{"id":3293,"date":"2022-06-17T12:22:28","date_gmt":"2022-06-17T11:22:28","guid":{"rendered":"https:\/\/www.quantum-bits.org\/?p=3293"},"modified":"2022-08-24T09:59:57","modified_gmt":"2022-08-24T08:59:57","slug":"on-retro-computing-macintosh-plus","status":"publish","type":"post","link":"https:\/\/www.quantum-bits.org\/?p=3293","title":{"rendered":"On retro-computing: Macintosh Plus"},"content":{"rendered":"

I am an Apple<\/a> Fanboy. Always been. Nevertheless, it took me a long time to actually own an Apple device. The first Mac I ever bought was a 12″ PowerBook G4<\/a>, in 2003. Since then, I went down the rabbit hole, with a 3rd generation iPod<\/a> (2003), a Mac Mini G4<\/a> (2005), a 4th generation iPod nano<\/a> (2006), a first generation iPhone<\/a> (2007), an iPhone 3G<\/a> (2008), a first generation MacBook Air<\/a> (2008) and so on. By now, the apartment is now filled with Apple hardware, including an iPad pro<\/a>, 2 Apple TV<\/a>s, 4 HomePods<\/a> and HomeKit<\/a> devices in every room.<\/p>\n

I am, at this very moment, typing this text on a MacBook Pro<\/a>, listening to music on AirPods Pro<\/a> and wearing an Apple Watch<\/a> at the wrist. Yes, all this is probably insane.<\/p>\n

The first Apple computer I ever touched was an Apple II+<\/a>, in 1982 if memory serves. It had been brought at school by the father of one the students, and, being nerdy, I had the chance to be one the selected few to get access to it. Nice memories.<\/p>\n

But the one I dreamed of in the late 80’s was – of course – the Macintosh<\/a>. So damn cool. And so damn expensive. Then, years and years later … I caught the vintage computer fever. And MARCHintosh2022<\/a> was coming. What the hell, why won’t I make that dream come true ?<\/strong><\/p>\n

\"\"<\/p>\n

First encounter with a Macintosh Plus<\/span>
<\/strong><\/p>\n

I remember quite well my first real-life encounter with a Macintosh Plus<\/a>. It was in 1987, I was 16 and I managed to get a free ticket to the Infora<\/strong> expo. It was my first computer expo, and I preciously kept that ticket :<\/p>\n

\"\"<\/p>\n

I took the bus to get to Eurexpo<\/a>. The boring PC part of the expo was … well … boring. I happily skipped this part to went straight to a Silicon Graphics IRIS<\/a> (1000 or 2000 series, I can’t remember) stand were they were demonstrated. Unix\/IRIX, 3D, real-time computing. Now, that was something !<\/p>\n

And then … next to these amazing workstations, there was a stand filled with 4 or 5 Macintosh Plus. For some reasons, everyone could get hands-on with them. One of them was running MacPaint<\/a>. Oh boy, I was hooked ! I went home and started writing a MacPaint clone … for my Amstrad CPC<\/a>. It took me a couple of months. It wasn’t that bad, though using a joystick and arrow keys instead of a mouse wasn’t the best user experience ! By 1988, I had pushed my trusty Amstrad to its limits, and since there was no way I could afford a Macintosh, I bought a Jackintosh<\/a> instead.<\/p>\n

35 years later, it was about time I got a Macintosh Plus !<\/p>\n

Sourcing a Mac Plus<\/span><\/p>\n

Since I was happy with both Sinclairs (ZX81<\/a> and Spectrum<\/a>) and the Amstrad<\/a> CPC 464, I went straight to Leboncoin<\/a> web site. It wasn’t easy to find a proper offer. Most of them were madly overpriced<\/strong>. Some Macs were in (very) bad shapes and\/or incomplete. Some were obvious scams (wrong keyboard, wrong mouse, major differences between pics and descriptions, …). Most of them had to be handpicked 100’s of kilometers from where I live (I don’t drive). In the end, after 2-3 weeks of intense researches, I settled for an offer with a reasonable price (250\u20ac, including shipping). A week later, I received this package:<\/p>\n

\"\"<\/p>\n

Unboxing and first boot<\/span><\/p>\n

I was very worried about the shipment<\/strong>. But the Mac Plus came neatly packaged, with no apparent signs of anything broken: <\/p>\n

