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| Detailed BoAt Rockerz 255 Pro Plus AB1561M circuit overview, including the charging IC, battery, microphone, crystal oscillator, USB Type-C port, LEDs, and repair points. |
BoAt Rockerz 255 Pro Plus AB1561M Circuit Repair Guide: Components, Testing and Troubleshooting
The BoAt Rockerz 255 Pro Plus is a compact Bluetooth neckband built around a small number of important electronic circuits. Although the PCB looks simple from the outside, the Power/Bluetooth SoC, charging section, microphone, crystal oscillator, switches, LEDs, USB Type-C connector, and Li-Polymer battery all have to work together correctly.
This guide explains the reported internal circuit configuration of the BoAt Rockerz 255 Pro Plus, motherboard number 255PRO_PLUS_AB1561M, Version 4, and the major components found on the board. It also focuses on practical circuit troubleshooting and repair methods so that a technician can understand where to start when the neckband does not power on, does not charge, has Bluetooth problems, or shows abnormal battery behaviour.
The component markings and electrical details below are based on the supplied board information. Exact pad functions should always be confirmed from the PCB itself before applying voltage, replacing an IC, or making a jumper connection.
BoAt Rockerz 255 Pro Plus Motherboard and Internal Components
The reported motherboard number is 255PRO_PLUS_AB1561M, with PCB version 4. The board contains two primary ICs and several supporting components responsible for power management, Bluetooth communication, charging, audio input, timing, user controls, and status indication.
| Component | Reported Specification |
|---|---|
| Motherboard | 255PRO_PLUS_AB1561M, Version 4 |
| Main IC | AIROHA AB1561M, 40-pin reported connection |
| Charging IC | Universal 3105, 8-pin |
| Microphone | SH 027 Digital SMD Microphone, 4-pin |
| Crystal Oscillator | 26.00 MHz, 4-pin |
| USB Connector | USB Type-C, 16-pin reported connector |
| Push Switch | SMD Mini Push Switch, 2×3×0.6 mm |
| Indicator LEDs | Red and Blue SMD LEDs |
| Battery | XD 481036 Li-Polymer, about 3.7V nominal, 4.4V maximum charge |
Understanding the role of every section is useful because a single damaged component can create symptoms that appear to be caused by another circuit.
Problem: BoAt Rockerz 255 Pro Plus Does Not Power On
Check the Battery Voltage First
A no-power complaint should normally begin with the battery rather than the main IC. Measure the battery voltage directly across the positive and negative terminals using a reliable digital multimeter.
The supplied battery information identifies the XD 481036 as a rechargeable Li-Polymer battery with a nominal voltage around 3.7V and a maximum charging voltage of 4.4V.
A very low battery voltage can prevent the main circuit from starting. However, a low reading should not automatically be interpreted as a charging-IC failure. The battery, protection path, charging circuit, connector, and PCB traces should all be considered.
Inspect the Power Path Around the AB1561M
The AIROHA AB1561M is the central system IC in this board. It is responsible for Bluetooth functionality, audio processing, control signals, and several power-related operations.
According to the supplied identification:
IC: AIROHA AB1561M
Serial marking: ETTHGU81
Manufacturer code: 2309TDDAG
Reported package connection: 40 pins
Because the AB1561M is a high-density SoC, a technician should avoid randomly injecting voltage into individual pins. First confirm the battery rail, ground, charging path, and visible PCB damage.
Check the Power Button Circuit
The mini push switches are connected to the control section of the AB1561M. A faulty switch, cracked solder joint, or broken PCB trace can make a healthy neckband appear completely dead.
Check the switch electrically with continuity mode. When the button is pressed, the expected switching action should be present according to the actual PCB connection.
If the switch itself works but the signal does not reach the control IC, inspect the copper trace, solder pads, and nearby passive components.
Problem: BoAt Rockerz 255 Pro Plus Is Not Charging
Inspect the USB Type-C Connector
The USB Type-C connector is the first physical point to check when charging fails. The supplied board information describes a 16-pin Type-C connector used as the charging interface.
The important charging path is generally associated with:
VBUS input from the charger
Ground return
CC-related USB-C detection circuitry where implemented
Charging-IC input path
Battery charging output
Do not assume that every visible Type-C pin is used for charging in exactly the same way. Compact consumer devices often use only a subset of connector contacts for their actual function.
Check for 5V at the Charging Input
With a suitable charger connected, verify whether approximately 5V reaches the charging input path.
If 5V is present at the connector but missing at the charging IC, inspect:
Broken Type-C solder joints
Damaged PCB tracks
Protection components
Open resistors or fuses, if fitted
Corrosion around the connector
A loose USB-C connector can create intermittent charging problems that look like an IC fault.
