBm 1ST 2ND DETECTED AUDIO CRYSTAL CRYSTAL FILTER FILTER RECEIVER BLOCK DIAGRAM RX IN 0 dBm POWER ANTENNA HARMONIC ANTENNA FROM P MODULE COUPLER switcu FILTER P MATCHING VCO BUFFER V control RECTIFIER gt lt POWER CONTROL REFERENCE FROM DAC February 1997 TRANSMITTER BLOCK DIAGRAM 68P02948C90 O TheorpO peration Transmitter Theory of Operation Frequency Generation Unit The antenna switch circuit consists of two PIN diodes CR161 and CR162 a pi network C126 L161 and part of C162 and one current limiting resistor R163 In the transmit mode TX B is applied to the circuit to bias the diodes on The shunt diode CR161 shorts out the receiver port and the pi network which oper ates as a quarter wave transmission line transforms the low impedance of the shunt diode to a high imped ance at the input of the harmonic filter In the receive mode the diodes are both off and hence there exists a low attenuation path between the antenna and receiver ports The harmonic filter consists of part of C122 L121 and C123 This filter attenuates the harmonic of the module to a level better
21. ake longer than 60 seconds Once the carrier reflows raise the heat focus head and wait approximately one minute for the part to cool Remove the circuit board and inspect the repair No cleaning should be nec essary focus head approximately the same size as Shields the OMPAC Attach the heat focus head to the chimney heater Adjust the temperature 1 Removing and replacing the shields will be control to approximately 415 F 215 C 445 F 230 C maximum Adjust the airflow slightly above the minimum setting Apply the solder paste flux around the edge of the OMPAC Place the circuit board in the R 1319AR 1319A s circuit board holder and position the OMPAC under the heat focus head Lower the vacuum tip and attach it to the OMPAC by turning on the vacuum pump Lower the heat focus head until it is approximately 1 8 0 3cm above the carrier Turn on the heater and wait until the OMPAC lifts off the circuit board Once the part is off grab it with a pair of tweezers and turn off the vacuum pump Remove the circuit board from the R 1319AR 1319A s circuit board holder To replace the OMPAC the solder pads on the board must first be cleaned of all solder to ensure alignment of the new chip carrier Prepare the sight by using solder wick and a soldering iron to remove all solder from the solder pads on the circuit board If a power desoldering tool is available it can be used instead of the solder wick Clean the
22. ay Driver e 0704 5 V Voltage Regulator e U550 Hear Clear U709 U703 U705 U706 and U707 are powered by U704 U701 is powered from a 5V Regulator U708 on Radio Module In addition to the external memory devices U709 has 768 bytes of RAM and 640 bytes of EEPROM Functions The microprocessor has two basic functions interfac ing with the outside world and controlling the internal workings of the radio The microprocessor interfaces directly with the keypad side buttons PTT rotary switch low battery indicator EXT PTT and volume sense The microprocessor constantly monitors these inputs and interprets any changes into commands that control the rest of the radio Some control functions it performs include loading the synthesizer with the desired RF frequency turning the RF PA on or off February 1997 TheorpO peration Controller enabling and disabling audio and data paths and gen erating tones Operations and operating conditions within the radio are interpreted by the microprocessor and fed back to the operator as visible the display or audible alert tone indications of current status Normal Operation The regulated 5V output from U704 powers the micro processor U709 and the rest of the digital IC except ASFIC U701 The microprocessor s clock is generated by the ASFIC which has a built in programmable clock synthesizer Clock Synthesizer Upon power up and assuming that the ASFIC receives a proper
