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Motorola GP320 Service Information

Vhf (136-174mhz).
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Professional Radio
GP Series
VHF (136-174MHz)
Service Information
Issue: June 2002



   Also See for Motorola GP320

   Summary of Contents for Motorola GP320

  • Page 1

    Professional Radio GP Series VHF (136-174MHz) Service Information Issue: June 2002...

  • Page 2: Computer Software Copyrights

    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...

  • Page 3: Table Of Contents

    Table of Contents Chapter 1 MODEL CHART AND TECHNICAL SPECIFICATIONS 1.0 GP320/GP340/GP360/GP380 Model Chart............1-1 2.0 GP140 Model Chart .....................1-2 3.0 GP640/GP680 Model Chart .................1-2 4.0 GP1280 Model Chart ...................1-3 5.0 GP240/GP280/GP540/GP580 Model Chart............1-4 6.0 Technical Specifications ..................1-5 Chapter 2 THEORY OF OPERATION 1.0 Introduction ......................2-1...

  • Page 4

    Chapter 4 VHF PCB/SCHEMATICS/PARTS LISTS 1.0 Allocation of Schematics and Circuit Boards ............4-1 1.1 Controller Circuits ................... 4-1 1.2 Voice Storage Facility..................4-1 2.0 VHF PCB 8486062B12 / Schematics ..............4-3 3.0 VHF PCB 8486062B12 Parts List ..............4-11 4.0 VHF PCB 8486101B09 / Schematics (GP1280)..........

  • Page 5: Gp320/gp340/gp360/gp380 Model Chart

    Chapter 1 MODEL CHART AND TECHNICAL SPECIFICATIONS GP320/GP340/GP360/GP380 Model Chart Professional GP300 Series (VHF) Model Description MDH25KDC9AN0_E GP320 VHF 136-174MHz 5W 1-Ch MDH25KDC9AN3_E GP340 VHF 136-174MHz 5W 16-Ch MDH25KDF9AN5_E GP360 VHF 136-174MHz 5W 255-Ch MDH25KDH9AN6_E GP380 VHF 136-174MHz 5W 255-Ch...

  • Page 6: Gp140 Model Chart

    MODEL CHART AND TECHNICAL SPECIFICATIONS GP140 Model Chart Professional GP140 (VHF) Model Description MDH25KDC9AA3_E GP140 VHF 136-174 MHz 5W 16 Ch Item Description PMLE4109_ *GP140 UHF Back Cover Kit 6864110B25 GP140 Basic User Guide PMAD4023_ VHF 14cm (150-161 MHz) Antenna HNN9008_ Battery, NiMH Standard x = Indicates one of each is required.

  • Page 7: Gp1280 Model Chart

    GP1280 Model Chart GP1280 Model Chart Professional GP1280 (VHF) Model Description MDH25KDN9CK8_E GP1280 VHF 136-174 MHz 5W Item Description PMLD4120_ *GP1280 VHF Back Cover Kit 6864110B20 GP1280 Basic User Guide PMAD4023_ VHF 14cm (150-161 MHz) Antenna HNN9008_ Battery, NiMH Standard x = Indicates one of each is required.

  • Page 8

    MODEL CHART AND TECHNICAL SPECIFICATIONS GP240/GP540/GP280/GP580 Model Chart Professional GP200/GP500 Series (VHF) Model Description MDH25KDC9GC3 GP540 VHF 136-174MHz 5W MDH25KDH9GC6 GP580 VHF 136-174MHz 5W MDH25KDC9GB3 GP240 VHF 136-174MHz 5W MDH25KDH9GB6 GP280 VHF 136-174MHz 5W Item Description *PMLD4170_ GP240/GP540 VHF Back Cover Kit *PMLD4171_ GP280/GP580 VHF Back Cover Kit *PMLD4216_...

  • Page 9: Technical Specifications

    Technical Specifications Technical Specifications Data is specified for +25°C unless otherwise stated. General Specifications Channel Capacity GP140 GP240, GP280 128 in conventional Mode GP320 GP340 GP360, GP380 GP540, GP580 128 in conventional Mode GP640, GP680, GP1280 16 (Conventional) Power Supply Rechargeable battery 7.5v...

