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The Macintosh Classic II, also called the Performa 200, was released in 1991. With computers of this age, corrosion and time often take their toll. In this case, the ever-present leaking electros had caused some damage. However, Bruce Rayne managed to make this old “classic” run again. I was 10 or 11 years old when I received my first computer. It had an 8-bit, 3.5MHz CPU, 8KB of RAM and used cassette tapes for data storage. After a couple of years, it was replaced with a faster computer and ended up in the bin. What reason could I possibly have to keep it when my new computer was so much faster? Fast forward 35 years where CPU speeds are measured in gigahertz, RAM is measured in gigabytes and hard drives are measured in terabytes, you would think those old computers would be long gone and worthless. But there’s been an incredible nostalgic resurgence in the popularity of these old devices. I saw my exact model of computer sell on eBay for nearly $300 a couple of months ago. You might think that it’s only people my age and older that are collecting vintage computers, but you’d be wrong. I’ve met teenagers who are collecting 25-year-old computers, fascinated by the role these devices played in the evolution of the personal computer. The more memorable and rare computers can sometimes go for quite obscene amounts of money. Apple’s very first computer (the Apple I) is so rare, siliconchip.com.au every single one known to be in existence is recorded in a registry, along with its sale price. In October 2014, one of these old Apples sold for over US$900,000. Not bad for a computer that sold for $666.66 back in 1976. One of the main selling points of any vintage computer is whether it still functions, but many of the internal components have a limited lifespan, so the older the computer, the greater the chance it will have a fault. Among the most troublesome components are electrolytic capacitors. They tend to leak electrolyte onto the PCBs, corroding surrounding components. Even when a working computer has been tucked away in a dry cupboard for years, it’s not uncommon for it to fail when it’s finally pulled out and switched on. But even worse than a leaky capacitor is a leaky backup battery. These were used to store settings and power the clock when the computer was off and can spew out corrosive chemicals if left long enough, sometimes completely destroying the computer from the inside out. This has lead to a niche business of restoring old computers to extend their operational life. The commonly Australia’s electronics magazine used term “recapping” refers to the replacement of old capacitors with new ones. After recapping a few of my own computers, I have recently started offering these services to others. It’s not a very profitable business model but I do get a great deal of joy bringing these old computers back to life. I’m always on the lookout for potential bargains, so when I see a vintage computer for sale as “not working” or “untested” (which means the same thing), I like to keep a close eye on it. If the price is right, I snap it up. The Classic II My most recent purchase was an Apple Macintosh Classic II. For those not familiar with this model, it followed the release of the Macintosh Classic, which was sold in 1990 as a sort of modernised version of the original compact Macintosh. In one of many strange moves by Apple, the Macintosh Classic offered very few improvements over the Macintosh Plus, a model released four years earlier. Although it now had a built-in hard drive and a slightly redesigned case, it had the same four megabyte RAM capacity, the same Motorola 68000 September 2019  69 Above: a close-up of the damage caused by leaky capacitors. Right: this version of the Macintosh Classic II used a 3.6V ½-AA PRAM lithium battery for CMOS backups, which had luckily not leaked. CPU and the same nine-inch monochrome screen. The one thing it had going for it was its low price tag, which made it very popular with schools and home users. As a result, over 1.2 million units were sold, and there are still quite a few Macintosh Classics floating around these days. A year later, Apple released the more powerful Macintosh Classic II, which looked almost identical to the Macintosh Classic but it was more closely based on the Macintosh SE/30, a model released in 1989. The Classic II had a Motorola 68030 CPU running at 16MHz and the RAM was expandable to 10MB. It had one empty slot for a ROM/FPU expansion card, but in a strange twist, Apple never released one! The Classic II was also a winner with the education and home user market, so they are also fairly easy to come by, though finding one that still works can be a challenge. Regardless of how well a computer like this has been treated or stored, chances are it won’t function today without a few repairs. The Classic II motherboard has between 13 and 16 SMD aluminium electrolytic capacitors (depending on the model revision) as well as a ½-AA size 3.6V lithium backup battery. All early compact Macs were held together with Torx screws, and not many people had matching screwdrivers. As a result, very few owners ever opened them up to replace the battery, so they’ve been left there to leak and corrode. The Classic II is comprised of three main internal parts: the cathode ray tube, the power supply board and the 70 Silicon Chip motherboard (referred to by Apple as the analog and logic board respectively). There is also a cooling fan, a 40MB SCSI hard drive and a 1.4MB floppy drive crammed into the case, plus a speaker mounted in the corner. The power supply board provides +5V, +12V and -12V DC outputs and also hosts the controller for the CRT display. Starting the repair I whipped out my trusty Torx driver and removed the four screws holding the back cover in place. Compact Macintosh cases are sometimes a little hard to open and require some gentle persuasion, but this cover came off with little effort. The corrosion from a leaky battery often spreads to the metal chassis in these Macs, but thankfully the chassis of this one looked clean. The next step was to inspect the motherboard, which sits on metal rails, so I unplugged the floppy cable, the hard drive cable and the power connector and that allowed the motherboard to slide right out. To my relief, I saw a completely intact backup battery. No leakage, no visible “battery cancer”. The whole board looked pretty good to the naked eye. It was the original revision of the motherboard, with 13 SMD electrolytic capacitors (eight 10µF 16V, three 47µF 16V and two 1µF 50V), plus a little blue