Charging IC: Universal 3105
The supplied information identifies the charging controller as Universal 3105, with an 8-pin connection.
Its main job is to manage charging of the Li-Polymer battery and regulate the charging process rather than allowing the battery to receive an uncontrolled supply.
The reported charging path includes a 5V input from the Type-C connector and a controlled connection toward the battery. The charging controller also interacts with the rest of the system so the device can determine charging status.
The script refers to this section as both 3105 and 3108 in different places. For repair purposes, the actual marking printed on the installed IC and the PCB trace configuration should be treated as the authoritative identification.
Charging Current Should Not Be Judged by a Single Number
The supplied measurements mention approximately 0.05A to 0.60A during charging under different conditions and also mention a 2A charger input.
These values should not be confused with the actual battery charging current. A charger rated for 2A does not mean the neckband battery itself is charged at 2A. The charging IC determines how much current the battery receives according to the circuit design and operating condition.
This distinction is important during repair because connecting a high-current adapter does not force the battery to accept the adapter's maximum current.
Problem: Battery Charges Slowly or Stops Before Full Charge
Verify the Battery and Charging Voltage
The reported battery charging specification is approximately:
Nominal battery voltage: 3.7V
Maximum charging voltage: 4.4V
Battery model: XD 481036
Battery code: 1/CP5/11/38
A Li-Polymer cell intended for a 4.4V charging limit should not be treated like an ordinary 4.2V cell. The actual battery chemistry and charging specification must be confirmed before substituting another battery.
Never increase the charging voltage simply to make a battery charge faster.
Check Battery Internal Condition
A battery can show a reasonable voltage with no load and still collapse when the neckband attempts to start or transmit Bluetooth audio.
If the voltage drops sharply when the device powers on, the battery may have high internal resistance or may be reaching the end of its service life.
Swelling, physical damage, unusual heating, leakage, or a damaged pouch cell should be treated as a battery safety issue rather than a normal PCB repair.
AB1561M Power and Bluetooth SoC: Circuit Role
What the AB1561M Does
The AIROHA AB1561M is the core processing device described in the supplied board information. It handles the main digital functions required by the neckband, including Bluetooth communication, audio processing, control-button inputs, microphone processing, and interaction with status indicators.
A simplified functional flow can be understood as:
Battery → Power Management → AB1561M → Bluetooth / Audio / Control
The exact internal architecture is more complex than this simplified representation, but this model is useful for troubleshooting.
AB1561M Pin Functions
The supplied information groups the connections into power, Bluetooth, audio, control, and related functions.
Power-related connections provide operating voltage to the IC. Bluetooth-related connections handle wireless communication. Audio paths process signals associated with the microphone and speaker system, while control lines allow switches and LEDs to communicate with the main IC.
Because the AB1561M is a multifunction SoC, a failure inside the IC can produce several symptoms at the same time.
For example, a completely dead device may involve the power section, while a device that powers on but cannot pair may indicate a Bluetooth-related fault, crystal problem, software issue, or damage to the SoC.
26.00 MHz Crystal Oscillator and Clock Circuit
Why the Crystal Matters
The supplied board information identifies a 26.00 MHz crystal oscillator connected to the main IC.
A crystal does not function like a normal power component. It provides a stable frequency reference required by the digital electronics for timing and synchronisation.
The simplified relationship is:
Crystal Oscillator → Clock Reference → AB1561M System Timing
If the clock reference is missing or abnormal, the main IC may fail to initialise properly.
Crystal Troubleshooting
Crystal faults can be difficult to diagnose using only a standard multimeter because the oscillator operates at a high frequency.
A technician should first inspect for:
Cracked crystal body
Damaged solder joints
Corrosion around the crystal
Broken PCB traces
Missing or damaged nearby capacitive components
Where appropriate test equipment is available, an oscilloscope can provide more useful information than a continuity test.
Do not short the crystal pins or apply external voltage directly to them.
SH 027 Digital Microphone Circuit
Microphone Identification
The supplied information identifies the microphone as:
Part marking: SH 027
Type: Digital SMD microphone
Total pins: 4
Reported arrangement: two signal-related connections and two ground connections
A digital MEMS/SMD microphone requires the correct power and signal environment. It should not be tested like a simple two-wire electret microphone.
How the Microphone Works
The microphone captures sound and provides an electrical representation of the audio to the main processing circuit.
During a Bluetooth call, the microphone path can be represented conceptually as:
Voice → Microphone → AB1561M Processing → Bluetooth Transmission
A failure in the microphone, its supply, signal path, or the main IC can result in no microphone audio or distorted voice during calls.