  • Page 10

    MODEL CHART AND TECHNICAL SPECIFICATIONS Transmitter 136-174 *Frequencies - Full Bandsplit Channel Spacing 12.5/20/25 kHz Frequency Stability ±2.5 ppm (-25°C to +55°C, +25° Ref.) Power 136 - 174 MHz:1-5W ±2.5 @ 12.5 kHz Modulation Limiting ±4.0 @ 20 kHz ±5.0 @ 25 kHz FM Hum &...

  • Page 11: Introduction

    Chapter 2 THEORY OF OPERATION Introduction This Chapter provides a detailed theory of operation for the VHF 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.

  • Page 12: Antenna Switch

    THEORY OF OPERATION The LDMOS PA is capable of supplying an output power of 7W with an input signal of 0.3W. The current drain is typically around 1800mA while operating in the frequency range of 136-174MHz. The power output is varied by changing the bias voltage. Antenna Switch The antenna switch circuit consists of two pin diodes, D3521 and D3551, a pi network (C3531, L3551 and C3550), and three current limiting resistors (R3571, R3572, R3573).

  • Page 13: Vhf Receiver

    VHF Receiver VHF Receiver The VHF receiver consists of a front end, back end, and automatic gain control circuits. A block diagram of the VHF receiver is shown in Figure 2-2. Detailed descriptions of these features are contained in the paragraphs that follow. Antenna Pin Diode Varactor...

  • Page 14: Receiver Back-end

    THEORY OF OPERATION Both the pre and post-RF amplifier varactor tuned filters have similar responses. The 3 dB bandwidth of the filter is about 12 MHz. This enables the filters to be electronically controlled by using a single control voltage which is DACRx. The output of the post-RF amplifier filter is connected to the passive double balanced mixer which consists of T3301, T3302, and CR3301.

  • Page 15: Automatic Gain Control (agc)

    VHF Receiver Automatic Gain Control (AGC) (Refer to the Receiver Front End and Receiver Back End schematic diagrams) The front end automatic gain control circuit provides automatic reduction of gain of the front end RF amplifier via feedback. This prevents overloading of backend circuits and is achieved by drawing some of the output power from the RF amplifier output.

  • Page 16: Frequency Generation Circuit

    THEORY OF OPERATION Frequency Generation Circuit (Refer to Figure 2-3 and the VHF Frequency Synthesizer schematic diagram) The Frequency Generation Circuit, shown in Figure 2-3, is composed of two main ICs, the Fractional-N synthesizer (U3701), and the VCO/Buffer IC (U3801). Designed in conjunction to maximize compatibility, the two ICs provide many of the functions that normally would require additional circuits.

  • Page 17: Synthesizer

    Frequency Generation Circuit Synthesizer The Fractional-N Synthesizer, shown in Figure 2-4, uses a 16.8MHz crystal (Y3761) to provide a reference for the system. The LVFractN IC (U3701) further divides this to 2.1MHz, 2.225MHz, and 2.4MHz as reference frequencies. Together with C3761, C3762, C3763, R3761, and D3761, they build up the reference oscillator that is capable of 2.5 ppm stability over temperatures of -30 to 85°C.

  • Page 18: Voltage Controlled Oscillator (vco)

    THEORY OF OPERATION Voltage Controlled Oscillator (VCO) (Refer to Figure 2-4 and the VHF Voltage Controlled Oscillator schematic diagram) The VCOB IC (U3801), shown in Figure 2-5, in conjunction with the Fractional-N synthesizer (U3701) generates RF in both the receive and the transmit modes of operation. The TRB line (U3801 pin 19) determines which oscillator and buffer are enabled.

  • Page 19

    Frequency Generation Circuit Table 2-1 Level Shifter Logic Desired AUX 4 AUX 3 Mode n.u. High (@3.2V) High (@3.2V) n.u. Battery Saver n.u. Hi-Z/Float Hi-Z/Float (@1.6V) (@1.6V) In the receive mode, U3801 pin 19 is low or grounded. This activates the receive VCO by enabling the receive oscillator and the receive buffer of U3801.

