Template:Repair Guide/Example: Difference between revisions

Repair Guide/Example
Device
Affects part(s)
Needs equipment
Difficulty
Type

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Latest revision as of 15:58, 28 September 2025

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Problem description

Symptoms

Symptom 1 (Figure 1)
Symptom 2

Solution

Diagnostic Steps

Repair Steps

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+{{stub}}
+{{Repair Guide
+|Device=
+|Affects parts=
+|Needs equipment=
+|Type=
+|Difficulty=
+}}
+== Problem description ==
+<!--
+Provide a concise description of the issue here. Be  as specific as possible to help readers quickly determine whether or not this is the exact problem they are facing.
+ -->
-'''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).
+[[File:Placeholder image.jpg|thumb|Example image (Figure 1) -- No image yet. Help expand this page by uploading it!]]
+== Symptoms ==
+<!--
+Detail all measurable or observable symptoms in this section.
+-->
+* Symptom 1 (Figure 1)
+* Symptom 2
-🔍 '''Step-by-Step Diagnosis'''
+== Solution ==
+<!--
+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.
-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:'''
+=== Diagnostic Steps ===
-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).
+=== Repair Steps ===
-'''Second attempt:'''
-Used a chip from MacBook A1278 (Unibody).
-🔴 Result: Severe input delay, no trackpad 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.
-'''⚙️ Technical Conclusion'''
-The U4801/U5701 keyboard SPI controller contains firmware/configuration specific to each board model. These chips are not freely interchangeable between different MacBook series (A1278, A1502, A1398, etc.).
-⚠️ '''Using an incompatible IC can cause:'''
-Reversed Caps Lock LED logic.
-Noticeable input delay on keys input.
-Malfunctions with the trackpad or power button.
-✅ '''Key Takeaway'''
-“The keyboard IC (U4801/U5701) must come from a firmware-compatible logic board. Although they are electrically identical, their internal configuration depends on the board model and its interaction with the SMC.”
-— Diógenes el Perro
-🛠️ Note: Neither the BIOS nor the SMC were reprogrammed during this repair.