Tech Flashback: Apple Macintosh PowerBook 100 & Accessories

As it turns out, this week was a pretty good week for me. It’s not often something comes in, begging to be played with. It’s even less often that the object in question makes you drop almost everything so that you can play with it. This is one of those rare cases.

The story begins with a clean-up of a few labs at the uni. Drawers that have never seen the light of day for years finally get opened, and a black laptop bag is discovered. Luckily for me, a colleague and a good friend of mine was responsible for such finds, and recognized its significance and set it aside for me.

On Tuesday, 6th September, I visit the uni as I normally do, intending to meet with my supervisors and continue on with my writing work. On the way in, I have a chat with my friend, who gestures to the bag and says calmly, “take a look inside.”

A Piece of History – The PowerBook 100 (M1506)


If I’m to be honest, I am a bit young for this and as a “non” Apple user, I probably didn’t quite feel as much affection that some of the more mature readers might have. Despite this, I recognized it nonetheless as a piece of history. This was the second Macintosh laptop Apple had ever released. The first was the Macintosh Portable, largely unsuccessful with consumers due to its high price. The second was the PowerBook 100-series, consisting of the 100, 140 and 170 which were simultaneously launched in 1991 and the first to carry the PowerBook name.


Flipping the unit to its underside, we can see this one was a PowerBook 100, the smallest and cheapest of the PowerBook 100-series units. This particular unit was, as a result of that, quite successful at generating sales for its short 1-year life on the market. This particular unit was Made in Japan according to the label underneath, which was quite befitting as it was a Sony designed and manufactured product (in collaboration with Apple Industrial Design Group).

So far, it looks rather good, with only some light marks on the top and very slight yellowing of the plastic. However, it definitely shows its age, as all the rubber feet are disintegrating into goo, leaving marks and streaks on every desk that it sits on. That’s a very common thing, unfortunately.


Around the front, there is a slide latch that secures the lid to the base when stored or transported. The primary rechargeable battery is also inserted from the front, needing the cover to slide out to the right to release it from the body.


The left side has a few scratches, but houses the interrupt and power buttons. There are rotating plastic bits on the ends which are used as a “prop” to elevate the laptop slightly when on a bench for better cooling and keyboard feel. Unlike modern laptops, there are no fans or even ventilation slots for this unit.


The rear of the unit has a fold-down plastic flap which covers the I/O ports. On the left side is the power adapter input, an internal battery disconnect switch, an optional modem port (not installed, blanked out), Apple Desktop Bus (ADB) keyboard/mouse port, serial printer port, HDI-20 pin floppy drive port, HDI-30 external SCSI port and 3.5mm audio jack.


To the far right is a swing door that holds three CR2430 lithium coin cells. This is used to provide back-up power for the PRAM and for the main system PSRAM during battery changes, allowing for a “suspend to RAM” style operation making it faster to “wake” and get to work.


As expected, the cells have been around for so long that they’re likely to be dead. Two of them measured 245mV and 276mV respectively. The last had a barely acceptable 2.786V for some odd reason – suggesting the cells may have slightly mismatched capacities. They have failed bulged, with an odd “cracking” pattern around the back (rightmost cell shows it clearest) but to their credit, none of them leaked.


Opening up the lid shows a nice and clean 9″ passive FSTN monochrome LCD display with 640×480 resolution. There are potentiometer controls for contrast and brightness. A few slots have been cut to allow sound from its mono speaker to “escape”. A reduced keyboard layout is present, with clean keys and good travel. A 25mm trackball with two click buttons is provided as the pointing device.

The unit (manual specs) runs a Motorola 68HC000 16-bit CPU at 15.6672Mhz, with 2-8Mb of PSRAM, 256K ROM, 128 byte PRAM and 32K PSVRAM. It has a 20 or 40Mb SCSI hard drive as standard.

The Accessories

Having the unit is great, but the best part was that it had a nice complement of accessories.

Battery (M3053)


The PowerBook 100 battery is a pretty thin “slab”. On the top side, it is printed with warnings.


On the underside, it has two gold plated contacts marked positive and negative. There is no intelligence in the battery whatsoever. Unfortunately, the battery is a sealed-lead acid type with three 2V cells, which has short shelf life especially if unattended. These batteries are certainly dead due to the long term storage without periodic recharging, but at least none of their electrolyte had leaked and no corrosion is evident.


