Nokia 105 Rm 908 Keypad Ways File
In mobile phone hardware terminology, "ways" refer to the conductive paths (traces) on the Printed Circuit Board (PCB) that carry electrical signals from the keypad buttons to the Baseband Processor (CPU) or Keyboard Controller.
For the Nokia 105 RM-908, the keypad is arranged in a matrix grid (Rows and Columns). Each button acts as a switch that connects a specific Row line to a specific Column line.
When a "way" is broken (due to a cracked PCB, corroded via, or lifted pad near the connector), the processor never receives the signal for that specific row or column, causing an entire line of buttons to fail.
The keypad works on a Matrix system (Rows and Columns). nokia 105 rm 908 keypad ways
If you have a schematic, look for labels like KB_ROW and KB_COL. If you do not have a schematic, you must trace the lines manually.
| Symptom | Possible Cause | Fix Using Keypad Ways | |--------|----------------|------------------------| | Single key not working | Broken trace or dirty contact | Clean pad; jumper trace from keypad pad to next test point | | Entire row not working | Open row line | Trace row line from processor to first key, bridge broken way | | Entire column not working | Open column line | Similar – jumper column trace | | Multiple random keys | Short between ways | Check for solder bridge or corrosion |
The RM-908 uses a 4x4 matrix (4 rows, 4 columns) to scan 16 keys, though the phone has fewer physical keys. Unused matrix positions are left open. In mobile phone hardware terminology, "ways" refer to
| Fault Source | Prevention Method | |--------------|-------------------| | Liquid damage | Apply transparent conformal coating around the keypad connector after repair. | | Broken connector pins | Reinforce connector with a drop of epoxy (avoid pins). | | Cracked PCB near chassis screws | Do not overtighten screws; use plastic washers. | | Carbon debris shorting ways | Clean keypad dome sheet regularly with isopropyl alcohol. |
The Nokia 105 RM-908 uses a standard 5x4 or 4x4 matrix. Below is the typical logic mapping for this model. Note: Always verify with a multimeter in continuity mode as board revisions vary.
Rows (R1-R4) – Usually connect to IC pins via resistors. Columns (C1-C5) – Usually the input lines. When a "way" is broken (due to a
Typical Button to Matrix Mapping:
On the RM-908 board, the component responsible for scanning the keypad is typically a small CPU/IO expander or directly the main CPU. For keypad issues, we focus on the matrix lines at the CPU or a dedicated Keypad IC (often labeled U400 or similar near the keypad ribbon connector).
To avoid breaking the keypad ways in the future:
