Macintosh Portable
The Macintosh Portable was Apple's first truly portable mac. It took the form of a luggable, with a high-quality Active-Matrix LCD, a full-size keyboard, and a large lead-acid battery. All of these features did cause it to be very heavy, and very expensive. The original Portable did not have a backlit LCD. An early 1991 refresh added a backlight, which cut the battery life in half!
The portable is unique for being just about the only vintage mac that doesn't turn yellow - except for the space bar.
Specifications
| Spec | M5120 (Non-Backlit) | M5216 (Backlit) |
|---|---|---|
| Release Date | September 1989 | February 1991 |
| Discontinuation Date | February 1991 | October 1991 |
| Processor | Motorola 68000 @16MHz | |
| Bus Speed | 16MHz | |
| RAM | Proprietary - 1MB Soldered - 8MB Maximum |
Proprietary - 2 or 4MB Standard - 8MB Maximum |
| Hard Disk | Proprietary connector using the SCSI Bus - None or 40MB Standard |
|
| Display | 9.8" Non-Backlit Active Matrix Monochrome @640x400 | 9.8" Backlit Active Matrix Monochrome @640x400 |
| GPU | Unknown | |
| Main Battery | Sealed Lead Acid | |
| PRAM Battery | Standard 9V Battery | |
| Power Supply | Barrel Jack - 7.5V 1.5A - Apple M5136 |
|
| Disk Drives | 3.5" 1.44MB Floppy Drive | |
| PC Cards | None | |
| Networking | Serial Modem Connector | |
| Other I/O | - 2x Serial - 1x ADB - 1x DB25 SCSI - 1x Proprietary Video Out (uses VGA connector but isn't VGA) - 1x Ext. Floppy Connector - 1x Line Out |
|
| Pointing Device | Trackball | |
| Minimum Mac OS | System Software 6.0.4 | System Software 6.0.8 |
| Maximum Mac OS | System Software 7.5.5 | |
Resources
 Service Manual |
Capacitor Reference (M5120) | Capacitor Reference (M5126) |
|---|
Common Faults & Maintenance
The Macintosh Portable is one of the single most unreliable Macintoshes ever made.
It has the usual suspect: bad capacitors, but also so much more. Don't fret! Getting a portable running will be worth it in the end.
List of common issues:
Everything that goes wrong on the portable. (Commonly at least).
- Failing and Leaking SMD Capacitors
- It won't start without a working main battery
- The Power Supply fails
- The Hybrid IC is extremely suceptible to corrosion, and it's right next to some bad caps on the board.
- The hard drive is nearly always dead.
- The displays are prone to failure as well.
Here are all of those issues, in order, in detail.
Bad Caps
Like other Macs released at the time, the main board on the Portable has surface-mounted electrolytic capacitors. They are extremely prone to failure and when they fail, they leak a corrosive fluid onto the board that damaged components, especially the fragile Hybrid IC (more on that later). They will all need to be replaced before the portable should be operated.
Batteries Required!
The Mac Portable requires that both the main Lead Acid battery, and the secondary 9V battery are installed and working for the portable to start. Due to the power manager's (poor) design, it cannot run off of the charger alone. It will always run off of the battery, regardless of whether or not the system is plugged in. Luckily, rebuilding the battery is easy, and there are portable-designed batteries available for purchase if you don't want to rebuild one yourself. Also, being a lead acid battery, don't let it go dead, or it will die, just like a car battery would. The secondary battery is easy, it just uses a standard 9V battery, just like the one in your smoke detector.
There also now exists a battery eliminator that goes in place of the battery, and allows the Portable to run without one.
But you can just use a PowerBook charger, right?
No, you cannot, and doing so will damage the Portable's logic board.
The Portable's power manager is very strange and poor design. The power manager only takes a voltage reference at the battery's circuit, rather than at the DC Input. Due to this, if you run a Portable only from the AC Adapter, the power manager is unable to properly regulate voltage, and the laptop's power rails will run out of spec. When it goes far enough out of spec, ICs get damaged. This design worked fine when new because Apple shipped the Portable with a current-limited 1.5A AC Adapter, which cannot deliver enough current to run the portable without the battery installed. This is why the Portable needs a working battery to start up. The later gray PowerBook AC Adapters are rated for 2A, and this is enough current to boot the portable without a battery. But if you don't have a battery installed, it cannot properly reference the voltage, and then you're in trouble.
If you don't want to bother with the upkeep of a lead acid battery, you can now purchase a battery eliminator, which is a capacitor bank which goes in place of the battery. This allows you to run the Portable from the AC Adapter alone.
Unreliable Power Supplies
What I've just said should tell you that you will need an original supply (or compatible replacement of the same exact spec) to run a portable. They're pretty unreliable though, due to (you guessed it) bad caps. Portable supplies should also be recapped before you use it for long.
Hybrid Module Failure
The Hybrid IC is that weird blue thing in the bottom left corner of the board. It is only found on the M5120 Non-Backlit models. It generates the 5 and -5 volt rails for the portable (other stuff too maybe? I'm unsure). The Hybrid is made of a ceramic substrate, and part of its design includes resistors that are basically printed or embedded on the substrate itself. Unfortunately, these resistors are easily damaged by corrosion, which causes the Hybrid module to stop working correctly. Unfortunately, the Hybrid module is located right next to a row of leaky capacitors. As a result, the Hybrid is becoming a very unreliable part nowadays.
A common failure mode which is caused by a failing Hybrid is that when booted to the desktop, the Portable will immediately display a low battery warning and shut off, regardless of whether it is connected to power or not.
Thankfully, the Hybrid module has been reverse-engineered and replacements are readily available. You can get a newly-made Hybrid from Joe's Computer Museum.
Hard Drive Failures
The hard drive in the Portable is quite unreliable, which is relatively common for drives of this time, but they can be pretty easily fixed (most of the time), so it's worth putting here. First of all, it uses a special SCSI connector that requires an adapter if you want to install a standard drive or solid state device. The drive is manufactured by Connor Peripherals, and it suffers from the usual suspects of the time: Melting rubber. These drives often use a rubber bumper on the head assembly, which goes sticky, and causes the heads to get stuck. The portable drive is no exception. It's pretty easy to fix though, just open the drive up and tape over the rubber. The data density in these is low enough that it shouldn't kill the drive to open it, unless you open it inside of a woodshop or something.
That isn't all - the drive's rubber seal also melts! This can cause the seal to quite literally leak around the drive, and if it contaminates the platters, it's toast. To fix this, you should remove the old seal and either replace it, or simply seal the drive a different way, such as using tape. As long as the drive is sealed it should work.
Display Failure & LCD Tunnel Vision
There isn't really much to say here. The displays in both models of the portable just die sometimes. Bad pixels, bad lines, etc. There isn't much that can be done, unless the issue is with the display cable, which does also happen.
Being an Active Matrix Monochrome LCD manufactured by Hosiden, the Portable's LCD is susceptible to the LCD Tunnel Vision problem. Intrestingly enough though, the Portable's LCD seems to be affected by this issue far less than later model laptops with those panels.