\"\"<\/p>\n

I had to make sure<\/strong>. Even though it was most certainly unsafe<\/strong> (since nothing was checked yet), I plugged the Mac in and pushed the power button on.<\/p>\n

Crossing fingers. No magic smoke. Good. I was greeted by the “Bong” startup sound. That’s a good start. And no sad Mac<\/a>. Nice<\/strong> !<\/p>\n

The screen turned gray. Yeah !<\/strong> The Mac booted up to the point where it needed to load MacOS, displaying a 3 \u00bd-inch floppy disk with the usual blinking question mark:<\/p>\n

\"\"<\/p>\n

The internal floppy disk drive started making creepy noises<\/strong>. A few seconds later, the Mac displayed a floppy disk with a blinking cross<\/strong>, as pictured here:<\/p>\n

\"\"<\/p>\n

Not good<\/strong>, since there was no disk inserted. The blinking cross is displayed whenever the drive cannot read a disk. I was expecting the question mark to keep blinking. There is probably something wrong with the floppy disk drive<\/strong> …<\/p>\n

On top of the noise coming from the drive, there were also funky electrostatic noises<\/strong> (but no sparks), coming out of the case. I was suspecting something could be wrong with the flyback transformer<\/a>. But no ozone smell<\/strong>. I shook the case a bit, slapped (gently) on both sides of the case. Still, the screen was very stable. A screen going on and off while slapping the case could have been a sign of bad connections or cracked solder joints on the analog board.<\/p>\n

At least, the CRT wasn’t broken during the shipment, which was my major concern. The mouse also seemed to be working fine. I switched off the Mac. Time for inspection !<\/p>\n

Decoding the serial number<\/span><\/p>\n

From the outside, this Mac seemed in good conditions. No scratches, nothing obviously broken. But very, very, very dirty<\/strong>.<\/p>\n

On the back of the case lies a sticker with a serial number, reading “C714082M0001AP”:<\/p>\n

\"\"<\/p>\n

This serial number can be decoded using this script: http:\/\/macfaq.org\/serial.html<\/a><\/p>\n

It returned: “Your European Macintosh Plus (M0001AP), with serial number C714082M0001AP, was the 274th manufactured during the 14th week of 1987<\/strong>“.<\/p>\n

The plastic case had yellowed, so it is hard to tell. But, judging by the date of manufacturing, this Mac Plus was most probably a Platinum<\/strong> one, and not an early beige (aka Pantone 453) one. The mouse is much more yellowed though, so it might be an older mouse and might have belonged to an older beige<\/strong> Mac.<\/p>\n

Opening up the Mac<\/span><\/p>\n

Opening up and fully disassembling a Mac Plus is a tedious process<\/strong>. Before anything, make sure the Mac is unplugged<\/strong>.<\/p>\n

Let’s start from the back of the case, and let’s open the PRAM battery compartment:<\/p>\n

\"\"<\/p>\n

Gosh, the battery was still there<\/strong> ! I promptly removed it. But there were only very little signs of corrosion<\/strong>. That was (somewhat) a relieve.<\/p>\n

The next thing to do is to remove the screw on the top of the battery compartment<\/strong> with a Torx T15 screwdriver<\/strong>. Then, with the same screwdriver, you will have to remove the two black screws<\/strong> at the bottom of the case:<\/p>\n

\"\"<\/p>\n

Then comes a first tricky<\/strong> part: removing the screws from the top, under the handle<\/strong>. For this, you will either need a very long<\/strong> screwdriver or, as I did, use an extension<\/strong>:<\/p>\n

\"\"<\/p>\n

Once unscrewed, don’t forget to remove the programmer switch on the side of the Mac<\/strong>. It you don’t, since it is reaching inside of the case for push buttons on the PCB, it can break<\/strong> while separating the front and the bottom parts of the enclosure:<\/p>\n

\"\"<\/p>\n

Once removed, the Mac case can be opened, separating the front bezel from the rear housing:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

The PCB you see in the back is the analog board<\/strong>. It powers<\/strong> the main board (which lies underneath the metal chassis). It also powers<\/strong> and drives<\/strong> the CRT<\/strong>. The analog board is protected on its side by this insulator plastic sheet:<\/p>\n

\"\"<\/p>\n

Let’s have an overall look inside. It is extremely dirty<\/strong>. Everything here is filthy<\/strong>, covered with black<\/strong> and sticky<\/strong> dust<\/strong>. It doesn’t seem to be some kind of burn artifact though. Cables are utterly sticky.<\/p>\n