23. d piece approximately 1 8 above the component and begin applying heat Once the solder wicks to the component remove the heat and inspect the repair All joints should be smooth and shiny Over Molded Pad Array Carrier OMPAC CAUTION ASFIC 0701 is OMPAC It must be kept in a sealed bag with desiccant in the bag in a dry box as supplied by the Motorola Parts Department prior to use If the OMPAC is ambient for an unknown amount of time or for more than 96 hours then it must be baked for at least eight hours at 260 F 185 C CAUTION If neighboring OMPAC components are heated above 365 F 185 they will suffer die bond delamination and possi ble popcorn failure February 1997 GTX GTX LTR LTS 2000 Portable Radios Service Manual Repair Procedures and Techniques During all repair procedures heating neighboring components can be minimized by imately 1 8 0 3cm over the carrier Using the same heat and airflow setting used to remove the OMPAC turn on the heater and Using upper heat only using the correct size wait for the carrier to reflow heating and February 1997 heat focus head approximately the same size as the carrier being replaced Keeping the heat focus head approximately 1 8 0 3cm above the printed circuit board when removing or replacing the device To remove the OMPAC select the R 1319A Air Flow Station and the appropriate heat reflow should t
24. e Control The radio s RF circuit are constantly producing an out put at the Detected Audio line Whenever the radio is in trunked standby mode itis processing data from the control channel while in conventional standby mode it is always monitoring the squelch line and or sub audible data The detected audio from the transceiver board enters the controller board at connector J700 pin 4 In addition to the detected audio line the trans ceiver board also provides a squelch noise from U51 P30 into the ASFIC squelch detect circuitry via U701 H7 When the microprocessor determines that it has received the proper data or signal type for unsquelch ing it sets up the receive audio path and sends data to U701 to do the same within The detected audio will enter U701 through RX IN pin H6 and PL IN pin J7 for further processing Inside the IC the signal first passes through a low pass filter to remove any frequency components above 3000 Hz and then a high pass filter to strip off any sub audible data below 300 Hz Next the recovered audio passes through a de emphasis filter to reduce the effects of FM noise Finally the IC amplifies the audio and passes it through the 8 bit programmable attenuator whose level is set depending on the value of the volume con trol The microprocessor U709 programs the value of the 8 bit attenuator in accordance with the voltage sensed at the volume potentiometer which is con nected to U709 P48 This
25. e 0180381B45 Repair Station select the TJ 65 mini thermojet hand 6 2 68P02948C90 O GTX GTX LTR LTS 2000 Portable Radios Service Manual piece On either unit adjust the temperature control to 700 F 370 C and adjust the airflow to a minimum setting Airflow can vary due to component density 1 remove a chip component select a hot air hand piece and position the nozzle of the hand piece approximately 1 8 above the component to be removed Begin applying the hot air Once the solder reflows remove the component using a pair of tweezers Using solder wick and a soldering iron or a power desoldering station remove the excess solder from the pads 2 replace a chip component using solder ing iron select the appropriate micro tipped soldering iron and apply fresh solder to one of the solder pads Using a pair of tweezers position the new chip component in place while heating the fresh solder Once solder wicks onto the new component remove the heat from the solder Heat the remaining pad with the soldering iron and apply solder until it wicks to the component If necessary touch up the first side All solder joints should be smooth and shiny 3 To replace a chip component using hot air select the hot air hand piece and reflow the solder on the solder pads to smooth it Apply a drop of solder paste flux to each pad Using a pair of tweezers position the new compo nent in place Position the hot air han
26. entional operation External PTT Sense Circuits On connecting an external MIC through connector J3 external PTT sense transistor Q408 switches ON when the external PTT switch is closed Q408 collector voltage is monitored by U709 P4 When collector volt age is logic HIGH the microprocessor configures the radio for transmit mode In PTT equipped accessories the PTT switch is series connected with the external MIC element MIC Amplifier MIC audio from internal MIC MK401 is coupled through C429 L404 J3 and L403 to the MIC buffer cir cuit U405 1 External MIC plug insertion mechanically disconnects the internal MIC External MIC audio is coupled through L403 to the MIC buffer input The buffer will route the MIC audio into MIC IN U701 B8 through flex and connectors J200 and J700 Inside the ASFIC the MIC audio is filtered to eliminate compo nents outside the 300 3000 Hz voice band pre empha sized and then limited The limited MIC audio is then routed through a summer which is used to add in PL or DPL sub audio band modulation and then to a splatter filter to eliminate high frequency spectral com ponents generated by the limiter After the splatter fil ter the audio is routed to the 8 bit modulation attenuators which are tuned in the factory of the field to set the proper amount of FM deviation The TX audio emerges from the ASFIC at U701 J4 and is coupled and applied through flex and connectors J700