  • Page 20: Voice Storage (gp1280)

    2-10 THEORY OF OPERATION Voice Storage (GP1280) (Refer to Figure 2-6 and the VHF Voice Storage schematic diagram) The Voice Storage feature is offered as standard in the GP1280 and as an Option board for GP340/GP360/GP380 and GP640/GP680. The Voice Storage feature enables users to: Record and Playback Personal Memo (Reminders, Notes, etc.).

  • Page 21

    Voice Storage (GP1280) 2-11 Audio routing to the Voice Storage circuitry during receive message recording, message playback, personal memo recording and voice prompt transmit over the air are as follows: Received Message Recording The receive audio is tapped from the Rx_Aud_Rtn pin of the ASFIC_CMP during receive mode. Message Playback Message playback is via the FLAT_RX_SND pin of ASFIC_CMP.

  • Page 22


  • Page 23: Troubleshooting Flow Chart For Receiver (sheet 1 Of 2)

    Chapter 3 TROUBLESHOOTING CHARTS Troubleshooting Flow Chart for Receiver (Sheet 1 of 2) START Bad SINAD Bad 20dB Quieting No Recovered Audio udio Check Controller at pin 27 of U3220? Spray of inject 1st IF into XTAL Filter IF Freq: 45.1MHz Check Q3270 bias circuitry for faults.

  • Page 24: Troubleshooting Flow Chart For Receiver (sheet 2 Of 2)

    TROUBLESHOOTING CHARTS Troubleshooting Flow Chart for Receiver (Sheet 2 of 2) Inject RF into J3501 Q3200 Trace IF signal collector OK? IF Signal from C3200 to IF signal at C3200? Q3200. Check for present? bad XTAL filter. Before replacing U3220, check U3220 voltages;...

  • Page 25: Troubleshooting Flow Chart For Transmitter

    Troubleshooting Flow Chart for Transmitter Troubleshooting Flow Chart for Transmitter START No Power There B+ Bias for Check Q3561 Ant switch D3521 Control Voltage High Check PCIC Current or Low at TP3502 High 1. Check Pin Diodes Check Drive to 2.

  • Page 26: Troubleshooting Flow Chart For Synthesizer

    TROUBLESHOOTING CHARTS Troubleshooting Flow Chart for Synthesizer 3.3V Start at U3701 Check pins 5, 20, U3201, 34 & 36 L3731 Visual Check D3701, Correct check of the D3702, U3701, Problem Board C3701 - C3707 Is U3701 16.8MHz 16.8MHz at pin 6 of Replace Pin47 AT = 13 signal at...

  • Page 27: Troubleshooting Flow Chart For Vco

    Troubleshooting Flow Chart for VCO Troubleshooting Flow Chart for VCO START No LO? Check R3811 U3801 for dry joint Carrier? Pin 10 TRB = 3.2V or faulty >1V? VCO OK L3831, Change L3831, L3832 L3832 L3833 O/C? AUX 3 at Check U3701 R3829...

  • Page 28


  • Page 29: Allocation Of Schematics And Circuit Boards

    Chapter 4 VHF PCB/SCHEMATICS/PARTS LISTS Allocation of Schematics and Circuit Boards Controller Circuits The VHF circuits are contained on the printed circuit board (PCB) which also contains the Controller circuits. This Chapter shows the schematics for the VHF circuits only, refer to the Controller section for details of the related Controller circuits .

  • Page 30

    VHF PCB/SCHEMATICS/PARTS LISTS Table 4-2 VHF GP1280 Diagrams and Parts Lists PCB : 8486101B09 Main Board Top Side Page 4-15 8486101B09 Main Board Bottom Side Page 4-16 8486101B10 Main Board Top Side Page 4-29 8486101B10 Main Board Bottom Side Page 4-30 SCHEMATICS Controls and Switches Page 4-5...

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