\"\"<\/p>\n

Removing the logic board<\/span><\/p>\n

To remove the logic board, first, will have to pull free the floppy<\/strong> disk drive ribbon<\/strong>:<\/p>\n

\"\"<\/p>\n

Then, you will have to do the same with the harness<\/strong> of the main connector:<\/p>\n

\"\"<\/p>\n

Next, you will have to slide off the protecting shield<\/strong>, underneath the logic board:<\/p>\n

\"\"<\/p>\n

Finally, you can gently slide the logic board off the chassis<\/strong>:<\/p>\n

\"\"<\/p>\n

Discharging the CRT<\/span><\/p>\n

To be safe, before doing anything related to it, it is important to discharge the CRT<\/strong>. The first thing is to make sure you have unplugged<\/strong> the Mac. Then, take off any jewellery or anything metallic from your hands<\/strong>. During the next steps, make sure to work with only one hand<\/strong>. You don’t want to have two hands in when working with high voltage.<\/strong> If anything goes bad, the current, taking the path of least resistance, would flow from one hand to the other, passing straight to you chest, where lies your heart<\/strong>. For the same reason, don’t use a grounding strap while discharging the CRT<\/strong>. Wearing rubber<\/strong> soled<\/strong> shoes<\/strong> if also a good<\/strong> precaution<\/strong>. It is also good to have someone around,<\/strong> who could take actions (first aid, calling emergencies, …) in case something would go wrong. <\/p>\n

The next step it to attach one side of an alligator clip to a flat head screwdriver<\/strong>, the other side being attached to the ground<\/strong>, as pictured in the above photo<\/strong>. Make sure that the screwdriver has a good insulated handle<\/strong>.<\/p>\n

Then, you will have to carefully slide the end of the screwdriver under the anode suction cup<\/strong>. You will to push far enough to make contact with the prongs<\/strong> under the anode cup. This will discharge the CRT<\/strong>. You might hear<\/strong> or even see<\/strong> a spark. In any case, hold 5 seconds to make sure it is fully discharged<\/strong>.<\/p>\n

\"\"<\/p>\n

Once, and only once it is done, you are safe to go<\/strong>. You can push sideways until one of the prongs is released, then you can pull free the suction cup:<\/p>\n

\"\"<\/p>\n

As you can see, this anode cup is oily<\/strong> and very sticky<\/strong>.<\/p>\n

Removing the analog board and the CRT<\/span><\/p>\n

The next step to remove the analog board and the CRT themselves from the chassis. First, you will have to pull free the connector going from the analog board to the neck of CRT<\/strong>:<\/p>\n

\"\"<\/p>\n

Then, you can unscrew both grounds<\/strong>:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Now, you can unscrew the analog board<\/strong> from the chassis:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

You will now have enough space to reach for the other analog board to CRT connector and pull it free<\/strong>:<\/p>\n

\"\"<\/p>\n

You can now remove the analog board<\/strong>. It is an easy task to remove the last screws<\/strong> of the front bezel<\/strong> and separate the CRT from the case<\/strong>:<\/p>\n

\"\"<\/p>\n

During these step, handle very careful the CRT<\/strong>. The neck is especially fragile<\/strong>. In the end, I put the CRT safely on a old towel<\/strong>:<\/p>\n

\"\"<\/p>\n

Removing the chassis and the disk drive<\/span><\/p>\n

The next steps are fairly easy ones. First, take care of the last screws on the front bezel<\/strong>, to set the chassis free:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Once the front panel is freed, you can remove the Apple logo<\/strong> to keep it safe, pushing<\/strong> with a pin<\/strong>:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Now, you can take care of the internal drive shield<\/strong>, removing these four<\/strong> screws<\/strong>:<\/p>\n

\"\"<\/p>\n

The metal chassis is now free (and, according to the markings, was built in the end of March 1987):<\/p>\n

\"\"<\/p>\n

Finally, you can set free the disk drive itself, removing four<\/strong> golden<\/strong> screws<\/strong> on the sides: <\/p>\n

\"\"<\/p>\n

And … that’s it ! The Mac case is now completely disassembled<\/strong>:<\/p>\n

\"\"<\/p>\n

Time now to open up the mouse and the keyboard.<\/p>\n

The mouse<\/span><\/p>\n

The mouse itself is of a different shade of yellow than the case and the keyboard. The color of the button is also different from the color of the keys.<\/p>\n

