By methodical tracing with a multimeter and carefully applying jumper paths, you can reliably bypass internal board fractures and restore the Nokia 105 RM-908 keypad back to fully operational status. To help tailor this guide further, let me know: Which are currently failing on your device? Do you have access to a multimeter and a soldering iron ?
When a track is broken ( OL ), you must run a micro-jumper wire from a functioning button or component along the same trace line to the broken button. Use the mapping below to find corresponding pins. The Horizontal Core Tracks (Inner Circles) Call Key ↔left-right arrow 1 ↔left-right arrow 2 ↔left-right arrow 3 Line 2: Left Selection ↔left-right arrow 4 ↔left-right arrow 5 ↔left-right arrow 6 Line 3: Right Selection ↔left-right arrow 7 ↔left-right arrow 8 ↔left-right arrow 9 Line 4: End/Power Key ↔left-right arrow * ↔left-right arrow 0 ↔left-right arrow #
: To restore settings without losing personal data, use *#7780# . General Keypad Usage For standard operation of the RM-908 keypad: Nokia 105 user guide: Keys and parts - HMD
If specific keys are not working, it is usually due to a break in the circuit tracks. Technicians use the following methods to troubleshoot: nokia 105 rm 908 keypad ways
Used to test continuity, trace tracks, and measure Diode Value / Ground Resistance (GR). For smooth solder joints and proper heat conduction. Isopropyl Alcohol (IPA)
The Nokia 105 RM‑908 uses a architecture to minimize the number of input/output (I/O) pins required on the main processor. Each key serves as a switch that connects a row line to a column line. When a key is pressed, the CPU detects the short circuit between a specific row and column and translates it into a character or command.
Like most feature phones, the Nokia 105 (2013) keypad functions using a simple cross-point matrix system. Each button consists of two separate electrical points: By methodical tracing with a multimeter and carefully
Before jumping wires, dismantle the phone:
| Row | Function | Test Point Example | |-----|----------|--------------------| | ROW0 | 1, 2, 3, Call | TP-205 | | ROW1 | 4, 5, 6, Left Soft | TP-206 | | ROW2 | 7, 8, 9, Right Soft | TP-207 | | ROW3 | *, 0, #, End/Power | TP-208 |
If the path is entirely lost inside the board, the final solution is to "re-ball" or revolve the IC , though a jumper is the preferred "quick way" for most technicians. 4. The Final Awakening When a track is broken ( OL ),
| Test Point Label | Signal | Location on PCB | |----------------|--------|------------------| | TP201 | COL0 | Near SIM holder | | TP202 | COL1 | Under keypad shield edge | | TP203 | COL2 | Adjacent to vibrator | | TP204 | COL3 | Near CPU pin 48 | | TP205 | ROW0 | Close to battery connector (-) | | TP206 | ROW1 | Below LCD connector | | TP207 | ROW2 | By microphone pads | | TP208 | ROW3 | Next to charging IC |
When prompted for the default Nokia security code, enter . Select Continue to erase and restore factory defaults.