Microphone Repair Tip
If the neckband speaker works normally but the other person cannot hear the user clearly, do not immediately replace the AB1561M.
First inspect the microphone opening, microphone solder joints, nearby contamination, and PCB tracks. Dust or adhesive covering the microphone acoustic opening can also reduce voice quality without any electronic component being defective.
USB Type-C Charging Connector Circuit
Type-C Connector Function
The USB Type-C connector provides the external charging interface. In the supplied information, the connector is identified as a 16-pin Type-C socket.
The most important electrical groups for a charging-only application are the power input and ground connections. Additional Type-C contacts may support identification, orientation, or other device-specific functions.
Type-C Repair Procedure
When the charging port is physically damaged, inspect the connector under magnification before attempting replacement.
Look for:
Lifted connector pads
Broken anchor joints
Bent internal contacts
Burn marks
Corrosion
Cracked PCB copper
Foreign material inside the connector
A replacement connector must match the PCB footprint. Two visually similar Type-C connectors can have different mechanical dimensions and pin arrangements.
Mini Push Switch Circuit
Switch Identification
The board uses mini SMD push switches, reported as approximately 2 × 3 × 0.6 mm.
These switches provide user input for functions such as power control, playback, or other commands assigned by the firmware.
How the Switch Signal Works
When a button is pressed, the electrical state of the switch changes. The AB1561M detects that change and interprets it according to its programmed function.
A simplified flow is:
Button Press → Control Signal → AB1561M → Device Action
The exact voltage level depends on the PCB design and internal pull-up or pull-down arrangement.
Switch Repair Tip
Before replacing a switch, check whether the switch pads themselves are intact. A missing pad or broken trace can make a new replacement switch appear faulty.
Red and Blue Indicator LED Circuit
LED Identification
The reported board configuration includes two SMD indicator LEDs:
Red LED
Blue LED
The supplied information identifies them as SMD indicators with an 0805-style marking/size reference. The actual component dimensions should be checked against the PCB before replacement because package markings can be interpreted differently across component suppliers.
LED Working Function
The LEDs provide visual feedback for different operating conditions.
The supplied behaviour describes the red indicator as being associated with charging, while blue illumination or blue/red blinking can indicate power, Bluetooth, or connection status.
The AB1561M controls these LED signals according to the firmware and device state.
LED Fault Diagnosis
If the neckband functions normally but an indicator does not illuminate, the problem may be limited to the LED branch.
Check the LED orientation, resistor path where present, solder joints, and PCB trace before assuming a processor failure.
A faulty LED is normally a much simpler repair than a damaged system IC.
XD 481036 Li-Polymer Battery Circuit
Battery Specification
The supplied battery information identifies:
Battery model: XD 481036
Battery type: Rechargeable Li-Polymer
Battery code: 1/CP5/11/38
Nominal voltage: approximately 3.7V
Maximum charging voltage: approximately 4.4V
The script includes two different values, 150mAh and 200mAh, for battery capacity. Because these values conflict, the exact capacity should be confirmed from the physical battery label rather than assuming either value is correct.
Battery Pin Connection
The positive terminal supplies the electronics through the charging and power-management path, while the negative terminal provides the ground return.
Before replacing the battery, verify:
Voltage rating
Maximum charging voltage
Physical dimensions
Connector or solder arrangement
Polarity
Required protection arrangement
Actual capacity
Using an incompatible Li-Polymer cell can create a serious charging and safety problem.
Problem: Bluetooth Is Not Working
Check the Power and Clock Sections
Bluetooth problems do not always mean that the antenna or main IC is defective.
A stable power supply and clock reference are essential for the AB1561M to initialize correctly.
Begin by checking whether the neckband powers on normally, whether the indicator behavior is normal, and whether the device responds to the control buttons.
If the device repeatedly restarts or behaves unpredictably, inspect the battery and power section before focusing on Bluetooth.
Inspect the Main SoC Area
The AB1561M contains a large portion of the Bluetooth system functionality. If the board has suffered liquid damage, overheating, physical bending, or an accidental short circuit, the SoC area should be inspected carefully.
Do not attempt unnecessary reflow or heating of the AB1561M simply because Bluetooth pairing fails. BGA and fine-pitch SoC repair requires proper equipment and a verified diagnosis.
Problem: Neckband Turns On but There Is No Audio
Check the Audio Path
When Bluetooth pairing works but sound is missing, separate the problem into three areas:
Bluetooth data reception → AB1561M audio processing → Speaker output
The microphone circuit is mainly associated with audio input during calls, whereas the speaker path handles audio output.