\"\"<\/p>\n

My hypothesis is that this mouse belonged to another older Mac Plus<\/strong> (not a Platinum Mac Plus, but a beige<\/strong> one). If am I correct, later mouses were made in Japan, the earlier ones (beige) being made in USA. Furthermore, the round “hatch” is black for beige ones, while it is grey for Platinum ones. On the back of the mouse, a number “2” sign was added using a blue marker. All this somehow corroborates the hypothesis …<\/p>\n

\"\"<\/p>\n

To open the mouse, simply remove the two<\/strong> black<\/strong> screws<\/strong> from the top and open<\/strong> the<\/strong> case<\/strong> with the help of a plastic prying tool:<\/p>\n

\"\"<\/p>\n

The button is easily removed (beware of the spring<\/strong> nevertheless). Inside the case there is a small PCB and the mechanical parts of the mouse:<\/p>\n

\"\"<\/p>\n

The ball itself can be freed, turning left the round “hatch” :<\/p>\n

\"\"<\/p>\n

There is only one screw left<\/strong> to be removed:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

There we go, this mouse is ready to be cleaned !<\/p>\n

\"\"<\/p>\n

The keyboard<\/span><\/p>\n

Overall, the keyboard is in decent shape, though extremely dirty, like the other parts of this Mac. It has a very crunchy<\/strong> feeling. Somehow, the case is a little twisted and couldn’t lie totally flat<\/strong> on the table. Let’s crack it open !<\/p>\n

\"\"<\/p>\n

To do that, remove the cable, flip the keyboard and remove the six screws<\/strong>:<\/p>\n

\"\"<\/p>\n

Once done, it is easy to extract the keyboard from it case:<\/p>\n

\"\"<\/p>\n

As expected, the inside is filled with dust bunnies<\/strong>, gunk<\/strong>, hair<\/strong> and dead<\/strong> insects<\/strong>:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

I started removing the key caps<\/strong> with the help of a key<\/strong> remover<\/strong>. In the end, none of them were broken<\/strong>, though there were probably some kind of soda or coffee spillage on them at some time in the past:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

The amount of dust explains the crunchy feeling. None of the plungers were broken or stuck<\/strong>:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

I could have fully disassembled the keyboard to get access to its PCB<\/strong>. But this is a tedious<\/strong> and probably risky<\/strong> process. It involves a lot of desoldering<\/strong> (at least two per key, on the back of the PCB) and, for each of them, pushing a snap mechanism which might break if the plastic were to be brittle<\/strong>. Since the PCB and the mechanisms seemed more than OK, I didn’t bother getting into this process. Crossing fingers. Testing the keyboard in the end will tell<\/strong> ! <\/p>\n

Cleaning the keyboard<\/span><\/p>\n

I let the key caps soak into soapy<\/strong> water<\/strong> for quite some time. Meanwhile, I started vacuuming<\/strong> the keyboard:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Then, using a toothbrush<\/strong> and soapy<\/strong> water<\/strong>, I cleaned the top part of the keyboard:<\/p>\n

\"\"<\/p>\n

Once done, I cleaned the back of the PCB<\/strong> with some IPA<\/strong>:<\/p>\n

\"\"<\/p>\n

After letting the keys into soapy water for a couple of hours, cleaned each key one by one with a micro-fiber cloth<\/strong>, let them dry and then started putting back the keyboard:<\/p>\n

\"\"<\/p>\n

In the meantime, the keyboard cable<\/strong> was taking a much need bath<\/strong>:<\/p>\n

\"\"<\/p>\n

And so were the bottom<\/strong> and top<\/strong> parts of the keyboard case:<\/p>\n

\"\"<\/p>\n

Cleaning the case<\/span><\/p>\n

Just like the keyboard, all parts of the case took a bath<\/strong>, followed by a thorough scrubbing<\/strong> with a toothbrush<\/strong>:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

You can judge by the color of the water how filthy<\/strong> it was !<\/p>\n

\"\"<\/p>\n

Once cleaned and dried, I could, at last, read the famous signatures engraved inside the back of the case<\/strong>:<\/p>\n

\"\"<\/p>\n

Finally, I took care of the analog board insulator<\/strong> sheet<\/strong>:<\/p>\n

