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3-2

Low Band TROUBLESHOOTING CHARTS

2.0

Troubleshooting Flow Chart for Receiver

(Sheet 1 of 2)

Audio

at pin 8 of

U1103

?

Audio
heard

?

Check

voltages on

U1103.

OK?

Bad SINAD

Bad 20dB Quieting

No Recovered Audio

START

Check Controller (in the case of no audio).

Or else go to “B”

Yes

No

Spray or inject 10.7MHz

into XTAL Filter FL1102.

B

Yes

No

Check 2nd LO

(10.245MHz) at C1129.

LO

present

B

Yes

Biasing

OK

No

No

A

Yes

Check Q1106 bias

for faults.

Replace Q1106.

Go to B

Yes

No

Check

circuitry

around

U1103.

Replace

U1103 if

defect.

Check circuitry around Y1101.

Replace Y1101 if defect.

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Содержание LB1 (29.6 - 36.0MHz)

Страница 1: ...Professional Radio GM Series LB1 29 6 36 0MHz LB2 36 0 42 0MHz LB3 42 0 50 0MHz Service Information Issue August 2002 ...

Страница 2: ...he copyrighted computer program Accordingly any copyrighted Motorola computer programs contained in the Motorola products described in this manual may not be copied or reproduced in any manner without the express written permission of Motorola Furthermore the purchase of Motorola products shall not be deemed to grant either directly or by implication estoppel or otherwise any license under the cop...

Страница 3: ...0 Low Band Transmitter Power Amplifier PA 25 60 W 2 5 3 1 Power Controlled Stage 2 5 3 2 Driver Stage 2 5 3 3 Final Stage 2 6 3 4 Antenna Switch 2 6 3 5 Harmonic Filter 2 6 3 6 Power Control 2 6 3 7 TX Safety Switch 2 6 4 0 Low Band Frequency Synthesis 2 7 4 1 Fractional N Synthesizer 2 7 4 2 Voltage Controlled Oscillator VCO 2 9 4 3 Synthesizer Operation 2 10 Chapter 3 TROUBLESHOOTING CHARTS 1 0 ...

Страница 4: ...8486207B05 Schematics 4 18 3 1 LB2 25 60W PCB 8486207B05 Parts List 4 28 4 0 LB3 25 60W PCB 8485908z03 Schematics 4 31 4 1 LB3 25 60W PCB 8485908z03 Parts List 4 41 5 0 LB1 25 60W PCB 8486206B08 Schematics 4 44 5 1 LB1 25 60W PCB 8486206B08 Parts List 4 48 6 0 LB2 25 60W PCB 8486207B07 Schematics 4 51 6 1 LB2 25 60W PCB 8486207B07 Parts List 4 53 7 0 LB3 25 60W PCB 8485908z04 Schematics 4 56 7 1 L...

Страница 5: ...Replaceable Unit Main Board GM360 X X X ENBN4056_ Packaging Waris Mobile X X X HKN9402_ 12V Power Cable X X X MDRMN4025_ Enhanced Compact Microphone X X X RLN4774_ 3 Point Mount X X X 6864110B81_ User Guide GM360 X Indicates one of each is required General Specifications Channel Capacity GM360 255 Power Supply 13 2Vdc 10 8 15 6Vdc Dimensions H x W x D mm Height excluding knobs GM360 59mm x 179mm x...

Страница 6: ...mum Deviation 3 typical 3 typical 3 typical Receiver LB1 LB2 LB3 Frequencies Full Bandsplit LB1 29 7 36 0 MHz LB2 36 0 42 0 MHz LB2 42 0 50 0 MHz Channel Spacing 12 5 20 25 kHz 12 5 20 25 kHz 12 5 20 25 kHz Sensitivity 12 dB SINAD 0 30 µV 0 22 µV typical 0 30 µV 0 22 µV typical 0 30 µV 0 22 µV typical Intermodulation ETS 65 dB 65 dB 65 dB Adjacent Channel Selectivity ETS 65 dB 12 5 kHz 75 dB 20 kH...