The front cover of battery is removable, and forms the fascia covering the battery slot on the laptop. It seems that someone prior had stressed the retainer clips, so they’re somewhat broken. However, if you’re modding your own battery or running without, it might be cosmetically preferable to cover the slot with the cover even if no battery is inserted into the bay.


Under the cover, there’s a few moulded codes in the plastic.


The contacts are recessed slightly for safety, but there’s really nothing else stopping accidental short circuits. Such design might not be passable nowadays due to our safety-centric and litigious society, as most batteries now have deeply recessed sockets instead of large contacts.


For those looking to modify or open the cells, it’s not entirely clear but I suspect the seal is around the plastic near the terminals. At a guess, the left most 1cm top might be broken away from the rest of the battery allowing the halves to be separated. Unfortunately, as lead-acid chemistries are unpopular for portable devices, and the form factor of this battery is much thinner than most lead-acid cells on the market, even a functional replacement is difficult.

Battery Recharger (M5140)


A common complaint from any laptop user is that they need more portable power, and they can’t wait around to charge it, so it was common to have charging stations and spare batteries. This unit had one spare, for a total of two batteries. The charger station had precisely two ports, so in theory one can have two batteries charging while working with the third.


Each slot has its own LED indicator light to show charging status.


The rear had vents for cooling the internal circuitry and a socket for the power supply to plug into.


The batteries were held in place by the two contacts at the end and friction. Nothing complicated, and indeed, no “smart intelligent” multiple-contact DRM-protected nonsense.


The charger itself had a model number of M3052, for use with M5140, rated at 7.5V at 2A. The feet on this unit are also disintegrating.

HDI-20 External 1.4MB Floppy Disk Drive


To make the unit small, and cheap, the floppy disk drive is an external unit which attaches via a HDI-20 connector with the end at the drive “captive”. This arrangement was not particularly convenient if you wanted to work with floppies on the move, but it did mean the main body of the laptop was smaller and lighter where you were working off the hard drive alone. It’s nice to see it’s a 1.4MB “high density” type drive, as data interchange with high density disks is much simpler as both IBM and Apple formats use MFM encoding.


Given that floppy disks were still a vital form of storage at the time, to make it an option sounds like a very strange decision.


The unit has a front door which protects the slot when not in use. Flipping it down allows for the drive to be accessed, with the door acting as a stand. As with most Apple 3.5″ drives, these featured an electronic eject mechanism to prevent “accidental” ejection during use.

PowerBook AC Adapter (M5140X)


To power the whole unit, you need a power adapter. As Apple were one early adopter of the switching power supply, the laptop is no different, utilizing a relatively large sized wall-wart style brick with a thick lead terminating in a 2.5mm barrel plug.


The unit is specified for 7.5V at 2A (15W) which really isn’t that much power. It’s interesting that when netbooks such as the eeePC launched, even those “low power” machines had 28W power adapters. This one has a universal voltage input with a positive polarity output. Two power adapters were included, as one was needed to run the charging station.

It also looks like the power adapters had changeable plugs, however, this is not the case. The plugs are not user serviceable and the plug “module” is kept captive by the case.

Apple Desktop Bus Mouse II (M2706)


This one isn’t strictly period correct, and seems likely to have been purchased 2 years later, but is an Apple Desktop Bus Mouse II. This was introduced in 1993, and its predecessor had a much less ergonomic “rectangular wedge” shape with a square button. As it’s an ADB interface, it can be plugged into the back of the laptop as an alternative to the internal trackball.


As can be expected, this is a classic “ball mouse”, requiring periodic cleaning of rollers to remove any trapped lint.

Who Owned/Used It?

This brings me to the question of who owned it, and who used it? Luckily for me, the unit had a lot of leads … no no, not power leads …


The front pocket of the bag had a stack of cards for this particular person, formerly a Research Engineer at CWWT (what has now become the Water Research Centre (WRC)). The numbers and name have been blacked out for privacy reasons, but it’s nice to see this card of a classic UNSW design, pre dating the Sydney-wide number change of “adding nine”, and domain as well, with Formerly, this might have been .oz until the introduction of .au as the ccTLD for Australia.

With a bit of sleuthing, I think I know where the former owner of this PowerBook 100 is … interestingly, not far away from the University in Mascot, if my hunch is correct.