\"\"<\/p>\n

Then it was time to clean the motherboard shield<\/strong>:<\/p>\n

\"\"<\/p>\n

Cleaning the mouse <\/span><\/p>\n

The mouse took a soapy bath<\/strong>, and was scrubbed<\/strong> with the help of a toothbrush<\/strong>:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

I finished this part cleaning the ball with a soft cloth<\/strong>.<\/p>\n

Cleaning the CRT<\/span><\/p>\n

Cleaning the plastics was an easy job. Cleaning the CRT was something else<\/strong>. Oh boy, it was absolutely<\/strong> disgusting<\/strong> :<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

I took me quite some times and efforts, using WD40<\/strong>, IPA<\/strong> and window<\/strong> cleaner<\/strong>.<\/p>\n

\"\"<\/p>\n

But in the end, I was very, very pleased<\/strong> with the results !<\/p>\n

\"\"<\/p>\n

A disk drive in poor shape<\/span>
<\/strong><\/p>\n

From the first boot attempt, I was expecting some troubles with the floppy disk drive<\/strong>. On first inspection, nothing really alarming at the mechanical level, apart from being dirty<\/strong>:<\/p>\n

\"\"<\/p>\n

The first thing to do is to carefully unhook both springs<\/strong> on the sides of the floppy disk drive:<\/p>\n

\"\"<\/p>\n

Once done, and once the black piece of plastic holding the head was removed<\/strong>, you can separate<\/strong> the top part, giving access to the inside<\/strong> of the drive:<\/p>\n

\"\"<\/p>\n

These parts were cleaned with WD-40<\/strong> and q-tips<\/strong>:<\/p>\n

\"\"<\/p>\n

I then cleaned<\/strong> the head<\/strong> with IPA<\/strong> and a chamois swab<\/strong>:<\/p>\n

\"\"<\/p>\n

Apple floppy disk drive are very peculiar<\/strong> devices. First, to reach 800Kb (instead of the usual 360Kb per side for usual single density 3″\u00bd disks at the time), Apple used a variable speed rotation<\/strong> trick, so that they could put fewer sectors on the smaller inner tracks and more sectors on the wider outer tracks of the disk. To do that, the disk speeds up when accessing the inner tracks and slows down when accessing the outer ones<\/strong>. That is a neat trick, but I makes it impossible<\/strong> to use regular floppy disk drive to write disks for Macs of this era, since “normal” drives are using a constant speed. That is problematic nowadays to create disks for Mac 128\/512\/Plus<\/strong>.<\/p>\n

Second, the eject<\/strong> mechanism<\/strong> is motorized<\/strong>. There is no eject button per se<\/em>. Well, mechanically speaking, there is one, but it is not user accessible: you have to use a pin or a paper clip to push it through a tiny little hole on the right side of the disk slot. The eject mechanism is software<\/strong> driven<\/strong>. From the finder, if one drags and drops the Floppy icon to the Trash icon, the disk is ejected via a motorized mechanism. Neat, but … very fragile : remember how the disk drive was making weird noises when the Mac tried to boot up.<\/p>\n

Let’s open up the motor<\/strong> compartment<\/strong> of the eject<\/strong> mechanism<\/strong>:<\/p>\n

\"\"<\/p>\n

Inside the motor compartment, there is a series of four gears<\/strong>. As expected from the noise, they were stuck<\/strong> …<\/p>\n

\"\"<\/p>\n

I used WD-40 lithium white grease<\/strong>, and carefully removed<\/strong> each<\/strong> gear<\/strong>:<\/p>\n

\"\"<\/p>\n

Unfortunately, the last one immediately broke into pieces<\/strong>. It is a well known phenomenon. This piece is not made of the same material as the other ones. It is actually designed to easily break<\/strong>, in order to protect the motor in case of problems. But, as times goes, this little gear can get stuck (lack of grease, etc.) and … literally explodes as soon a you try to remove it.<\/p>\n

Arm is done<\/strong>. I will have to change it (you can find 3D-printed<\/strong> replacements online).<\/p>\n

\"\"<\/p>\n

I moved on and applied lithium white grease wherever was needed<\/strong>:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Then, I put back all parts of the floppy disk drive, and manually tested the eject<\/strong> mechanism<\/strong>. It was much better<\/strong>:<\/p>\n

\nhttps:\/\/www.quantum-bits.org\/wp-content\/uploads\/2022\/06\/mac_dd.mp4<\/a><\/video><\/div>\n