Страница 7: ...ion This Chapter provides a detailed theory of operation for the LowBand circuits in the radio For details of the theory of operation and trouble shooting for the the associated Controller circuits refer to the Controller Section of this manual ...

Страница 8: ...r noise blanker Two fixed tuned bandpass filters perform antenna signal pre selection A cross over quad diode mixer converts the signal to the high IF of 10 7 MHz High side first injection is used Figure 2 1 Low Band Receiver Block Diagram Demodulator Delay Filter Mixer Fixed Tuned Filter RF Amp Tuned Filter Pin Diode Antenna Switch RF Jack Antenna First LO RXINJ Recovered Audio RSSI IF Second LO ...

Страница 9: ...ts passband for best half IF attenuation 2 3 First Mixer The signal coming from the front end is converted to the high IF frequency of 10 7 MHz using a cross over quad diode mixer U1051 The high side injection signal RXINJ from the frequency synthesizer circuitry is filtered by a 7 pole low pass filter L1012 14 and associated circuitry which removes second harmonic content from the injection signa...

Страница 10: ...is fed to the ASFIC_CMP U0221 pin 2 part of the Controller circuitry A received signal strength indicator RSSI signal is available at U1103 pin 5 having a dynamic range of 70 dB The RSSI signal is interpreted by the microprocessor U0101 pin 63 and in addition is available at accessory connector J0501 15 2 6 Extender Noise Blanker The 10 7 MHz output from the first mixer which is present at the inp...

Страница 11: ...plied to pin 1 from the power control circuit U1503 pin 4 with transistors Q1504 5 providing current gain and level shifting The control voltage simultaneously varies the bias of two FET stages within U1401 This biasing point determines the overall gain of U1401 and therefore its output drive level to Q1401 which in turn controls the output power of the PA 3 2 Driver Stage The next stage is an LDM...

Страница 12: ...ance D1401 allows the RF output from final stages Q1402 and Q1403 to be applied to the input of the low pass harmonic filter L1421 3 and associated components D1402 appears as a short circuit at the input of the receiver RXINJ preventing transmitter RF power from entering the receiver L1420 and C1456 appear as a broadband _ wave transmission line making the short circuit presented by D1402 appear ...

Страница 13: ...y characteristic to minimize splatter into adjacent channels U1501 is a temperature sensing device which monitors the circuit board temperature in the vicinity of the transmitter circuits and provides a dc voltage to the PCIC TEMP pin 29 proportional to temperature If the DC voltage produced exceeds the set threshold in the PCIC the transmitter output power will be reduced so as to reduce the tran...

Страница 14: ... the synthesizer loop A high level at this output indicates a stable loop A buffered output of the 16 8 MHz reference frequency is provided at pin 19 The operating frequency of the synthesizer is loaded serially from the microprocessor via the data line DATA U1201 7 clock line CLK U1201 8 and chip select line CSX U1201 9 The reference oscillator circuit within U1201 uses an external 16 8 MHz cryst...

Страница 15: ...ctive when RF is applied to their inputs The RF signal at the bases of the second buffers are combined and fed back to the Fractional N synthesizer via PRE_IN where it is compared to the reference frequency as described below in Synthesizer Operation The Fractional N IC provides a DC steering voltage VCTRL to adjust and maintain the VCO at the correct frequency With a steering voltage from 2 5V to...

Страница 16: ...tector is a pulsed DC signal which is routed to the charge pump The charge pump outputs a current at pin 43 of U1201 I OUT The loop filter which consists of R1205 6 R1208 C1212 14 transforms this current into a voltage that is applied to the varactor diodes CR1310 for transmit CR1302 for receive and alters the output frequency of the appropriate VCO The current can be set to a value fixed in the L...

Страница 17: ... of Q1402 Q1403 Check circuitry between Q1402 Q1403 and Antenna Port Check MOSBIAS_1 Supply and Feed Network No 18V pp Yes No Yes 1A No Check Q1401 Device Yes CURRENT RF Junction R1413 DC TP1402 TP1403 Yes Check MOSBIAS_2 MOSBIAS_3 and Feed Networks Check DC AC Gate Circuits of Q1402 Q1403 Check Supply Feed and or PowerControl Circuits No 18V pp Check U1401 Device AC Gate of Q1401 Voltage Yes DC U...

