Macintosh Plus
The Macintosh Plus was the successor to the original Macintoshes. It was released in 1986, with its main new features being built-in SCSI, expandable RAM, and an internal 800K floppy drive.
Specifications
| Spec | Details |
|---|---|
| Release Date | January 1986 |
| Discontinuation Date | October 1990 |
| Processor | Motorola 68000 @8MHz |
| RAM | 4x 30-pin SIMM Slots - 1MB Standard - 4MB Maximum |
| Hard Disk | None |
| Display | 9-inch Monochrome CRT Display @512x342 |
| Audio | Internal Speaker |
| Internal Drives | Auto inject 3.5" 800KB Floppy Drive |
| Expansion | None |
| Networking | None |
| Other I/O | - 2x Serial - 1x DB25 SCSI - 1x External Floppy Port - 1x Keyboard connector - 1x Mouse connector - 1x Line Out |
| PRAM Battery | PX21 4.5V Alkaline |
| Original Mac OS | System 3.0 |
| Maximum Mac OS | Mac OS 7.5.5 |
Upgrades
CPU Upgrades
Faster 68000, 68020, and 68030 upgrade boards were made for the Mac Plus.
Resources
 Service Manual |
 Logic Board Schematic |
Power Supply Schematic |
|---|
Common Faults & Maintenance
PRAM Battery Leaks
The Alkaline PRAM battery in the Plus is very prone to leaking and should be removed. It is located behind a door on the back of the system. A leak can cause damage to the analog board it is attached to.
Capacitors
The Plus capacitors have held up pretty well over time, but they're old enough now that the analog boards often need recapping. The logic board rarely has capacitor trouble.
No Video Defect
Due to having no internal fan, the Plus gets pretty toasty when its running. This often causes the larger solder joints on the analog board to crack, causing a no video defect. I would recommend reflowing the large solder joints on the power connector and flyback transformer even if your Plus works fine, for additional stability.
Floppy Drive Failure
The Plus floppy drive often needs cleaning and relubrication to work correctly. In addition, there is a gear inside the eject motor that can fall apart with age. If your floppy drive won't eject disks, this is likely the cause, and replacements are readily available online.
Page last updated (MM/DD/YYYY): 03/03/2025
Update Reason: page created
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