| Pin No. | Signal Name | Goes To (Component) | Function | |---------|-------------|---------------------|-----------| | 1 | KBR0 (Column 0) | CPU (Row Sense) | Keys: 4, 5, 6, * | | 2 | KBR1 (Column 1) | CPU | Keys: 1, 2, 3, # | | 3 | KBR2 (Column 2) | CPU | Keys: Left, Up, Down, Right, Call | | 4 | KBR3 (Column 3) | CPU | Keys: End/Power, Cancel/Back | | 5 | KBT0 (Row 0) | CPU (Column Drive) | Keys: 1, 4, Left, End | | 6 | KBT1 (Row 1) | CPU | Keys: 2, 5, Up, Cancel | | 7 | KBT2 (Row 2) | CPU | Keys: 3, 6, Down | | 8 | KBT3 (Row 3) | CPU | Keys: *, #, Right, Power | | 9 | GND | Ground | Common ground | | 10 | GND | Ground | Common ground | | 11-16 | NC / LED+ | Not connected / Backlight | Keypad backlight anode |

Save a high-resolution photo of a working Nokia 105 RM-908 motherboard’s keypad area. Use it as a reference to visually trace all KBR and KBT lines before starting any repair. Need more help? Leave a comment below or visit our forum for Nokia RM-908 schematic downloads and video tutorials.

(Note: Actual pin numbers may vary slightly depending on board revision; always test continuity with a multimeter before jumping.) Understanding the matrix helps you quickly diagnose which row or column has failed. Below is the standard mapping for the Nokia 105 RM-908 :

Here is the factory :

Remember: 90% of keypad way failures are either at the connector pins or within 2cm of the CPU. Methodical testing will save you hours of guesswork.

Unlike modern smartphones with capacitive touchscreens, the Nokia 105 RM-908 uses a traditional carbon-pellet or metallic dome switch matrix. When these fail, the solution isn’t always to replace the entire keypad flex cable; often, the issue lies in the motherboard’s (the copper traces and connection points between the processor and the keypad connector).