The floppy disk drive is now cleaned<\/strong> and oiled<\/strong>. But the motorized eject mechanism not functional for now<\/strong>. And the whole drive might be faulty<\/strong> (remember the abnormal blinking<\/strong> cross<\/strong> during the boot process).<\/p>\n

The analog board<\/span><\/p>\n

Let’s move on to the analog<\/strong> board<\/strong>. The first thing was to thoroughly<\/strong> clean<\/strong> it<\/strong>, using IPA<\/strong>, WD-40<\/strong> (for the anode cap) and contact<\/strong> cleaner<\/strong>:<\/p>\n

\"\"<\/p>\n

It looked so much<\/strong> better<\/strong> !<\/p>\n

\"\"<\/p>\n

Let’s have a closer look. I inspected solder<\/strong> joints<\/strong>, especially the ones from heavy<\/strong> components<\/strong>, like the flyback transformer. Everything looked<\/strong> nice<\/strong>. Good<\/strong> !<\/p>\n

\"\"<\/p>\n

I inspected the electrolytic<\/strong> caps<\/strong>, looking for leaks or budges. Nothing<\/strong> wrong<\/strong>, even the RIFA<\/strong> caps<\/strong> were looking good (though I will most probably change them<\/strong>).<\/p>\n

\"\"<\/p>\n

Let’s have a look at the flyback<\/strong> transformer<\/strong>. I was concerned<\/strong> with it because I heard static noises<\/strong> when I first powered up the Mac. <\/p>\n

Around the “neck” of the flyback, there should have been be some kind of yellow protecting coating<\/strong> like this one:<\/p>\n

\"\"<\/p>\n

This coating protects from corona<\/strong> discharges<\/strong>. With time, the “yellow goo” tends to dry<\/strong> and turns<\/strong> brown<\/strong>. It was the case for my Mac. Actually it disintegrated<\/strong> into pieces as soon as I touched it:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

If this transformer actually discharges, it is dangerous<\/strong> and it will fail<\/strong>. Repairing a flyback transformer is not an easy task<\/strong>, so I may have to replace<\/strong> it (and it is not something that can be easily found). This is a new concern…<\/strong><\/p>\n

The last thing I did during this phase was to clean<\/strong> the battery compartment.<\/strong> There was a tiny bit of corrosion<\/strong> (the PRAM battery wasn’t removed). It was an easy task, using white<\/strong> vinegar<\/strong>:<\/p>\n

\"\"<\/p>\n

\"\"<\/p>\n

Let’s now have a more detailed look at the analog board. As the name says, this circuit board contains the majority on analog circuitry. This is the international<\/strong> revision<\/strong>, labelled 630-010B<\/strong> and set for 240V<\/strong> operations:<\/p>\n

\"\"<\/p>\n

Let’s detail the essential parts of the analog board:<\/p>\n

    \n
  1. PRAM Battery compartment<\/strong>: the Macintosh Plus uses 4.5V PX21 batteries to keep settings such as time and date. This battery is not needed to boot the Mac Plus.<\/li>\n
  2. Power switch<\/strong>: on\/off power switch.<\/li>\n
  3. Power: <\/strong>socket for AC Power plug.<\/li>\n
  4. Ground<\/strong>: connected to the metal chassis.<\/li>\n
  5. Fuse<\/strong>: 1.6 A fuse (a 2.4 A fuse is used for 120V operations)<\/li>\n
  6. RIFA capacitors (X and Y)<\/strong>: RIFA<\/a> (Radioindustrins Fabrik Aktiebolag) was a Swedish electronics manufacturer of resistors and capacitors. RIFA capacitors are found on many units from the late 80s and early 90s. Class-X and Class-Y capacitors are safety-certified and generally designed and used in AC line filtering in many electronic device applications. RIFA capacitors, unfortunately are known to crack from thermal stress and aging, resulting in bad magic smoke and other havoc.<\/li>\n
  7. Power Transformer<\/strong><\/li>\n
  8. Brightness knob<\/strong>: Controls the screen brightness.<\/li>\n
  9. Speaker<\/strong>: internal speaker.<\/li>\n
  10. Height knob<\/strong>: Controls the screen height. Accessible from the back of the board, through the plastic protective sheet.<\/li>\n
  11. Voltage knob<\/strong>: Controls the screen voltage. Accessible from the back of the board, through the plastic protective sheet.<\/li>\n
  12. Logic board connector<\/strong>: harness, connecting the analog board to the logic board.<\/li>\n
  13. CRT connector<\/strong>: connected to the CRT yoke coil, controlling the beam deflection.<\/li>\n
  14. Anode cap<\/strong>: anode suction cap, plugged into the CRT with two prongs.
    Note: not visible on this picture, under the anode cap, lies the screen width knob (accessible from the back of the board, through the plastic protective sheet).<\/li>\n
  15. Flyback transformer<\/strong>: a FlyBack Transformer (FBT), also called a Line OutPut Transformer (LOPT), is a special type of electrical transformer. It generates high voltage (over 10kV) for the CRT.<\/li>\n
  16. Luminosity cut-off knob<\/strong>: Controls the screen luminosity cut-off. Accessible from the back of the board, through the plastic protective sheet.<\/li>\n
  17. Focus knob<\/strong>: Controls the screen focus. Accessible from the back of the board, through the plastic protective sheet.<\/li>\n
  18. CRT Socket cable<\/strong>: connects the analog board to the CRT tube.<\/li>\n<\/ol>\n

