Macintosh LC III and Performa 450: Difference between revisions
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==Known Issues== | ==Known Issues== | ||
=== Reverse Polarity Capacitor === | === Reverse Polarity Capacitor === | ||
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</gallery> | </gallery> | ||
: | ===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.<ref>[https://68kmla.org/bb/index.php?threads/macintosh-lc-iii-maxell-battery-damage-fixable.98/ "Macintosh LC III Maxell Battery damage - fixable?"] 68kMLA.</ref> '''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== | ==Original Parts== | ||
Latest revision as of 14:02, 27 November 2024
| This device is in the Bad Silk Screen category because it has mistakes from the factory that make the original silk screen unreliable. You may not be able to trust the original capacitor orientation polarities either. See the Known Issues sections for more details on what is wrong with this device. | 
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| This device is in the WorkNeeded:ReplacementParts category because it was flagged as missing information on replacement parts. If it has the original parts listed you may be able to search for replacements using the parametric searches available from parts distributors. If you have or make a list of replacement parts, please feel free to add them by copying the relevant table from EditorsToolbox:Tables | 
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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.
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
| 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
- ↑ https://www.downtowndougbrown.com/2024/11/the-capacitor-that-apple-soldered-incorrectly-at-the-factory/
- ↑ "Macintosh LC III Maxell Battery damage - fixable?" 68kMLA.
- ↑ "Capacitor Replacement". 68kMLA Wiki. Archived from the original on August 24, 2017. Content licensed under GNU FDL.