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| T800/T900 Smart Watch motherboard circuit details with JQ7011 CPU, CSI8160 touch IC, charging IC, wireless charging, and repair reference. |
T800 and T900 Smart Watch Motherboard Circuit Details.
The T800 and T900 series smart watches use a compact motherboard that combines power management, charging, touch control, audio, vibration, display, wireless charging, and health-sensing functions into a very small circuit area. For technicians, understanding the board-level components is useful when troubleshooting charging problems, power failure, touch issues, display faults, vibration problems, or audio-related faults.
This guide is based on the LJ736-MB-V2.3 board and the component information supplied for the S2335017 unit. Component markings can vary between production batches, so the actual board should always be checked before replacing an IC or transistor.
Board Identification.
The motherboard information provided for this unit is:
Board Number: LJ736-MB-V2.3
Serial Number: S2335017
Power and CPU IC: JQ7011
Touchscreen Controller IC: CSI8160
Charging IC: 9212
Charging Protection IC: 61N UE
Switching IC: UC25H0 16
The motherboard contains five listed ICs and four listed transistors. Together, these components control the primary electrical and functional sections of the smartwatch.
Main Hardware Components.
The internal hardware includes the motherboard, magnetic wireless charging circuit, vibrator motor, microphone, mini speaker, display assembly, rechargeable battery, power switch, and health measurement sensor system.
The motherboard is the central electronic platform. It receives battery power, manages system functions, processes touch input, controls different output devices, and coordinates communication between several functional sections.
Motherboard.
The motherboard carries the main integrated circuits, transistor-based switching sections, connectors, power paths, and signal paths required for normal smartwatch operation.
Because the board is extremely compact, a single damaged component can affect several symptoms at the same time. For example, a power rail problem may appear as a dead watch, charging failure, display failure, or repeated restarts.
Wireless Magnetic Charging Module.
The wireless charging section transfers electrical energy from the external charging coil to the receiver coil inside the watch. The magnetic alignment system helps maintain a usable charging connection without requiring a conventional charging port.
Vibrator Motor.
The vibrator provides haptic feedback for calls, notifications, alarms, touch actions, and other system events. It is controlled electronically through the motherboard.
Microphone.
The microphone captures voice and other nearby audio for supported calling, recording, or voice-related functions. The specified microphone connection is a two-pin Mic +/− arrangement.
Mini Speaker.
The speaker produces notification sounds, alerts, voice output, and other audio generated by the smartwatch.
Display Assembly.
The display is connected to the motherboard through a flexible connection. The display assembly includes the screen, flex cable, and related electrical connections required for image output and touch functionality.
Battery.
The rechargeable battery supplies the main operating power to the smartwatch. Battery voltage, charging current, protection, and power distribution must remain within the limits of the actual battery and circuit design.
Power Switch.
The power switch provides the user input required to turn the watch on, wake it, or perform supported power-related actions. A transistor-controlled section is used to manage this function electronically.
Health Measurement Sensor System.
The watch may contain sensors designed to collect biometric or activity-related measurements. The exact sensor configuration can vary between T800 and T900 variants, so technicians should identify the actual sensor package present on the board rather than assuming every model uses the same hardware.
IC Identification and Functions.
The five listed ICs perform different jobs across the smartwatch circuit. Correct identification is especially important during motherboard repair because similar-looking SMD packages can have completely different functions.
JQ7011 Power and CPU IC.
IC Number: JQ7011
Other Marking: BP1N725
Pin Count: 40 Pins
The JQ7011 is identified in the supplied board information as the main power and processing IC. In the smartwatch, this section handles core system processing and coordinates multiple functions of the device.
Its 40-pin package provides connections for different power, control, and signal paths. It also communicates with supporting circuits such as the charging section and touchscreen controller.
For repair work, a completely dead watch, abnormal startup, unstable operation, or a missing power rail can point toward a problem in the main processing or power-management section. However, the JQ7011 should not be replaced simply because a watch does not turn on. Battery condition, charging protection, switch circuitry, and shorted power rails should be checked first.