27. er U270 Tx output and provides the local oscillator LO injection signal for the Rx injection buffer U270 Rx out put The phase locked loop PLL circuit is provided by the fractional N synthesizer IC The output of the VCO is amplified by the prescaler buffer routed through a low pass filter and applied to the prescaler dividers of the synthesizer The divide ratios are determined from information stored in mem ory and bussed to the synthesizer by way of the micro controller The divide ratio determines the VCO frequency The resulting VCO buffer signal is applied to a comparator located in the synthesizer The synthe sizer comparator also receives a reference frequency by SWITCHING CCTS FOR VCO AND BUFFER RX VCO 16 8 MHz RXOUT RX IN MU REF OSC BUFFER BB MIXER 0210 RX BUFFER LOOP REFERENCE gt gt 4 gt BIDDER FILTER er hl gt NAT ENG Lp RF PA COUNTER FOR MOD OUT MULTIPLIER TX VCO TX BUFFER FRACTIONAL PRE SCALER 0260 AD P DIVIDER DIVIDER vco BUFFER 0220 0270 FRACTIONAL N VCO BUFFER IC SYNTHESIZER LOW PASS FILTER 2 1 MHz REFERENCE CLOCKTO MODULATING ASFIC SIGNAL FGU CIRCUITS 2 4 68P02948C90 O February 1997 GTX GTX LTR LTS 2000 Portable Radios Service Manual way of refe
28. hand be used if it is chip 82 5 necessary to touch the microphone cartridge 2113740A67 chip 330 pF 5 50V and associated wiring 2113741 53 chip 022 uF 5 50V 2113741869 chip 1 5 50V L1 2462575A02 chip inductor 680 nH 10 coil rf L2 2462575A02 chip 680 nH 10 L3 2462575A02 chip 680 nH 10 L4 2462575A02 chip 680 nH 10 switch 51 3905834K06 dome PTT miscellaneous MK1 0180703Y69 microphone assembly LS1 5005910P05 speaker L2 11 S1 PTT YY Y 2 5 mm plug Tip Cl C2 C3 AM YY Y ______ 2 5 mm plug Sleeve L3 14 3 5 mm plug C4 Tip 3 5 mm plug Sleeve LS1 Figure 3 2 Schematic Diagram 3 2 68P02948C90 O February 1997 GTX GTX LTR LTS 2000 Portable Radios Service Manual Maintenance Mechanical Parts List HMN 9725 Remote Speaker Microphone REFERENCE MOTOROLA SYMBOL PART NO DESCRIPTION 1 0105953N42 Front Housing items 1 thru5 2 3305259Q01 Nameplate Motorola 3 4505182Q01 Lever PTT 4 3505152701 Grille cloth 5 1105461R01 Adhesive 6 0180703Y70 Coil cord amp connector 7 0180703 Y67 PCB Includes electrical parts 8 3905834K06 Switch dome PTT S1 9 3205231Q01 Seal dome 2 1 10 1405219Q01 Boot microphone 11 0180703Y69 Microphone assembly 2 0 12 5005910P05 Speaker LS1 13 7505283Q02 Pad speaker 3205690 01 Gasket 6405689R01 Plate housing mounting 0300139982 Screw Phillips 2 56 x 5 32
29. hat controls or tunable components are not soaked with the liquid Do not use high pressure air to hasten the drying process since this could cause the liquid to puddle and collect in unwanted places Upon completion of the cleaning process use a soft absorbent lintless cloth to dry the area Do not brush or apply any isopropyl alcohol to the frame front cover or back cover NOTE Always use a fresh supply of alcohol and a clean container to prevent contamina tion by dissolved material from previ ous usage Safe Handling of CMOS Devices Complementary metal oxide semiconductor CMOS devices are used in this family of radios While the attributes of CMOS are many their characteristics make them susceptible to damage by electrostatic or 68P02948C90 O 6 1 Maintenance Repair Procedures and Techniques high voltage charges Damage can be latent resulting in failures occurring weeks or months later Therefore special precautions must be taken to prevent device damage during disassembly troubleshooting and repair Handling precautions are mandatory for CMOS circuits and are especially important in low humidity conditions DO NOT attempt to disassemble the radio without first referring to the CMOS CAUTION paragraph in the Disassembly and Reassembly section of the manual Repair Procedures and Techniques Refer to the Disassembly and Reassembly section of the manual for pertinent information prior to replacing and substi
