Bose L1 Model II Service Manual

The Bose L1 Model II is a portable line array loudspeaker system designed for musicians and presenters. It features a modular design with a power stand containing amplifiers and controls, interchangeable array modules (B1 or B2 bass modules), and a telescoping column with multiple speaker elements. This service manual covers technical specifications, disassembly procedures, component replacement, troubleshooting, and safety information for qualified service personnel.

System Overview & Features

Key components: Power Stand (L1M2 Power Stand), Array Loudspeaker (T1 ToneMatch Audio Engine optional), Bass Module (B1 or B2), Telescoping Column.

Safety Precautions

Before servicing, disconnect AC power and allow internal capacitors to discharge.

1. Electrical Safety: Unit contains hazardous voltages. Service only by qualified personnel.
2. Discharge Capacitors: Wait at least 5 minutes after disconnecting power before opening chassis.
3. ESD Protection: Use anti-static wrist strap when handling circuit boards.
4. Lifting: Bass modules are heavy; use proper lifting technique or assistance.
5. Reassembly: Ensure all connectors are secure and no cables are pinched before closing chassis.

WARNING! Risk of electric shock. No user-serviceable parts inside. Refer servicing to qualified Bose service personnel.

Technical Specifications

• System Type: Portable line array loudspeaker system.
• Amplifier Power (Total): 550W (Power Stand with B2 Bass Module).
• Frequency Response: 39Hz - 16kHz (±3dB) with B2 module.
• Coverage Pattern: 180° horizontal, 40° vertical (array deployed).
• Maximum SPL: 121 dB at 1 meter (system peak).
• Inputs: 2 x XLR/TRS combo jacks (mic/line), 1 x 1/8" auxiliary input.
• Outputs: XLR link output, 1/8" headphone output.
• Power Requirements: 100-240V AC, 50/60Hz, 2.5A max.
• Dimensions (Power Stand): 7.5" H x 15.5" W x 15.5" D (19 x 39.4 x 39.4 cm).
• Weight: Power Stand: 24 lbs (10.9 kg); B2 Bass Module: 47 lbs (21.3 kg).

Exploded Views & Parts List

Refer to official Bose parts diagrams for exact part numbers. Major assemblies include:

Power Stand Assembly (P/N: #####): Main chassis, amplifier board, power supply board, cooling fan, input panel, transformer.

Array Column Assembly (P/N: #####): Telescoping sections (upper/lower), 24 driver elements, wiring harness, column base connector.

B2 Bass Module Assembly (P/N: #####): Enclosure, two 10" woofers, port tube, terminal cup, grille.

Replacement Parts: Drivers, fuses (T5A 250V), power cord, control knobs, feet, connectors.

Disassembly Instructions

Tools required: Phillips screwdrivers (#1, #2), Torx drivers (T10, T15), nut drivers, plastic pry tools.

1. Power Stand: Remove 10 screws from bottom panel. Lift top cover carefully, disconnecting internal ribbon cables.
2. Amplifier Module: Disconnect all wiring connectors. Remove 4 mounting screws to extract board.
3. Array Column: Extend column fully. Remove end caps and carefully separate upper/lower sections.
4. Driver Replacement: Remove grille clips. Unscrew driver mounting screws. Disconnect speaker wires.
5. Bass Module: Remove terminal cup screws. Detach cup and internal wiring. Remove woofer mounting screws from inside enclosure.

Tip: Take photos during disassembly to aid reassembly. Keep screws organized.

Component Testing & Replacement

Use multimeter for continuity and voltage tests.

1. Fuse Check: Locate fuse on power supply board. Test for continuity. Replace with exact same type (T5A 250V).
2. Power Supply Test: Check for +48V, +/-15V, and +5V DC outputs at test points on board.
3. Amplifier Output Test: With dummy load, inject test signal and check for clean output on oscilloscope.
4. Driver Test: Test each driver for DC resistance (should be approximately 6-8 ohms).
5. Cooling Fan: Check for 12V DC at fan connector. Replace if noisy or not spinning.

WARNING! Always replace components with genuine Bose parts to maintain performance and safety.

Amplifier Module Service

The Class-D amplifier module contains sensitive SMD components.

1. Visual Inspection: Check for burnt components, bulging capacitors, or cracked solder joints.
2. Thermal Paste: When remounting amplifier ICs, apply fresh thermal compound.
3. Connector Integrity: Ensure all edge connectors and ribbon cables are clean and seated firmly.
4. Firmware: Some issues may require firmware update via service port (requires Bose service software).
5. Module Replacement: If faulty, replace entire amplifier module as a unit (P/N: #####).

CAUTION! Electrostatic discharge can damage amplifier ICs. Use proper ESD precautions.

Array Column Service

Handling the column array requires care to avoid damaging drivers or wiring.

1. Driver Access: Drivers are accessible by separating column sections. Each driver is held by 4 screws.
2. Wiring Harness: Check for pinched or frayed wires along the column length.
3. Connector Cleaning: Clean column base pins and power stand socket with contact cleaner.
4. Telescoping Mechanism: Lubricate with dry silicone spray if movement is stiff. Do not use oil-based lubricants.
5. Grille Maintenance: Clean fabric grille with soft brush or low-suction vacuum.

Bass Module Service

B1 and B2 modules have similar service procedures.

1. Woofer Replacement: Remove grille, unscrew woofer, disconnect leads. Note polarity.
2. Port Tube: Ensure port tube is secure and not obstructed.
3. Terminal Cup: Check for loose solder joints on binding posts.
4. Enclosure Integrity: Inspect for cracks or air leaks. Re-seal with silicone if necessary.
5. Crossover (B2): Internal passive crossover network. Test inductors and capacitors for values.

Tip: When testing a bass module alone, use an external amplifier rated for 4-8 ohms.

Electrical Schematics

Refer to official Bose schematic diagrams (not included in public documentation). Key circuits:

Power Supply Section: SMPS topology with PFC. Includes bridge rectifier, switching transistors, control IC, and multiple output windings.

Amplifier Section: Class-D amplifier blocks for array (stereo) and bass module (mono). PWM controller and output MOSFETs.

Control & Protection: Microcontroller for system management, thermal protection, clip limiting, and fault detection.

Input Stage: Balanced microphone/line preamplifiers with gain control and phantom power supply.

Note: Schematics are proprietary to Bose. Service centers have access to full documentation.

Troubleshooting & Diagnostics

Factory Reset: Unplug unit. Hold down "Shape" button while plugging in. Release after 10 seconds (resets all settings).

Bose Service: For complex issues, contact Bose Professional Support or an authorized service center. Visit www.bose.com/prosupport.