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| Nokia 105 TA-1575 SS internal circuit, SC6531E CPU, charging IC, GSM section, display connection and board repair details. |
Nokia 105 TA-1575 SS Circuit Details and Board Overview.
The Nokia 105 TA-1575 SS is a compact 2G feature phone designed around a simple hardware architecture. For mobile technicians, the handset is more interesting from a board-repair perspective than from a specification perspective because the main processor, GSM section, charging circuit, display interface, keypad and audio functions are tightly integrated into a small PCB.
The official HMD documentation confirms that TA-1575 is one of the Nokia 105 models covered by the manufacturer’s user documentation, while HMD’s current specifications identify the Nokia 105 as a 1.8-inch feature phone with GSM connectivity and a 1000 mAh battery.
The board-level component markings mentioned in repair references, such as SC6531E, RTM7276F and NMPB 2012, are useful for technicians, but exact component identification can vary by PCB revision. Therefore, the physical board marking should always be checked before replacing an IC.
Nokia 105 TA-1575 SS Basic Hardware Specifications.
The following specifications combine the model information and the board-level details supplied for this circuit reference. Some internal component information is intended for repair identification rather than consumer specification purposes.
| Component | Details |
|---|---|
| Model Number | TA-1575 / TA-1575 SS |
| Model Name | Nokia 105 |
| Processor / Chipset | Spreadtrum SC6531E |
| Network | 2G GSM |
| GSM Bands | 900 / 1800 MHz |
| Crystal Reference | P26, 26 MHz |
| Network IC Reference | RTM7276F |
| Charging IC Reference | NMPB 2012 |
| Battery | 1000 mAh class for the official TA-1575 listing |
| SIM | Single SIM variant |
| Display | Approximately 1.8 inch |
| Display Resolution | 160 × 120 is reported in the supplied board reference; some retail listings report 160 × 128 for TA-1575 SS |
| Display Connector | 16-pin connection is reported in the supplied circuit reference |
| External Memory Slot | Not applicable in the supplied board reference |
| Main Board | Compact feature-phone PCB |
HMD’s official specification page lists the Nokia 105 display as 1.8 inches and the battery as 1000 mAh, while third-party retail listings for TA-1575 SS identify the SC6531E processor and 2G GSM operation.
Internal Circuit Architecture of the Nokia 105 TA-1575 SS.
The easiest way to understand the Nokia 105 circuit is to divide the motherboard into functional blocks rather than looking at individual components in isolation.
A simplified signal flow can be understood as:
Battery → Power Management → Main Processor → Display / Keypad / Audio
At the same time:
SIM → GSM Baseband → RF/Network Section → Antenna
And for charging:
Micro-USB Charger → Charging Circuit → Battery → System Power Rails
The crystal oscillator provides the reference clock required by the communication and processing section. Because this is a compact feature phone, several functions that would normally be distributed among multiple chips in a smartphone can be integrated into or controlled by a highly integrated feature-phone chipset.
Problem: Nokia 105 TA-1575 SS Power and Charging Section.
Charging faults are among the most common hardware issues encountered on older feature phones. A phone may show no charging indication, charge very slowly, restart during charging or remain completely dead because of a problem in the charging path.
Charging IC and Power Flow.
The supplied circuit reference identifies the charging controller as NMPB 2012 with an 8-pin package. The exact function of every pin should be confirmed from the particular PCB revision before performing board-level repair.
The basic charging path can be treated as:
USB Input → Protection / Input Path → Charging IC → Battery
The charging section controls the current supplied to the battery and works with the phone’s power-management circuitry to keep the system supplied during charging.
A technician should first inspect the charging connector, solder joints, input line, protection components and battery voltage before assuming that the charging IC itself is defective.
Solution: Basic Charging Fault Diagnosis.
When the Nokia 105 TA-1575 SS does not charge, a practical inspection sequence is more useful than immediately replacing an IC.
Check the charging connector for mechanical damage and loose solder joints. Then inspect the input path for broken tracks, damaged protection components or corrosion.
The battery itself should also be checked. A deeply discharged or damaged battery can create symptoms that look like a charging-IC fault.
If the charger input reaches the board but the battery does not receive the expected charging voltage or current, the charging circuit becomes a stronger suspect. At that stage, voltage measurements around the charging controller should be compared with a known-good board or a reliable schematic rather than relying on guessed pin values.
Problem: Nokia 105 TA-1575 SS CPU and Processing Section.
The supplied repair information identifies the main chipset as Spreadtrum SC6531E. This is a feature-phone chipset associated with low-end GSM handset designs.
SC6531E Processor Role.
The main chipset is responsible for the phone’s core processing functions and supports the communication and user-interface operations required by a basic feature phone.
