ASTRO Digital XTL 1500 Mobile Radio Detailed Service Manual

Manufacturer: Motorola, Inc.

Document Number: 6815854H01-A

Publication Date: June 2005

Foreword

This manual provides information for qualified service technicians to troubleshoot and repair ASTRO Digital XTL 1500 mobile radios (VHF/UHF Range 1/UHF Range 2/700-800 MHz) equipped with XTL 1500 control heads. It enables component-level repair. For radio operation and basic troubleshooting, refer to applicable separate manuals. Manual revisions are provided via FMRs (Florida Manual Revisions).

Product Safety and RF Exposure Compliance

CAUTION: Read operating instructions for safe usage in the enclosed Product Safety and RF Exposure booklet.

ATTENTION: This radio is restricted to occupational use to satisfy FCC RF energy exposure requirements. Read RF energy awareness information and operating instructions in the enclosed booklet (Motorola Publication part number 6881095C99) for compliance.

Introduction

This manual details the ASTRO Digital XTL 1500 mobile radio, a dual-mode (trunked/conventional) transceiver incorporating a Digital Signal Processor (DSP). It supports analog and ASTRO digital modes across VHF (136-174 MHz), UHF Range 1 (380-470 MHz), UHF Range 2 (450-520 MHz), and 700/800 MHz bands.

Notations Used:

DANGER: Imminent hazard, will result in death or injury if not avoided.
WARNING: Potentially hazardous situation, could result in death or injury if not avoided.
CAUTION: Potentially hazardous situation, might result in equipment damage if not avoided.
NOTE: Essential operational procedure or condition to emphasize.

This manual, along with the Basic Service Manual (6815853H01), aids in troubleshooting to board and component levels.

Product Overview

The ASTRO Digital XTL 1500 radio is a wideband, synthesized, dual-mode transceiver supporting analog and ASTRO digital operation. It is available in VHF, UHF Range 1, UHF Range 2, and 700/800 MHz bands.

Functional Blocks

Key functional blocks include:

Control-Head Assembly: Controller, Power Management, User Interface, Vehicle Interface Ports (VIPs).
Radio Power Distribution.
Receiver Front-End: Preselector, LNA, Mixer.
Receiver Back-End: IF amplifier/filter, Digital receiver IC (ABACUS III).
Transmitter: RF Power Amplifier (RFPA), Output Network, Power Control.
Frequency Generation Unit: Synthesizer, VCOs, reference oscillator.
Controller Section: Microprocessor, DSP, vocoder.

Control-Head Assembly

The control head houses the user interface and primary control logic. It includes:

Controller: OMAP Applications Processor, Flash memory, SDRAM for radio control and display management.
Power Management: ATTiny13 microcontroller for power state control, and voltage regulators for various power levels.
User Interface: STN LCD display, keypad, volume/frequency knobs.
Vehicle Interface Ports (VIPs): Allow activation of external circuits (e.g., horn relay, light relay).

Receiver Section

The receiver section, differing slightly by band (VHF, UHF, 700/800 MHz), comprises a front-end (filters, LNAs, mixer) for signal reception and optimization, and a back-end (IF filters, ABACUS III IC) for signal digitization and processing.

Transmitter Section

The transmitter section includes an RF Power Amplifier (RFPA), Output Network (antenna switch, harmonic filter, power detector), and Power Control circuitry to amplify and transmit signals across the specified frequency bands.

Frequency Generation Unit (FGU)

The FGU generates necessary local oscillator (LO) signals using synthesizers, voltage-controlled oscillators (VCOs), and reference oscillators, enabling frequency tuning for both receive and transmit operations across all bands.

Controller Section

The controller section manages radio operations in both Analog and Digital (ASTRO) modes. It includes the microprocessor, DSP, memory (Flash, SRAM), and interfaces for communication, audio processing, and power control.

Theory of Operation

This section details the internal workings of the control head and main boards.

Control Head Board

Controller: Features an OMAP processor, Flash ROM for firmware, and SDRAM for scratchpad memory. It interfaces with peripherals via SPI, I2C, and GPIO.

Power Management: An ATTiny13 microcontroller manages power-up, power-down, and reset sequences. Multiple voltage regulators supply power to various components. The power distribution ensures correct voltage levels for the OMAP processor, memory, and other circuits.

User Interface: Includes an LCD display driven by a Solomon SSD1805 driver, a keypad, and rotary knobs for volume and frequency selection, all managed by the OMAP processor.

GCAI Accessory Interface: Supports Motorola's Global Core Accessory Interface standard, enabling compatibility with various accessories via USB, RS232 UART, and GPIOs.

Main Board

The main board houses the radio's core RF and processing components, divided into sections based on frequency band:

Radio Power Distribution: Manages DC power from the vehicle battery or external supply, distributing regulated voltages (e.g., 13.8V, 9.3V, 5V, 3.0V, 2.85V, 1.85V, 1.55V) to various sections.
Receiver Front-End (RXFE): Optimizes signal reception through filters, Low-Noise Amplifiers (LNAs), and mixers. Specific filter and LNA configurations vary by frequency band (VHF, UHF, 700/800 MHz) to manage selectivity and sensitivity.
Receiver Back-End (RXBE): Processes the IF signal using crystal filters and the ABACUS III IC (AD9874) for digitization, filtering, and baseband signal generation.
Transmitter: Comprises the RF Power Amplifier (RFPA), Output Network (antenna switch, harmonic filter), and Power Control circuitry to amplify and regulate transmit power.
Frequency Generation Unit (FGU): Generates local oscillator (LO) signals using synthesizers and VCOs, essential for tuning to desired receive and transmit frequencies.
Controller Section: Contains the Patriot microprocessor, memory, and interfaces for managing radio functions, communication protocols (RS-232, USB, SB9600), and audio processing.

Troubleshooting Procedures

This chapter outlines procedures for diagnosing and resolving radio issues. It covers handling precautions for sensitive components, voltage measurements, signal tracing, and interpreting power-up self-check error codes and operational error codes. Band-specific troubleshooting guidance is provided for VHF, UHF Range 1, UHF Range 2, and 700/800 MHz main boards, addressing common faults like VCO unlock, low output power, and receiver sensitivity issues.

Related Publications

Additional Motorola manuals relevant to the ASTRO Digital XTL 1500 include:

ASTRO Digital XTL 1500 Mobile Radio Installation Manual (6815851H01)
ASTRO Digital XTL 1500 VHF/UHF Range 1/UHF Range 2/700-800 MHz Mobile Radio Basic Service Manual (6815853H01)
CPS Programming Installation Guide (6881095C44)
System 9000 Direct Entry Keyboard Instruction Manual (68P80101W22-B)

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