Bose QC3 Service Manual

The Bose QuietComfort 3 (QC3) Acoustic Noise Cancelling headphones are designed for superior noise reduction and audio performance. This service manual provides detailed information for authorized service personnel, covering safety procedures, disassembly/assembly, component identification, testing, troubleshooting, and replacement parts. Below are key sections for technical specifications, service procedures, and maintenance guidelines.

Features and Specifications

Key components: Acoustic Noise Cancelling circuitry, TriPort acoustic headphone structure, rechargeable battery, audio input cable, carrying case.

Feature	Description
Noise Cancellation	Active electronic noise cancellation with external microphone monitoring
Driver Type	Proprietary TriPort acoustic design
Frequency Response	Not specified publicly (proprietary)
Battery	Rechargeable lithium-ion (integrated)
Battery Life	Up to 20 hours (noise cancellation on)
Charging Time	Approximately 2 hours for full charge
Audio Input	Detachable audio cable with 2.5mm and 3.5mm connectors
Controls	Power/Noise Cancellation switch, battery status indicator
Weight	Approximately 5.5 ounces (156 grams)
Carrying Case	Included protective case

Safety Precautions

Before servicing, review all safety warnings and electrostatic discharge (ESD) procedures.

1. Power Off: Ensure the headphone is powered off and disconnected from any audio source.
2. Battery Safety: Disconnect battery before servicing internal components. Lithium-ion batteries can be hazardous if damaged.
3. ESD Protection: Use grounded wrist strap and anti-static mat when handling circuit boards.
4. Component Handling: Use appropriate tools to avoid damage to plastic clips and connectors.

WARNING! Only authorized service personnel should perform repairs described in this manual. Incorrect repair can cause injury or damage.

Tools and Equipment

Required tools for service procedures.

1. Torx T6 screwdriver
2. Plastic spudger or opening tool
3. Anti-static wrist strap
4. Multimeter
5. Soldering iron (fine tip)
6. ESD-safe work surface
7. Battery charger (Bose approved)

CAUTION! Use only specified tools to prevent damage to housing and components.

Disassembly Procedure

• Step 1 - Ear Cushion Removal: Gently pull ear cushion away from ear cup starting at the bottom edge.
• Step 2 - Outer Cover Removal: Remove four T6 Torx screws securing the outer cover to the housing.
• Step 3 - Driver Access: Carefully lift the outer cover to access the driver assembly and noise cancellation microphone.
• Step 4 - Battery Disconnection: Disconnect the battery connector from the main circuit board.
• Step 5 - Circuit Board Removal: Remove screws securing the circuit board and gently lift it from the housing.
• Step 6 - Driver Removal: Unclip the driver assembly from its housing for replacement.

Assembly Procedure

Reverse the disassembly steps, ensuring all components are properly seated.

1. Install driver assembly into housing, ensuring proper orientation.
2. Reinstall circuit board and secure with screws.
3. Reconnect battery connector to main circuit board.
4. Place outer cover and secure with four T6 Torx screws.
5. Reattach ear cushion by aligning and pressing evenly around the ear cup.
6. Perform functional test before returning to customer.

Tip: Ensure all cable routing is clear and no wires are pinched during assembly.

Component Identification

Main components and their locations.

Left Ear Cup: Primary circuit board, battery, power/NC switch, charge port.

Right Ear Cup: Driver assembly, external noise cancellation microphone.

Cable Assembly: Detachable audio cable with inline remote (if equipped).

Circuit Board: Main processor, noise cancellation circuitry, audio amplifier, battery management IC.

Circuit Diagrams

Reference diagrams for main board (available in full PDF version).

1. Power supply and battery charging circuit.
2. Noise cancellation microphone input and processing.
3. Audio amplifier and driver output stage.
4. Switch and indicator LED circuit.

Note: Complete schematics are proprietary and available only to authorized service centers.

Testing and Calibration

Post-repair verification procedures.

1. Battery Test: Charge fully and verify 20+ hour operation with noise cancellation on.
2. Noise Cancellation Test: Activate NC in quiet environment; should produce noticeable noise reduction.
3. Audio Test: Play test tones through all frequencies; check for distortion or imbalance.
4. Microphone Test: Verify external microphone is picking up ambient noise for cancellation.
5. Switch Test: Cycle power/NC switch multiple times to ensure reliable operation.

WARNING! Use Bose-approved test equipment and procedures for accurate calibration.

Troubleshooting Guide

Symptom	Possible Cause	Corrective Action
No power	Battery depleted/faulty	Charge for 2 hours; if no LED, replace battery.
Noise cancellation not working	Microphone failure/switch issue	Test external microphone; replace if faulty.
Audio in one ear only	Cable/driver issue	Test with known good cable; replace faulty driver.
Distorted audio	Driver damage	Replace driver assembly.
Battery not charging	Charging circuit/port issue	Check charge port for damage; replace main board if needed.

Reset: No user-resettable function. For persistent issues, replace main circuit board.

Replacement Parts List

Genuine Bose replacement parts (example part numbers).

• Battery Assembly: Part # 123456
• Driver (Left/Right): Part # 123457
• Ear Cushion Set: Part # 123458
• Audio Cable: Part # 123459
• Outer Cover Assembly: Part # 123460
• Main Circuit Board: Part # 123461
• Noise Cancellation Microphone: Part # 123462

CAUTION! Use only genuine Bose parts to maintain performance and safety.

Regulatory and Compliance

FCC Part 15: Class B digital device compliance. Contains lithium-ion battery; follow local disposal regulations. Copyright © Bose Corporation. All trademarks are property of Bose Corporation. For service support, contact authorized Bose service centers only.