Instead of using the type of multi-chip architecture commonly found in modern smartphones, feature-phone designs can integrate many essential functions around a highly integrated baseband platform. This keeps the PCB small and reduces power consumption.
The frequently repeated claim that this chipset has a 2 GHz primary clock should not be treated as an official TA-1575 specification. Retail listings currently identify the SC6531E in TA-1575 SS units but report a much lower clock figure, while HMD does not publish the chipset clock speed on its consumer specification page.
Solution: CPU-Related No-Power or Dead-Phone Diagnosis.
A completely dead Nokia 105 should not be diagnosed as a CPU fault simply because the display does not turn on.
First verify the battery, battery connector, main power rails, charging path and power-on key circuit. A broken supply line or shorted component can prevent the processor from starting even when the chipset itself is healthy.
If the required supply rails are present and the phone still shows no response, board-level inspection should continue around the processor and its clock source. Reflowing or replacing a chipset without confirming the fault can create additional PCB damage.
Problem: GSM Network and Crystal Section.
The Nokia 105 TA-1575 SS is a 2G GSM feature phone. HMD’s current Nokia 105 specification lists GSM operation at 900/1800 MHz for the model shown on its official India specification page.
26 MHz Crystal and Network Reference.
The supplied repair reference identifies the crystal as P26 with a 26 MHz frequency. A crystal oscillator provides a stable timing reference for communication and processing circuitry.
The network section is also identified with the RTM7276F marking in the supplied board information. However, the exact internal function and pin-level implementation of this IC should be verified against the actual PCB revision before publishing a repair voltage chart.
The important point for diagnosis is that the GSM section depends on stable power, clock reference, baseband processing and RF signal paths. A failure in any one of these areas can produce network-related symptoms.
Solution: No Network or SIM Detection Diagnosis.
For a Nokia 105 with no network, begin with the SIM connector and its contacts. Check for dirt, corrosion, broken solder joints and damaged tracks.
Next, inspect the antenna path and RF-related components. If the SIM is detected but the handset shows no network, the fault may be further into the GSM section rather than in the SIM interface.
The crystal circuit should also be considered when there are abnormal communication symptoms, but the crystal should not be replaced without confirming the clock-related fault.
Problem: Nokia 105 TA-1575 SS Display Not Working.
The supplied board reference identifies a small display with a 16-pin interface. HMD officially lists the Nokia 105 display size as 1.8 inches.
Display Circuit Explanation.
The display receives power and control/data signals from the main circuit. In a feature phone, the display interface is considerably simpler than the high-speed display interfaces found in smartphones.
The general path is:
CPU / Display Controller → Display Connector → LCD Module
The connector carries the required display power, control and data signals. Because the exact pin assignment depends on the display and PCB revision, a generic 16-pin diagram should not be treated as an exact TA-1575 pinout unless it has been verified against the board.
Solution: Blank Display and Display Connector Repair.
If the phone powers on but the screen remains blank, inspect the display connector first.
Look for bent contacts, damaged connector pins, cracked solder joints, oxidation and broken PCB traces. A damaged display flex or poor connector contact can produce the same symptom as a more serious motherboard fault.
If the backlight or display power section is separate from the data path on the particular board revision, those sections should be measured independently. The actual board layout should always be used for component identification.
Problem: Nokia 105 Keypad and User Input Fault.
The Nokia 105 uses a traditional physical keypad rather than a touch interface. Such keypads commonly use a matrix arrangement in which several keys share electrical lines.
Keypad Circuit Explanation.
The keypad works through rows and columns connected to the main processor. When a key is pressed, it connects a particular row and column combination, allowing the processor to determine which button was pressed.
This method reduces the number of individual I/O connections required for a complete keypad.
Solution: One or More Keys Not Working.
When a single key stops responding, inspect the keypad contact, rubber key membrane, PCB contact area and nearby tracks.
If several keys in the same row or column fail simultaneously, the fault is more likely to involve a common track, connector or processor-side keypad line than several separate key contacts failing at exactly the same time.
Problem: Nokia 105 Audio Section Not Working.
The audio system handles the earpiece or loudspeaker output, microphone input, ringtones and alert sounds.
Audio Circuit Explanation.
The supplied reference describes the audio function as integrated into the main processor rather than using a separate externally mounted audio IC.
This type of integration is normal for simple feature-phone hardware because it saves PCB space and reduces the number of external components.
The practical signal chain can be understood as:
Microphone → Main Audio/Baseband Section → Earpiece or Speaker
For outgoing audio faults, inspect the microphone and its PCB contacts. For incoming audio faults, inspect the earpiece or loudspeaker, contact springs and related traces.
Solution: No Sound or Low Audio.
Start with the physical audio component before suspecting the main processor. Dust, oxidation, damaged speaker contacts or a defective microphone can create a complete audio failure.