30. he ground lead Ifthe microphone cartridge is removed from the unit place it on a conductive surface such as a sheet of aluminum foil which is connected to ground through 100k ohms of resistance WARNING If the aluminum foil is connected directly to ground be cautious of possible electri cal shock from contacting the foil at the same time as other electrical circuits e When soldering be sure the soldering iron is grounded e Prior to replacing circuit components or touch ing the microphone cartridge be sure to dis GTX GTX LTR LTS 2000 Portable Radios Service Manual Replacement microphone cartridges should be kept in conductive packaging until they are placed in unit Maintenance Refer to the schematic diagram shown in Figure 3 2 the exploded view shown in Figure 3 3 on page 3 3 and the parts lists Every part in the microphone is identified and illustrated for assistance in removal and replacement If necessary the external surfaces of the remote speaker microphone may be cleaned with a 0 5 solution of mild dishwashing detergent in water one teaspoon of detergent in a gallon of water Electrical Parts List HMN 9725 Electrical Parts List REFERENCE MOTOROLA charge any static buildup Since voltage SYMBOL PART NO DESCRIPTION differences can exist across the human body it is capacitor fixed 10 100 V un recommended that only one
31. ing high speed appears at U701 G4 where it connects to U709 P11 The low speed limited data output PL DPL 2 8 68P02948C90 O GTX GTX LTR LTS 2000 Portable Radios Service Manual and trunking low speed appears at U701 A4 where it connects to U709 P10 Alert Tone Circuits When the microprocessor needs to give the operator feedback for a good key press or for a bad key press or radio status trunked system busy low battery condition phone call circuit failures it sends an alert tone to the speaker It does so by sending data to U701 which sets up the audio path to the speaker for alert tones The alert tone itself can be generated in one of two ways inter nally by the ASFIC or externally using the microproces sor and the ASFIC The allowable internal alert tones are 300 900 and 1800 Hz For external alert tones the micro processor can generate any tone within the 100 3000 Hz audio band This is accomplished by the microprocessor toggling the output line U709 P7 which is also the same line used to generate low group DTMF data Inside the ASFIC this signal is routed to the external input of the alert tone generator The output of the generator is summed into the audio chain just after the RX audio de emphasis block The tone is then amplified and filtered before passing through the 8 bit digital volume attenua tor The tone exits at U701 J4 and is routed to the audio PA circuitry in the transceiver board Hear Clear
32. le multivibrator output is logic LO pulling Q411 emitter to Vee with the audio PA controlled by U701 A3 Should U409 P5 and or U409 P8 become shorted to each other or to the ground Vee current con sumption exceeds 500 mA approximately and Q412 collector When U405 2 P5 voltage rises higher than the U405 2 P6 reference voltage rise time is less than 50 usec U405 2 is triggered and U405 2 P7 output volt age is switched to 4Vdc effectively biasing Q411 into cut off and turning off the audio PA power switch Q410 U405 2 P7 remains in this state for 15 msec then reset to logic LO state Average power dissipation in the audio PA circuit components is helped to a low level by the low duty cycle less than 0 3 of the audio PA protection cir cuit The cycle repeats until the audio PA output short is removed Receive Data Circuits The ASFIC U701 decodes all receive data which includes PL DPL low speed trunking MDC and high speed trunking data The decode process for each data type typically involves low pass or band pass filtering signal amplification and then routing the signal to a comparator which outputs a logic zero or one signal The detected audio from the transceiver board is routed to U701 H6 and J7 through coupling cap C435 Inside U701 the data is filtered according to the data type HS data or LS data then hard limited to a 0 5V digital level The high speed limited data output MDC and trunk