    The logic board<\/span>
    <\/strong><\/p>\n

    Let’s have a look at the logic<\/strong> board<\/strong>. The first obvious observation is that it is filthy<\/strong>:<\/p>\n

    \"\"<\/p>\n

    Let’s clean<\/strong> the logical board, with soapy water<\/strong> and a toothbrush<\/strong> and cotton<\/strong> swabs<\/strong>:<\/p>\n

    \"\"<\/p>\n

    \"\"<\/p>\n

    \"\"<\/p>\n

    During this cleaning process, I carefully removed<\/strong> the four<\/strong> 256Kb DRAM<\/strong> SIMM<\/strong>‘s from their sockets. Be careful, these connectors tend to be very brittle<\/strong> as time goes.<\/p>\n

    \"\"<\/p>\n

    Once removed, I found what was probably part of the flyback coating (from the analog board), stuck between RAM connectors:<\/p>\n

    \"\"<\/p>\n

    I cleaned<\/strong> the board with IPA<\/strong> and cotton<\/strong> swabs<\/strong>:<\/p>\n

    \"\"<\/p>\n

    I did the same with the back<\/strong> of the PCB<\/strong>, and took time to inspect<\/strong> it for bad<\/strong> solder<\/strong> joints<\/strong>. Everything was fine<\/strong>. Good.<\/p>\n

    \"\"<\/p>\n

    I finished the cleaning process with contact<\/strong> cleaner<\/strong>:<\/p>\n

    \"\"<\/p>\n

    \"\"<\/p>\n

    I took time to clean the DRAM SIMMs and used dioxide<\/strong> on the contacts<\/strong>:<\/p>\n

    \"\"<\/p>\n

    Once cleaned, the SIMMs were put back into a nice and fresh smelling logic board:<\/p>\n