If the audio component tests correctly, continue toward the processor-side audio path and supply lines. Avoid applying unknown voltages directly to audio connectors because inappropriate external voltage can damage the phone. HMD’s own user guidance warns against connecting a voltage source to the audio connector.
Problem: Battery and Power Management Issues.
The official HMD listing for the TA-1575 model identifies a 1000 mAh battery.
Power Management Circuit.
A feature phone still requires several regulated supply rails even though its hardware is much simpler than a smartphone.
Power must be distributed to the processor, GSM section, display, audio circuitry and other peripheral components while keeping battery consumption under control.
The supplied script describes the power-management function as being integrated into the main processor. This is a board-level observation that should be verified against the individual PCB revision rather than treated as a universal specification for every TA-1575 board.
Solution: Fast Battery Drain or Random Shutdown.
Before replacing the processor or charging IC, check the battery condition and inspect the main supply line for abnormal current consumption.
A shorted capacitor or damaged peripheral component can pull down a power rail and cause boot loops, shutdowns or excessive battery drain.
A controlled current-consumption test with a suitable laboratory power supply can help a technician determine whether the phone is drawing normal startup current or entering a fault condition.
Internal Memory and Storage Information.
The supplied script describes the board as having extremely small ROM and RAM figures, such as 4000 KB ROM and 30 KB RAM. These figures should not be presented as the official consumer memory specification of the Nokia 105 TA-1575.
Current retail listings for TA-1575 SS units instead describe 32 MB RAM and 32 MB internal storage, although those retailer specifications are not equivalent to an official HMD chipset datasheet.
For repair work, the more important point is that this is a basic feature-phone platform with limited storage compared with smartphones. Its architecture is designed around calls, SMS, contacts and lightweight feature-phone software rather than modern Android applications.
Nokia 105 TA-1575 SS Circuit Repair Workflow.
A systematic repair process reduces the chance of replacing a good IC unnecessarily.
Step 1: Check the Battery and Connector.
Measure the battery condition and inspect the battery terminals. A weak battery or poor contact can imitate a motherboard problem.
Step 2: Inspect the Charging Path.
Check the USB connector, charging input path and charging-controller area. Look for broken tracks, corrosion and physically damaged components.
Step 3: Check Main Power Rails.
Confirm that the main power section is producing the expected supply rails before moving toward the processor or GSM section.
Step 4: Check the Clock Reference.
If the board has abnormal startup or communication behavior, inspect the 26 MHz crystal circuit identified in the supplied board reference.
Step 5: Check SIM and GSM Sections.
For network problems, inspect SIM contacts, antenna-related components and the RF/baseband path before concluding that the main chipset is defective.
Step 6: Check Display and Keypad.
For user-interface faults, inspect the display connector, keypad contacts and related PCB traces. These are common physical failure points and are easier to verify than a processor fault.
What a Nokia 105 TA-1575 SS Schematic Can Tell a Technician.
A proper schematic is valuable because it shows electrical relationships rather than only the physical positions of components.
A useful Nokia 105 circuit diagram should ideally identify the power rails, processor connections, charging path, crystal circuit, SIM interface, display connector, keypad matrix, audio section and GSM-related components.
A board photograph alone can help with component location, but it cannot reliably provide voltage values, exact signal direction or every internal connection. For this reason, a schematic PDF or verified boardview should be used whenever an exact pinout is required.
The 16-pin display connection, NMPB 2012 charging reference and RTM7276F network reference mentioned in repair material are useful starting points, but exact pin-to-pin measurements should be taken from the specific TA-1575 PCB revision.
Nokia TA-1575 SS Component Summary.
The most important board-level references can be summarised as follows:
SC6531E: Main feature-phone processor/baseband platform.
P26, 26 MHz: Crystal reference identified in the supplied circuit data.
RTM7276F: Network-section IC reference supplied for the board.
NMPB 2012: Charging-section IC reference supplied for the board.
1.8-inch display: Official HMD specification for the Nokia 105.
16-pin display interface: Pin count reported in the supplied repair reference; verify before using it as a universal pinout.
1000 mAh battery: Official HMD specification for the TA-1575 model listing.
Official Nokia 105 TA-1575 Information.
HMD’s official documentation identifies TA-1575 among the models covered by the Nokia 105 user guide. The official India specification page also identifies Model: TA-1575 and lists the 1.8-inch display, GSM connectivity and 1000 mAh battery.
Official HMD reference: Nokia 105 Official Specifications
Note: Internal IC markings, display pin counts and board-level values should be verified against the exact TA-1575 PCB revision before carrying out component-level repair.
Disclaimer: This article is intended for educational and technical reference purposes. Board-level repair should be performed by a qualified technician using proper measurement equipment and a verified schematic or boardview. Component markings and circuit layouts can differ between hardware revisions, so do not use unverified pinouts or voltage values as the sole basis for repair.
