Macintosh LC III and Performa 450

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Macintosh LC III and Performa 450
Preliminary Information
Release Year 1993
Leak Risk High
Batteries Yes, Potentially Destructive
Mounting Technology Through Hole (PSU), SMD (Logic Board)
Capacitor Types Aluminum Electrolytic
Destructive Entry No

The Macintosh LC III (also branded as the Performa 450) was sold by Apple Computer from February 1993 to February 1994. Like all Macintoshes of its era, its original surface-mount electrolytic capacitors leak their contents and require replacing for both functionality and to protect critical traces on its circuit board from being eaten by electrolyte.

Known Issues

Reverse Polarity Capacitor

Causes
Apple designed the mainboard incorrect with the polarity of C22 being reversed because it is a negative voltage rail.[1]
Solutions
The original capacitor should just be removed if it is still installed. When replacing a capacitor be sure to install C22 OPPOSITE to the PCBs marked polarity.
  • Capacitor C22 is located next to the blue wire on the power connector in the corner of the main board.
    Capacitor C22 is located next to the blue wire on the power connector in the corner of the main board.

    • Maxell Battery "Bombs"

    Causes
    Apple placed a small lithium battery on the Macintosh LC III/Performa 450's Logic Board to power and preserve the contents of the Parameter RAM (PRAM). Apple used a number of different brands of battery for this purpose, one of which is Maxell. Maxell lithium batteries are notorious for rupturing in storage and spewing its highly corrosive contents all over the board.[2] If your Macintosh LC III/Performa 450 is still intact with its original PRAM battery, THE BATTERY MUST BE REMOVED IMMEDIATELY, even if it is not Maxell brand.
    Solutions
    Macintosh LC IIIs/Performa 450s with exploded PRAM batteries are pretty much irreparable, save for replacing the entire Logic Board.

    Original Parts

    Revision 820-0650-A Logic Board

    Capacitor Specifications and Footprint Information[3]
    RefDes Qty Capacitance (µF) Voltage (V) Mount Size Type Brand
    C8, C19, C20, C21, C22 5 47 16 SMD Aluminum Electrolytic Unbranded
    C2, C4, C5, C7, C18 5 10 16 SMD Aluminum Electrolytic Unbranded
    C13 1 100 6 SMD Aluminum Electrolytic Unbranded

    References

    1. ↑ https://www.downtowndougbrown.com/2024/11/the-capacitor-that-apple-soldered-incorrectly-at-the-factory/
    2. ↑ "Macintosh LC III Maxell Battery damage - fixable?" 68kMLA.
    3. ↑ "Capacitor Replacement". 68kMLA Wiki. Archived from the original on August 24, 2017. Content licensed under GNU FDL.
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