CSI8160 Touchscreen Controller IC.
IC Number: CSI8160
Other Marking: 33X09
Pin Count: 20 Pins
The CSI8160 is identified as the touchscreen controller. Its job is to process electrical signals generated when the user touches the screen and convert those signals into information that the main system can interpret.
A faulty touchscreen controller or its surrounding circuit can cause symptoms such as no touch response, partial touch operation, ghost touches, or intermittent touch behaviour.
Before replacing the IC, the display flex connection, connector contacts, supply voltage, ground connection, and visible PCB damage should be inspected carefully.
61N UE Charging Protection IC.
IC Number: 61N UE
Other Marking: 61N UE
Pin Count: 4 Pins
The 61N UE device is listed as the charging protection section of the motherboard. Its purpose is related to protecting the charging path and battery circuit against abnormal electrical conditions.
Depending on the exact board implementation, protection circuitry can help isolate the battery or charging path during conditions such as overcurrent, short circuit, or abnormal voltage.
Because a small protection component can stop the charging path completely when damaged, technicians should test the charging input, protection path, and battery voltage before assuming the main charging IC is defective.
9212 Charging IC.
IC Number: 9212
Other Marking: N3X06
Pin Count: 8 Pins
The 9212 is identified as the smartwatch charging IC. It controls the charging path and manages the electrical conditions required to charge the internal rechargeable battery.
A problem in this section may produce symptoms such as no charging, very slow charging, repeated charging connection and disconnection, excessive charging temperature, or a charging indicator that appears but does not increase battery level.
When troubleshooting, the charging coil output, protection circuit, charging IC input, charging IC output, battery voltage, and ground connection should be checked in a logical sequence.
UC25H0 16 Switching IC.
IC Number: UC25H0 16
Other Marking: BP17170 / 2327
Pin Count: 8 Pins
The UC25H0 16 is identified as a switching IC used within the power-management and signal-control sections of the motherboard.
A switching device can be involved in regulating or routing electrical power between different circuit sections. Because the exact schematic is not available here, the precise function of every pin should be confirmed with board-level measurements before applying a replacement component.
Transistor Identification and Functions.
Four transistors are listed on the motherboard. These small three-pin components are used as electronic switches or control devices for specific loads and functions.
J3Y Power Switch Control Transistor.
Transistor Marking: J3Y
Pin Count: 3 Pins
The J3Y transistor is identified as the power switch control device. It helps control the electronic power-on or power-control path when the user operates the watch switch.
A damaged transistor in this area can result in a power button that appears to work mechanically but fails to activate the main circuit.
A2SHB Scrolling Control Transistor.
Transistor Marking: A2SHB
Pin Count: 3 Pins
The A2SHB transistor is identified as part of the scrolling control section. It assists the circuit responsible for navigation or scrolling-related control functions.
Since the same marking is also listed for the vibrator control transistor, board location and surrounding components are important when identifying the exact circuit function.
662K LED Control Transistor.
Transistor Marking: 662K
Pin Count: 3 Pins
The 662K transistor is used for LED control according to the supplied circuit information. It can control the switching of an LED-related load, helping the motherboard manage illumination according to the operating condition.
A2SHB Vibrator Control Transistor.
Transistor Marking: A2SHB
Pin Count: 3 Pins
Another A2SHB transistor is listed for vibrator control. This transistor works as an electronic switching element for the vibration motor.
If vibration has stopped working while the rest of the smartwatch operates normally, the motor, supply voltage, transistor, control signal, and PCB connections should be checked before replacing the transistor.
Speaker and Vibrator Specifications.
The audio and haptic components operate from dedicated electrical paths on the motherboard.
Smart Watch Speaker.
Rated Power: 0.60–0.90 W
Resistance: 15–30 Ohms
The mini speaker produces sound for calls, alerts, notifications, and other supported audio functions. Its resistance should be measured carefully before replacement because an incorrect speaker load can affect the audio circuit.
When a smartwatch has no sound, check the speaker coil, solder joints, connector or flex connection, amplifier path, and supply voltage before concluding that the motherboard IC has failed.