33. o according to operating instruc tions supplied with the radio NOTE The microphone will perform best if it is worn as shown in Figure 3 1 Handling Precautions To avoid damage to circuits observe the following handling shipping and servicing precautions February 1997 68P02948C90 O Figure 3 1 Ideal Microphone Position Prior to and while servicing a remote speaker microphone particularly after moving within the service area momentarily place both hands on a bare metal earth grounded surface This will discharge any static charge which may have accumulated on the person doing the service Wherever possible avoid touching any electri cally conductive part of the unit with your hands NOTE Wearing a conductive wrist strap Motor ola No RSX 4015A will minimize static buildup during servicing WARNING While wearing a conductive wrist strap be careful near high voltage sources The good ground provided by the wrist strap will also increase the danger of lethal shock from accidentally touching high voltage sources When servicing a unit avoid carpeted areas dry environments and certain types of clothing silk nylon etc because they contribute to static buildup 3 1 Accessory Maintenance All electrically powered test equipment should be grounded Apply the ground lead from the test equipment to the unit before connecting the test probe Similarly disconnect the test probe prior to removing t
34. o normal operation described in the table below Exiting Test Mode To exit Test Mode proceed as follows e Turn radio off Turn RIB on e Turn radio on Table 5 3 Fail Mode Error number Failure Description Display Critical Tone Sound 1 Internal RAM Fatal 01 Yes Illegal tone 2 External RAM Fatal 02 Yes Illegal tone Reserved Reserved 5 Flash checksum Fatal 05 Yes Illegal tone 6 Codeplug checksum Error 06 Yes Illegal tone 7 1 Codeplug personality Error 06 No Illegal Tone when selected personality has checksum error Codeplug tuning error Error 06 Illegal tone 1 For error no 7 personality system change is allowed although the illegal tone is heard For error no 8 the tem porary illegal tone is heard See the Quick Start card for instructions on how to change personality To exit fail mode power radio off 5 2 68P02948C90 O February 1997 GTX GTX LTRLTS 2000 Portable Radios Service Manual Performance Checks Performance Checks Table 5 4 Transmitter Performance Checks COMMUNICATION ANALYZER TEST SET COMMENTS Reference Frequency Mode PWR MON 2nd channel test frequency Monitor Frequency error input at RF In Out TEST MODE Display 2 0 PTT to continuous during the performance check Frequency error to be lt 700 Hz Power RF Same as Above TEST MODE Display 2 0 Same as Above Refer to Maintenance Specification
35. oper low speed data deviation and select the PL or DPL filters The microprocessor then generates a square wave from U705 P6 which strobes the ASFIC PL_CLK U701 C3 For encode input at twelve times the desired data rate For example for a PL frequency of 103 Hz the frequency of the square wave at U701 P20 would be a1236 Hz This derives a tone generator inside U701 which generates a staircase approxima tion to a PL sine wave or DPL data pattern This inter nal waveform is then low pass filtered and summed with voice or data The resulting summed waveform then appears on U701 H8 VCO_ATN where it is sent to the transceiver board as previously described for transmit audio High Speed Data High speed data refers to the 3600 baud data wave forms ISWS AND OSWS used in a trunking system for high speed communication between the radio and the central controller To generate an ISW the micro processor U709 first programs the ASFIC U701 to the proper filter and gain settings It then begins strob ing U701 G1 Trunking Clock In with a square wave from U709 P5 at the same baud rate as the data The output waveform from 5 3 2 State Encoder of U701 is then fed to the post limiter summer block and then the splatter filter From that point it is routed through the mode attenuator and then out of the ASFIC to the transceiver board via VCO_ATN U701 H 8 DTMF Data DTMF data is a dual tone waveform used during phone interconnect o
36. peration They are divided into low group and high group tones The high group tone is generated by U709 P5 strobing U701 G1 at six times the tone frequency for tones less than 1440 Hz or twice the frequency for tones greater than 1440 Hz The low group tone is generated by U709 P7 strobing U701 G2 DTMF Clock at six times the tone frequency Inside U701 the low group and high group tones are summed with the amplitude of the high group tone being February 1997 TheorpO peration Controller approximately 2dB greater than that of the low group tone and then pre emphasized before being routed to the summer and splatter filter The waveform then follows the same path as was described for high speed data MDC Data The MDC signal follows exactly the same path as the DTMF high group tone MDC data utilizes MSK mod ulation in which a logic zero is represented by one cycle of a 1200 Hz sine wave and a logic one is 1 5 cycles of an 1800 Hz sine wave To generate the data the microprocessor U709 first programs the ASFIC U701 to the proper filter and gain settings It then begins strobing U701 G1 with a square wave from U709 P5 at the same baud rate as the data The output waveform from 0701 is fed to the post limiter summer block and then the splatter filter From that point it is routed through the mode attenuator and then out of ASFIC to the transceiver board via VCO_ATN 0701 H8 RX Audio Processing and Digital Volum
