Template:Repair Guide/Example: Difference between revisions

Revision as of 00:30, 3 August 2025

820-3662 NO NUMERIC KEYS/CAPS LOCK INVERTED/INPUT DELAY - TOUCHPAD ISSUES

The device arrived with the numeric keys on the internal keyboard non‐functional, despite a complete keyboard replacement. Visible moisture and sulfation were detected near the keyboard’s SPI controller (U4801).

🔍 Step-by-Step Diagnosis Visual inspection: Corrosion was found near the keyboard/trackpad controller area (U4801).

Voltage drop across R4814 (relevant resistor in the SPI circuit) was checked and confirmed expected values.

Chip replacement attempts: First attempt:

Replaced U4801 with a donor chip from board 820-3476 (MacBook A1502).

🟡 Result: Keyboard worked, but Caps Lock LED was reversed (lit when lowercase, off when uppercase).

Second attempt:

Used a chip from MacBook A1278 (Unibody).

🔴 Result: Severe input delay and overall poor keyboard behavior.

Final solution:

Replaced with U5701 from donor board 820-3332.

✅ Result: Keyboard fully functional, Caps Lock LED working properly, no delay, trackpad also fully operational.

@@ Line 4: / Line 4: @@
 The device arrived with the numeric keys on the internal keyboard non‐functional, despite a complete keyboard replacement. Visible moisture and sulfation were detected near the keyboard’s SPI controller (U4801).
-== Solution ==
+🔍 Step-by-Step Diagnosis
-<!--
+Visual inspection: Corrosion was found near the keyboard/trackpad controller area (U4801).
-If the issue has a single, specific solution, provide it in this section and delete the sub-headers below. Otherwise, if there are multiple potential causes for the problem, outline the process of identifying the root cause and offer corresponding solutions below.
--->
+Voltage drop across R4814 (relevant resistor in the SPI circuit) was checked and confirmed expected values.
+Chip replacement attempts:
+First attempt:
+Replaced U4801 with a donor chip from board 820-3476 (MacBook A1502).
-=== Diagnostic Steps ===
+🟡 Result: Keyboard worked, but Caps Lock LED was reversed (lit when lowercase, off when uppercase).
+Second attempt:
-=== Repair Steps ===
+Used a chip from MacBook A1278 (Unibody).
+🔴 Result: Severe input delay and overall poor keyboard behavior.
+Final solution:
+Replaced with U5701 from donor board 820-3332.
+✅ Result: Keyboard fully functional, Caps Lock LED working properly, no delay, trackpad also fully operational.