Страница 18: ...ng No Recovered Audio START Check Controller in the case of no audio Or else go to B Yes No Spray or inject 10 7MHz into XTAL Filter FL1102 B Yes No Check 2nd LO 10 245MHz at C1129 LO present B Yes Biasing OK No No A Yes Check Q1106 bias for faults Replace Q1106 Go to B Yes No Check circuitry around U1103 Replace U1103 if defect Check circuitry around Y1101 Replace Y1101 if defect ...

Страница 19: ... No No No or Check harmonic filters J1401 and ant switch Check preselector and RF amp Inject RF into J1401 No Yes Check RF amp Q1001 Stage Check filter between C1017 mixer U1051 Yes Yes 1st LO level OK Locked Yes Check FGU Yes Trace IF signal from C1036 to Q1106 Check for bad XTAL filter No Yes IF signal at Q1106 collector Before replacing U1103 check U1103 voltages Yes Check Supply Voltage circui...

Страница 20: ...8 Check C3319 Replace U1201 Remove Shorts Is there a short between Pin 47 and Pins 14 15 of U1201 Replace or resolder necessary components Are R1205 R1206 R1208 C1212 C1213 C1214 OK Replace U1201 If Q1202 Feedback Amp stage is OK Then see VCO troubleshooting chart Are Waveforms at Pins 14 15 triangular Do Pins 7 8 9 of U1201 toggle when channel is changed Check programming lines between U0101 and ...

Страница 21: ...ck parts between NO NO NO NO NO YES YES YES YES YES Low or NO RF Signal at Input to PA Visual Check of Board OK 8 5V DC at U1378 Pin 3 4 5V DC at U1377 Pin 2 8 5V DC at U1377 Pin 4 Is RF YES YES YES YES YES NO NO NO NO NO U1051 and Q1305 Q1305 Troubleshoot Buffer Stage Make sure U1377 and U1378 are working correctly Is RF Q1308 NO YES Check parts between U1401 and Q1308 RX VCO TX VCO at U1378 avai...

Страница 22: ...3 6 Low Band TROUBLESHOOTING CHARTS ...

Страница 23: ...Main Board Top Side 8486206B06 Main Board Bottom Side Page 4 5 Page 4 6 SCHEMATICS Power Amplifier 25 60W Sheet 1 of 2 Power Amplifier 25 60W Sheet 2 of 2 Voltage Controlled Oscillator Receiver Front End IF Sheet 1 of 2 IF Sheet 2 of 2 Noise Blanker FRACN Page 4 7 Page 4 8 Page 4 9 Page 4 10 Page 4 11 Page 4 12 Page 4 13 Page 4 14 Parts List 8486206B06 Page 4 15 Controller version is T6 Table 4 2 ...

Страница 24: ...4 34 Page 4 35 Page 4 36 Page 4 37 Page 4 38 Page 4 39 Page 4 40 Parts List 8485908z03 Page 4 41 Controller version is T9 Table 4 4 LB1 25 60W Diagrams and Parts Lists PCB 8486206B08 Main Board Top Side 8486206B08 Main Board Bottom Side Page 4 44 Page 4 45 SCHEMATICS Power Amplifier 25 60W Sheet 1 of 2 Power Amplifier 25 60W Sheet 2 of 2 Voltage Controlled Oscillator Receiver Front End IF Sheet 1 ...

Страница 25: ...e 4 21 Page 4 22 Page 4 23 Page 4 46 Page 4 47 Page 4 26 Page 4 27 Parts List 8486207B07 Page 4 53 Controller version is T11 Table 4 6 LB3 25 60W Diagrams and Parts Lists PCB 8485908z04 Main Board Top Side 8485908z04 Main Board Bottom Side Page 4 56 Page 4 57 SCHEMATICS Power Amplifier 25 60W Sheet 1 of 2 Power Amplifier 25 60W Sheet 2 of 2 Voltage Controlled Oscillator Receiver Front End IF Sheet...

Страница 26: ...4 4 Low band pcb schematics parts lists ...

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