37. r Board DAC IC U400 with select line U709 P26 The LCD Driver uses the master out slave in MOSI line to send data to the display driver IC and the mas ter in slave out MISO line to send data back to the microprocessor U709 Note however that the key pad or any other SPI device can never initiate display data the microprocessor is at all times the SPI master device Thus the MOSI line and MISO line are always in the master configuration LED Control The bicolor LED located on the top of the radio is indi rectly activated by SPI of U709 via the DAC IC U400 on Transceiver Board When either input to the dual NPN transistor U410 is at logic high the correspond ing output pin pin 6 for the green LED pin 3 for the red should be at approximately 4 3 Vdc Note that it is possible to have both LED outputs on simultaneously in which case the LED emits a yellow orange light Audio amp Data Circuitry The transmit and receive audio paths are disabled in the standby mode and selectively enabled by the 2 6 68P02948C90 O GTX GTX LTR LTS 2000 Portable Radios Service Manual microprocessor when the radio transmits or receives a signal Also there are minor differences in the func tioning of both paths depending on whether an inter nal or external accessory microphone speaker is being used The radio constantly monitors the received data path for control channel data in trunking opera tion or sub audible data in conv
38. rence divider input from the 16 8 MHz tem perature compensated reference oscillator If the two frequencies differ the synthesizer generates a control error voltage causing the VCO to change frequency Modulation of the carrier is achieved by using a 2 port modulation technique The deviation of the low fre quency tone such as PL DPL is achieved by injecting the signal into an analog digital circuit in the synthe sizer The resulting digitized signal is then modulated by the fractional N divider this generates the required deviation The deviation of the high frequency tone is achieved by modulating the modulation varactor on the VCO To cover a very wide bandwidth the VCO control voltage is stepped up by using a positive mul tiplier circuit A 13 V supply powers the phase detector circuitry The VCO signal is amplified by the integrated buffer amplifier of the VCO buffer The buffer IC Tx output signal is filtered and channeled to the RF PA U101 The buffer IC Rx output signal is connected to the Rx injection buffer The output signal of that buffer is supplied to the receiver first mixer U50 as the injec tion signal Controller The GTX GTX LTR LTS 2000 controller is an open architecture which consists of U709 Motorola 68HC11K1 microprocessor U701 Audio Signalling Filter Integrated Circuit ASFIC U703 1 Kbyte EEPROM U705 128 256 Kbyte OTP FLASH ROM 0706 8 32 Kbyte Static RAM U707 LCD Displ
39. t frequency BW to narrow Conventional coded squelch personality Same as Above Deviation 800 MHz 2500 Hz but lt 1000 Hz 900 MHz 2250 Hz but lt 500 Hz Talk around Modulation radios with conventional talk around operation only February 1997 Change frequency to conventional talk around frequency Mode PWR MON deviation attenuation to 70 input to RF In Out Monitor DVM AC volts Set 1kHz Mod Out level for 25mVrms at test set Conventional talk around personality 68P02948C90 O Same as Above Deviation 800 MHz 23 8 kHz but lt 5 0 kHz 900 MHz 21 9 kHz but lt 2 45 kHz 5 3 Radio Diagnostic Utilities GTX GTX LTRLTS 2000 Portable Radios Service Manual Performance Checks Table 5 5 Receiver Performance Checks COMMUNICATION ANALYZER TEST SET COMMENTS Rated Audio Mode GEN Output level 1 0mV RF 1st Channel test frequency Mod 1 kHz tone at 3 kHz deviation Monitor DVM AC Volts TEST MODE Channel 0 Modulation Type 1 PTT to OFF center meter to Audio PA Set volume control to 2 84 Vrms Distortion Same as above except for distortion Same as Above Same as Above Distortion lt 5 0 Sensitivity SINAD Same as above except SINAD lower the rf level for 12 dB SINAD Same as Above PTT to OFF center RF input to be lt 0 35 uV Noise Squelch Threshold only radios with conventional system need