Vibrator Motor.
Operating Voltage: 2.8–3.7 V
The vibration motor provides physical feedback when receiving notifications, calls, alarms, or other haptic commands.
A useful repair sequence is to verify the motor itself first, then inspect the motor supply, transistor switching stage, control signal, and ground path.
Wireless Magnetic Charging Circuit.
The wireless charging system is one of the most important sections of the T800 and T900 motherboard because charging depends on correct alignment, coil transfer, protection, and battery management.
Magnetic Charging Input.
Specified Input Voltage: 5 V
Specified Input Current: 1.2–2 A
The external charging transmitter supplies power through magnetic coupling. The magnetic connection is designed to maintain a close electrical transfer path without using a traditional charging connector.
Receiver Coil.
Receiver Coil Size: 3 mm
Receiver Output Voltage: 5 V
Receiver Output Current: Up to 1 A
Normal Operating Distance: 2–10 mm
The receiver coil is located inside the smartwatch and captures the transferred magnetic energy. Its output feeds the charging circuit, where the incoming power is managed before reaching the battery.
The specified charging distance is important because excessive separation or poor alignment can reduce the available transferred power. A weak magnetic connection can therefore look like a charging IC fault even when the motherboard is healthy.
Problem and Solution Guide.
Board-level smartwatch repair should begin with basic electrical checks rather than immediate IC replacement. The objective is to identify the fault section first and then test the relevant component.
Problem: Smart Watch Does Not Power On.
Start by checking the battery voltage. A deeply discharged, damaged, or disconnected battery can make a healthy motherboard appear completely dead.
Next, inspect the power switch, J3Y transistor, battery connection, ground path, and major power rails.
If the battery voltage is normal but the main power rail is missing, trace the circuit from the battery and power-control section toward the main JQ7011 area.
A short circuit on a power rail should be identified before replacing any major IC.
Problem: Smart Watch Is Not Charging.
Check the magnetic charger and make sure the charging coil is correctly aligned with the receiver coil.
Then inspect the receiver coil, coil solder connections, charging input path, 61N UE protection section, and 9212 charging IC.
If the charger provides the expected input but the battery does not receive charging current, measure the circuit section by section instead of replacing the charging IC immediately.
Problem: Charging Starts but Battery Percentage Does Not Increase.
This symptom can be caused by a weak charging path, defective battery, high-resistance connection, protection circuit issue, or charging management fault.
Check battery voltage before and during charging. Also inspect for damaged coil connections, abnormal heating, or unstable charging voltage.
A battery that has degraded internally may accept little or no useful charge even when the charging IC is functioning normally.
Problem: Touchscreen Is Not Working.
Inspect the display flex cable and connector first. A loose, cracked, contaminated, or damaged connection can produce complete or partial touch failure.
After confirming the mechanical connection, check the touchscreen controller supply and surrounding circuit.
The CSI8160 should only be considered a replacement candidate after the power and signal conditions around the controller have been verified.
Problem: Vibration Is Not Working.
Test the vibrator motor independently when appropriate and safe to do so.
Then check its supply voltage, transistor switching path, solder joints, and motherboard control signal.
Because the vibrator is a load driven through a transistor stage, a failed motor and a failed control transistor can produce similar symptoms.
Problem: Speaker Has No Sound.
Inspect the speaker resistance first. An open speaker coil or damaged speaker connection can completely remove audio output.
Next, check the speaker solder points, flex or wiring, supply path, and audio output section.
Do not assume that the main CPU or motherboard is faulty simply because the speaker is silent.
Problem: Smart Watch Restarts Repeatedly.
Repeated restarting can be caused by unstable battery voltage, poor battery contact, a power-management problem, or a short or overload on one of the power rails.
Measure the battery and main supply during startup. If the voltage drops sharply when the watch attempts to boot, the battery or power path deserves attention before the CPU section is blamed.
Problem: Wireless Charging Works Only at Certain Positions.
Check the receiver coil alignment, magnet position, coil connection, and charging input stability.