    \"\"<\/p>\n

    Let’s detail the essential parts of the logic board:<\/p>\n

    \"\"<\/p>\n

      \n
    1. Microprocessor<\/strong>: the Mac Plus is powered by a Motorola 68000 processor, clocked at 8 MHz. It is a 16\/32 bits CISC<\/a> microprocessor. The design implements a 32-bit instruction set, with 32-bit registers and a 16-bit internal data bus. The MC68000 was widely used in the 80’s computers, especially for personal computer with graphical user interface. Beside the Macintosh, it was used by the Amiga<\/a>, the Atari ST<\/a> or the X68000<\/a>. The Mega Drive<\/a> console was also powered by a MC68000.<\/li>\n
    2. Oscillator<\/strong>: a 15.6672 MHZ crystal oscillator, manufactured by Fox (now Abracon)<\/li>\n
    3. Programmable Array Logic (PAL)<\/strong>: the logic board is based on several Apple-designed PALs (BMU, CAS, TSG, TSM, LAG, ASG, …). For example, the LAG IC performs the majority of the video control functions.<\/li>\n
    4. Intregrated Woz Machine (IWM)<\/strong>: The Macintosh disk interface uses a design similar to that used on the Apple II and Apple III computers, employing the Apple custom IWM chip, designed by the Woz<\/a>. Together with the VIA, the IWM and the ASG (Analog Signal Generator) generate all the signals necessary to read, write, format, and eject the 3 1\/2-inch disks used by the Macintosh. It is manufactured by VLSI Technology<\/a>.<\/li>\n
    5. Harness connector<\/strong>: Harness connected to the logic board.<\/li>\n
    6. Programmer’s switch<\/strong>: this switch can be activated by pushing the buttons on the side of the case, that were removed before opening the Mac. It triggers a NMI (Non Maskable Interrupt) that will make the CPU execute the assigned function (usually for debugging purposes).<\/li>\n
    7. AppleTalk connector<\/strong>: mini DIN<\/a>-8 AppleTalk connector. AppleTalk is a suite of networking protocols (now discontinued) designed by Apple for their Macintosh computers. It includes features that allow LANs to be connected without setup or centralized router.<\/li>\n
    8. Printer connector<\/strong>: mini DIN<\/a>-8 connector for serial printer.<\/li>\n
    9. SCSI connector<\/strong>: SCSI<\/a> stands for Small Computer System Interface. It is a set of standards for physically connecting and transferring data between computers and peripheral devices such as hard disk drives or tape drives, and later on CD-ROM, Zip Drives, etc. The Macintosh Plus was one of the first personal computers implementing SCSI. Actually, the SCSI implementation of the Plus was engineered shortly before the initial SCSI specification was finalized. It is thus not 100% SCSI-compliant and is thus very sensitive. The Plus uses a DB-25<\/a> external connector.<\/li>\n
    10. External floppy disk drive connector<\/strong>: DB<\/a>-19 connector for an external floppy disk drive<\/li>\n
    11. Mouse connector<\/strong>: DB<\/a>-9 connector for the mouse.<\/li>\n
    12. Internal FDD connector<\/strong>: internal connector for the 590-0437 (yellow stripe) 800K floppy disk drive cable.<\/li>\n
    13. SCSI controller<\/strong>: The NCR 5380<\/a> is an early SCSI controller chip developed by NCR Microelectronics<\/a>. It was the first single-chip implementation of the SCSI-1 protocol. <\/li>\n
    14. Serial Communications Controller (SCC)<\/strong>: The serial ports are controlled by a Zilog<\/a> Z8530<\/a> Serial Communications Controller (SCC).<\/li>\n
    15. Versatile Interface Adapter (VIA)<\/strong>: 6522<\/a> Versatile Interface Adapter (VIA) for the mouse and keyboard (manufactured by Rockwell<\/a>).<\/li>\n
    16. ROM (LO)<\/strong>: The ROM is physically split into two chips on the motherboard, labelled “ROM-HI” and “ROM-LOW”, respectively. The data in ROM is split in half between these two chips. The “HI” chip holds the high-byte of each address in ROM, while the “LO” chip holds the low-byte. The “LO” ROM chip is labelled here “342-0341-C” (i.e. ROM 64kb*8, V3). It is manufactured by VLSI Technology<\/a>.<\/li>\n
    17. ROM (HI)<\/strong>: The “HI” ROM chip, labelled here “342-0342-B” (i.e. ROM 64kb*8, V3). It is manufactured by VLSI Technology<\/a>.<\/li>\n
    18. Keyboard connector<\/strong>: RJ-11<\/a> connector for the keyboard.<\/li>\n
    19. RAM<\/strong>: The Macintosh Plus RAM is provided in four 256K Single In-line Memory Modules (SIMMs). Each SIMM contains eight surface-mounted DRAM chips. Memory can be expanded to a total of 4MB. When 1 MB SIMMS are installed, the 256K resistor (R8) must be removed or clipped to enable recognition of the higher density SIMMs.<\/li>\n<\/ol>\n

      Retrobrighting:  utter failures, fair results and a some success<\/span><\/p>\n

      Let’s now take care of these yellowed<\/strong> plastics<\/strong>. Yellowing in ABS (Acrylonitrile Butadiene Styrene) plastic occurs when it is exposed to UV<\/strong> light<\/strong>, which causes photo-oxidation of polymers<\/strong> that breaks polymer chains and causes the plastic to yellow<\/strong> and become brittle<\/strong>. It is a complex process, connected to (or at least accelerated by) the presence of bromine<\/strong>, a fire<\/strong> retardant<\/strong>.<\/p>\n

      The de-yellowing process is often called retrobrighting<\/strong> (retr0brighting, or retrobriting). It usually consists of using hydrogen peroxide<\/a>, combined with UV light and heat and sometimes “active oxygen” laundry booster.<\/p>\n

      There are many techniques, more or less complicated, more or less time consuming, requiring more or less equipment. One very effective method is the following:<\/p>\n