It’s not often that computing technology from the early 1990’s is found in an undisturbed, almost pristine condition. Of course, the technology ages and so do the components, so getting things to work is probably not a walk in the park, especially when looking at other people’s experience. The good thing is that, at least from the outside, everything looks fine and dandy – no nasty corrosion, no big cracks or gashes, no strange-looking display, missing keys, etc. There’s a value in the aesthetic quality, even if there is a few scratches on one side. The color scheme is decidedly grey – which is probably nicer than the competing beige of that era. The included accessories really complete the package.

That being said, I’m not sure if aesthetic quality is enough for me. I want to see it do something. Anything. Even if that’s play dead.

About lui_gough

I'm a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!
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4 Responses to Tech Flashback: Apple Macintosh PowerBook 100 & Accessories

  1. matson says:

    Most important thing of all was to remove battery-ies. So CR coins rarely leak, but with that great imbalance, one cell could have eventually reversed the others, provoked leak.

    In a future experiment, you can observe behaviour of PowerBook battery power system: find maximum float/trickle voltage, and find minimum operating voltage (either: min. to power-on, point at which software is unstable, point at which system “gives out” sudden shuts-off).

    So those old PowerBooks use a 5.5/2.5 inlet: YAY! I knew the old ones used a DC barrel, but I never bothered to ask anyone to measure it. Yay, because 5.5 mm O.D. 2.5 mm I.D. seems to be _most common laptop power connector_.

    You might some day need to clean and re-lubricate floppy drive.

    That business card looks very nice.

    • lui_gough says:

      Hi Matson,

      Indeed, I agree with removing the batteries – already removed the replaced CR cells right away after finishing up as I had the Canon DM2500 organizer which did have a CR2032 cell leak and corrode its insides, which was not fun. It would probably mean the CR cells will live a few more years as they’re not getting drained by the internal RTC/PRAM/PSRAM.

      I could probably play around with the power, but I’m less inclined to do so because the machine is probably atypical. After so many years of storage, the capacitors are likely in poor shape, and with a replaced hard drive internally, the results aren’t necessarily representative of the bulk. The SCSI hard drive gives a terrible grinding noise, especially on an emergency head park (unexpected shutdown), so I really wouldn’t want to try it. At a guess, because it’s a sealed lead acid chemistry, the full charge voltage should be no more than 7.4V (2.4V/cell) (which probably explains the power adapter’s 7.5V) because this would be pretty close to the gassing point. The float should be about 6.8-6.9V for indefinite floating, as VRLA cells typically like no more than 2.3V/cell, although in better systems this is temperature compensated as well.

      That said, I’ve relubed a few floppy drives before – mostly 5.25″ drives along their stepper worm drive, so it’s no big drama, but I always feel it’s a bit of a shame to try to open up something especially when it looks in such good condition.

      – Gough

  2. Mark B. says:

    Gough, I think you just have to restore it. If I ever got such a device, it wouldn’t be collecting dust on a shelf before I repair it… or totally break it while attempting to repair. Old hardware is very fun to use, so I’d try my best to do anything reasonable to bring my device back to life. Yes, there probably isn’t a practical use for it now, but what would stop me from installing various interesting software, such as an ancient web browser (with a modem attached to the machine), some obsolete multimedia software, or an old file manager? I would be happy to read your articles about using it, as I like the Tech Flashback series very, very much!

    Keep up the good work!
    – Mark

  3. PitFo says:

    Hi Matson,

    Great project!

    I also have a PB100, batteries died long ago, but the PB could still boot.
    But this is a couple of years ago and inspired by your article, I fetched it from its storage in the loft and BANG! – It booted up, but no video. 8:(

    Now I need to also consider replacing critical capacitors and hope to get the device back to work.

    Great, I discovered that the 6MB memory expansion was already installed and the rare 14 Kbits/sec customized PB100 modem. I bought it in a fantastic Macintosh store in Columbus/Ohio and it was quite expensive these days.

    For me, the PB100 is really the good Mother of all Laptops, Notebooks, Ultrabooks and … yes, you name it! One of its biggest advantages was the passive LCD display, as you could work in super bright sunlight right at the pool or sitting in the cockpit of your sailboat!

    Last Weekend I bought a broken PB100 for 50€, combined both parts and got the video working. – Still a recap will be necessary. I did replace caps with 3 old Macintosh desktops with Tantalum ones in a successful manner. – Just be careful!

    Keep on with your enthusiasm and thanks for your guidance and inspiration!


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