Because wireless charging depends on magnetic coupling, even a small change in coil position or physical distance can significantly affect power transfer.
A damaged or shifted receiver coil can therefore create an intermittent charging problem.
Step-by-Step Circuit Repair Method.
Step 1: Identify the Board.
Confirm that the motherboard is the LJ736-MB-V2.3 version or another compatible board version. Record the board marking before ordering replacement components.
Step 2: Perform a Visual Inspection.
Look for burned components, cracked SMD parts, corrosion, broken solder joints, damaged flex cables, lifted pads, and signs of liquid exposure.
A microscope is highly useful for this type of compact PCB inspection.
Step 3: Check Battery Voltage.
Measure the battery directly with a suitable multimeter. Do not rely only on the display's battery percentage.
A battery reading outside the expected range of the specific battery pack requires careful investigation before further circuit testing.
Step 4: Check the Charging Path.
Follow the path from the magnetic receiver coil toward the protection section and 9212 charging IC.
Compare measured voltages against the expected circuit behavior rather than relying on a single voltage reading.
Step 5: Check Power Management.
Verify the power switch path and J3Y transistor. Then inspect the relevant rails associated with the JQ7011 power and processing section.
Step 6: Test the Functional Sections.
After the main power system is confirmed, test touch, display, speaker, microphone, vibrator, and other peripherals separately.
This approach prevents unnecessary replacement of expensive or difficult-to-rework components.
Step 7: Confirm the Repair.
After replacing a faulty component, test charging, startup, display, touch response, audio, vibration, wireless charging, and battery behaviour.
A repair should be considered complete only after the affected function remains stable during repeated testing.
Practical Board Repair Tips.
Because the T800 and T900 motherboard is densely populated, excessive heat can damage nearby components, flexible cables, pads, or the PCB itself.
Use proper ESD protection when handling the board. Avoid applying direct heat to the battery, especially during disassembly or soldering work.
When replacing an IC or transistor, first confirm the package marking, pin configuration, board orientation, and surrounding circuit. A visually similar SMD component is not automatically a valid replacement.
For diagnosis, a digital multimeter is essential. A bench power supply, microscope, hot-air rework station, soldering iron, flux, and suitable test probes can make board-level troubleshooting significantly easier.
Supported Smart Watch Models.
The supplied information lists the following compatible or related models:
T900
S-T800
T900 Ultra
8 Series
Compatibility can vary between revisions, manufacturers, and board versions. Always compare the actual motherboard number and component layout before using this information for a replacement board or component.
T800 and T900 Motherboard Reference Summary.
| Section | Component | Marking | Pin Count / Rating |
|---|---|---|---|
| Main Power and CPU | Power/CPU IC | JQ7011 | 40 Pins |
| Touch Control | Touch IC | CSI8160 | 20 Pins |
| Charging Protection | Protection IC | 61N UE | 4 Pins |
| Charging Management | Charging IC | 9212 | 8 Pins |
| Switching | Switching IC | UC25H0 16 | 8 Pins |
| Power Switch | Transistor | J3Y | 3 Pins |
| Scrolling Control | Transistor | A2SHB | 3 Pins |
| LED Control | Transistor | 662K | 3 Pins |
| Vibrator Control | Transistor | A2SHB | 3 Pins |
| Speaker | Mini Speaker | — | 0.60–0.90 W, 15–30 Ohms |
| Vibrator | Vibration Motor | — | 2.8–3.7 V |
| Wireless Receiver | Charging Coil | — | 5 V, up to 1 A |
Note: The component markings and electrical values above are board-reference information for the specified T800/T900 hardware. Always verify the exact revision, pinout, and voltage at board level before attempting a repair or component replacement.
Disclaimer: This article is provided for technical reference and educational purposes. Smartwatch circuit designs can vary by manufacturer, board revision, and production batch. Incorrect voltage application, soldering, battery handling, or IC replacement can permanently damage the motherboard or create a safety hazard. Where no manufacturer schematic or official service manual is available, the listed component functions should be treated as board-specific reference information and confirmed by measurement before repair.