A technician should therefore determine whether the problem affects:
Music playback
Voice calls
Both channels
One side only
Audio at all volume levels
This symptom-based approach avoids replacing unrelated components.
Problem: Microphone Works Poorly During Calls
Check the SH 027 Microphone
Start with the physical microphone opening and solder area.
If the microphone has been exposed to sweat, dust, or moisture, contamination can reduce the acoustic response. A damaged microphone can also cause very low voice volume or a noisy call.
Where the microphone circuit uses digital signalling, ordinary analogue microphone substitution may not work correctly.
Practical BoAt Rockerz 255 Pro Plus Circuit Repair Workflow
Step 1: Perform a Visual Inspection
Before applying power, inspect the entire PCB under magnification.
Look for burnt components, cracked solder joints, corrosion, liquid residue, damaged connector pads, broken traces, and signs of previous repair work.
Step 2: Check Battery Voltage
Measure the battery directly at its terminals and confirm the reading is reasonable for the battery state.
Do not continue forcing a deeply discharged or physically damaged Li-Polymer cell.
Step 3: Check USB-C Input
Connect a known-good charger and verify whether the charging input reaches the charging section.
If 5V is present at the connector but not at the charging circuit, follow the PCB trace between those points.
Step 4: Inspect the Charging IC
Examine the Universal 3105 area for shorts, heat damage, corrosion, or abnormal resistance on the power rails.
A suspected short should be investigated before applying more power.
Step 5: Check Switch Operation
Test the mini push switches and verify that pressing them produces the expected electrical change.
A broken switch line can imitate a dead motherboard.
Step 6: Check Crystal and Main IC Support Components
If power is present but the system does not initialise, inspect the 26.00 MHz crystal and its surrounding components.
The crystal should not be replaced blindly; first inspect the associated PCB area and compare with a known-good board where possible.
Step 7: Check LEDs and Functional Feedback
Observe the red and blue indicators during charging, power-on, pairing, and button operation.
LED behaviour can provide useful diagnostic information because it tells the technician whether the firmware-controlled system is reaching particular operating states.
Important Repair Tips for This Neckband PCB
Note: Always confirm the actual PCB trace, component marking, polarity, and measured voltage before replacing or jumpering any circuit component.
A compact Bluetooth neckband should be repaired using a low-risk diagnostic sequence rather than random component replacement.
Use a current-limited bench supply when appropriate, especially when investigating suspected shorts. Current limiting can prevent additional damage while allowing the technician to observe how the board responds.
Avoid directly probing fine-pitch AB1561M pins with large metal tips. A slip can short adjacent pins and create a second fault.
When replacing the charging connector, inspect the PCB anchor points carefully. Mechanical damage around a Type-C socket is often more extensive than it appears from the outside.
When replacing the battery, verify polarity before connection. Reverse polarity can damage the power-management section and the main SoC.
Do not exceed the specified charging voltage of the battery. The reported XD 481036 battery is associated with a maximum charging voltage of approximately 4.4V, but the physical battery label should be treated as the final reference for replacement.
How the Complete Circuit Works Together
The complete operating process can be understood as a chain of interconnected sections.
When the neckband receives power from its battery, the power-management section supplies the required operating rails to the main electronics.
The AB1561M then handles system control, Bluetooth communication, audio processing, switch input, and indicator control.
When a USB Type-C charger is connected, the charging circuit receives external power and manages the charging process for the Li-Polymer battery.
The 26.00 MHz crystal provides the timing reference required by the main digital system.
The SH 027 microphone captures voice input for Bluetooth calls, while the push switches provide user commands.
Finally, the red and blue LEDs communicate operating status to the user without requiring a display.
This interaction is what makes the small PCB function as a complete Bluetooth audio system rather than a collection of independent components.
Final Repair Reference for BoAt Rockerz 255 Pro Plus
The most important reported board identifiers are 255PRO_PLUS_AB1561M, Version 4, AIROHA AB1561M, Universal 3105 charging IC, SH 027 digital microphone, 26.00 MHz crystal, USB Type-C connector, and XD 481036 Li-Polymer battery.
For practical troubleshooting, the best approach is to move from the simplest and safest checks toward the more difficult ones: physical inspection, battery measurement, Type-C input verification, charging-path testing, switch testing, crystal inspection, and finally detailed diagnosis of the AB1561M and other fine-pitch circuitry.
The supplied information should be used as a repair reference rather than as a guaranteed factory schematic. Exact pin functions, component values, and PCB routing should be confirmed from the actual board under repair before performing component-level work.
Disclaimer: This article is an educational repair reference; component markings and electrical specifications should be verified on the actual PCB and battery before any repair or replacement work.