40. than 55 dBc To optimize the transmitter and receiver performance into the antenna a network is used to match the antenna s impedance to the harmonic filter The net work is made up of C125 and L122 The power control circuit consists of the networks associated with U151 Q151 Q155 and U111 0111 is a directional coupler which detects the forward power of the power module U101 The couple has 21 dB 1 dB coupling at port 2 The RF voltage at the cou pler port 2 is rectified by CR111 C111 R114 C112 and is applied to U151A This signal is amplified by U151A and applied to summing and integrator amplifier U151B POSITIVE MULTIPLIER GTX GTX LTR LTS 2000 Portable Radios Service Manual The voltage at the second input of the summing amp is supplied by DAC U400 P9 This DAC is controlled by the microprocessor and provides the reference voltage for the control loop The error voltage at the input of U151B 13 produces a voltage at its output which is in turn applied to the drivers Q151 Q152 The voltage from Q151 collector is applied to the controlled stage of the power module Frequency Generation Unit The Frequency Generation Unit FGU consists of the following major sections the high stability reference oscillator U210 fractional N synthesizer U220 VCO U260 VCO buffer IC U270 and Rx injection buffer Q280 Q281 and the surrounding components The VCO provides the carrier frequency for the transmitt
41. tuting parts General Parts Replacement and Substitution Special care should be taken to be as certain as possible that a suspected component is actually the one at fault This special care will eliminate unnecessary unsoldering and removal of parts which could damage or weaken other components or the printed circuit board itself When damaged parts are replaced identical parts should be used If the identical replacement component is not locally available check the parts list for the proper Motorola part number and order the component from the nearest Motorola Communications Parts office listed in the Replacement Parts Ordering section of this manual Rigid Circuit Boards This family of radios uses bonded multi layer printed circuit boards Since the inner layers are not accessible some special considerations are required when soldering and unsoldering components The printed through holes may interconnect multiple layers of the printed circuit Therefore care should be exercised to avoid pulling the plated circuit out of the hole When soldering near the 28 pin connector use care to avoid accidentally getting solder in the connector Also be careful not to form solder bridges between the connector pins Closely examine your work for shorts due to solder bridges Chip Components Use either the RLN4062 Hot Air Repair Station or the Motorola 0180381B45 Repair Station for chip component replacement When using th
42. whenever a periodic visual inspection reveals the presence of smudges grease and or grime Internal surfaces should be cleaned only when the radio is disassembled for servicing or repair The only recommended agent for cleaning the external radio surfaces is a 0 5 solution of a mild dishwashing detergent such as Joye in water The only factory recommended liquid for cleaning the printed circuit boards and their components is isopropyl alcohol 70 by volume February 1997 CAUTION The effects of certain chemicals and their vapors have harmful results on certain plastics Aerosol sprays tuner cleaners and other chemicals should be avoided Cleaning External Plastic Surfaces The detergent water solution should be applied sparingly with a stiff non metallic short bristled brush to work all loose dirt away from the radio A soft absorbent lintless cloth or tissue should be used to remove the solution and dry the radio Make sure that no water remains entrapped near the connectors cracks or crevices Cleaning Internal Circuit Boards and Components Isopropyl alcohol may be applied with a stiff non metallic short bristled brush to dislodge embedded or caked materials located in hard to reach areas The brush stroke should direct the dislodged material out and away from the inside of the radio Alcohol is a high wetting liquid and can carry contamination into unwanted places if an excessive quantity is used Make sure t
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