Nokia 105 Rm 908 Keypad Ways High Quality 〈Verified〉

For scraping away the top solder mask layer to expose hidden tracks. 3. Step-by-Step Diagnostic Process

Put the phone back together and test all keys. Conclusion

If the right column (3, 6, 9, #) is broken, the connection to the third column is broken.

: The power button has a specific red-coded supply line on technical diagrams. If the phone won't turn on, a jumper is often taken from the power section directly to the center point of the power key .

Use isopropyl alcohol to remove oxidation from the button pads.

Use a T5 screwdriver and plastic opening tools to carefully open the shell and expose the motherboard. nokia 105 rm 908 keypad ways

If a whole row or column is dead and there is zero continuity across the entire path on the board, the breakdown exists right at the filter component layer or under the CPU itself. Solder-Bridging the Filter Resistors

To identify where a connection is broken, use a multimeter set to .

CPU (MT6250) +-----------+ | | COL0 ---|P1.0 | COL1 ---|P1.1 | COL2 ---|P1.2 | COL3 ---|P1.3 | | | ROW0 ---|P2.0 |---10k---VIO (2.8V) ROW1 ---|P2.1 |---10k---VIO ROW2 ---|P2.2 |---10k---VIO ROW3 ---|P2.3 |---10k---VIO +-----------+

Anchor one side of the wire to the functional test point or key pad. Route the wire carefully around the board layout to avoid screw holes or housing clips, then solder the remaining end to the non-functioning key pad.

Clean whole board with IPA; reflow CPU gently if experienced. Broken inner ring track path Jumper the inner circles of the dead column together. Specific Row Broken outer ring track path Solder a wire connecting the outer rings of the dead row. Power Button Only Corrosion on upper trace For scraping away the top solder mask layer

do not operate on separate lines. Instead, they share a matrix consisting of and inner copper pads (centers) . Each key requires a connection to both a horizontal row and a vertical column to register a press. When a group of keys fails at the same time, it points to a specific break in that row or column line. Common Keypad Groupings (Trace Lines)

[Key Center Pad] <======= Enamel Jumper Wire =======> [Working Node/Test Point] The Power Key Jumper Solution

Let the motherboard cool completely to room temperature before inserting a battery to test the buttons again.

Set your hot air rework station to roughly with an air velocity setting of 3 .

Each key has an inner point (signal) and an outer ring (ground/common). Conclusion If the right column (3, 6, 9,

Note: You can set the phone to ask for a security code to protect your privacy and personal data. The pre-set code is 12345. Nokia 105 User Guide: Keypad - HMD

If you get a valid GR reading on one side of the resistor but an Open Line ( OL ) on the side facing the keypad, the resistor is blown.

Ensure your jumper wires are properly enameled (insulated). If the bare copper touches the wrong section of the board, it can cause keys to become permanently "stuck" or auto-press.

Each column line to keypad pad: series 220Ω resistor (R200–R203). Each row line to keypad pad: direct connection, but pull-up at CPU side.