jumper wire snaking its way across the board. This wire might look like a user modification, but it actually came like this from the factory. Later revisions of this model didn’t have the wire, so Apple obviously resolved this design flaw. Australia’s electronics magazine Each of the capacitors needed to be removed and the pads cleaned. Many of the ICs also needed to have their pads cleaned. siliconchip.com.au Some traces had also been damaged by corrosion from the electrolyte. The example shown above was fixed by soldering copper wire from the nearby via to the SMD IC shown below. This was then cleaned with an ultrasonic cleaner. siliconchip.com.au I put the board under the microscope and could immediately see the results of electrolyte leakage from the capacitors. All of the surrounding components had a caked-on yellow crust, something I have seen many times before. The whole board would need a thorough clean. The first thing to do was to get rid of the old capacitors. I use a hot air rework station. Some people like to use solder tweezers, and I’ve even seen someone who likes to cut the tops of the capacitors off, just leaving the pins, then remove them carefully with a regular soldering iron, but I prefer hot air. I use little flat pieces of steel as shields, positioned carefully around the capacitors, to minimise the amount of hot air spilling onto other components. It’s 27 years since this computer was assembled, so I don’t want to push my luck by blasting too much of it with too much hot air. Once the capacitors were off, it revealed large amounts of electrolyte residue around the old pads, but it looked far worse than it was. I started to clean this up by adding a liberal amount of a good quality gel flux, then I added some new solder to the dirty pads and gently moved the flat part of my bevelled soldering iron tip around the pad to melt any old, crusty solder. This is definitely not a job for a conical tip; I prefer fine bevel or small chisel tip. Next, I grabbed some solder wick and gently soaked up all of the solder from the pads. Ever so gently, I rubbed the pads with solder wick to clean off any remaining residue. Finally, I used a cotton bud soaked in isopropyl alcohol to clean off the excess flux, which revealed a sparkling clean pad, ready for the replacement capacitor. There were some ugly looking solder joints on a nearby transistor, so I Australia’s electronics magazine took the opportunity to remove it as well, then cleaned the pads before reattaching it using fresh solder. After removing one of the capacitors, I could see a break in one of the nearby traces. The localised corrosion was so severe, it had eaten right through the solder mask and trace, so that would need to be repaired. It took me a while to remove all 13 capacitors and clean the board up. I was then ready to fit the replacements. For many restoration purists, replacing the electrolytic capacitors with tantalums may seem like vandalism, but I have more interest in preventing future capacitor leakage than I do in preserving the exact look of the original motherboard. I also like to remove the original ½-AA battery holder and replace it with a 20mm button cell holder, as 3V CR2032 batteries are much easier to source, and the computers don’t seem to mind the 0.6V difference between the two battery types. With all thirteen capacitors replaced, I turned my attention to the broken trace. I followed it up to a nearby via, then using a curved surgical scalpel, I gently scraped away the solder mask, revealing fresh copper. I then applied some solder to the copper and soldered some 0.2mm diameter enamelled copper wire to the exposed copper. I then ran the wire around to the other end of the broken trace, which was the pin of a surface mounted plastic-leaded chip carrier (PLCC) IC. I scraped away at the trace coming out from the destination pad (to increase the solder area for the other end of the wire) and trimmed the repair wire to a more suitable length. After repeating the same soldering process to secure the other end of the September 2019  71 wire, I used my multimeter to confirm that the repair had restored continuity. The only thing left was to give the board a good clean. I’ve heard that some people like to clean these old boards with soap and a toothbrush, while others like to resort to the household dishwasher but I wouldn’t recommend either approach. I use an ultrasonic cleaner filled with a diluted detergent designed specifically for PCB cleaning. I dropped the board into the ultrasonic cleaner then gave it about 15 minutes on each side. Ultrasonic cleaners do a great job of cleaning gunk out of tiny crevices, while still being quite gentle. Once the cleaning was complete, I dropped the board into a bath of isopropyl alcohol. This helps to wash away any residual water and detergent, and the low evaporation temperature of the alcohol also speeds up the drying process. I use a small toaster oven set to a very low temperature (around 60-70°C) for drying cleaned boards, leaving the boards in the oven for about 60-90 minutes. Once out of the oven, I gave it a quick inspection while waiting for it to cool. Almost all of the residual electrolyte gunk was now gone, and the trace repair had held together well. Even though the repair looked solid, I still applied several coats of UV-curing solder mask for extra protection. I usually use a UV globe to cure the mask, but it was a sunny day, so I left it in the sun for a few minutes instead. The repaired and cleaned motherboard shown above. Note the CMOS battery and holder were replaced with a much more common CR2032. The power supply board looked fine at a glance, but had large amounts of electrolytic capacitor leakage on the underside (shown below). Testing I put the computer back together, plugged in the mains power cord, flicked the power switch and got nothing, not even a crackle or a pop. It was completely dead. I grabbed my multimeter to see if I was getting any power at all. The external floppy drive connector can be used to check the output voltage, and I read just 2V on the 5V pin, so the power supply board would need some attention. After discharging the EHT, I removed the power supply board and gave it a quick once-over to see if there were any obvious problems. I didn’t find any burn marks, but what I did find was a huge amount of electrolyte leakage near a small cluster of eight electrolytic capacitors. They all needed to be replaced. This is a known failure point for these 72 Silicon Chip Australia’s electronics magazine siliconchip.com.au boards, so I keep a good supply of replacements. I de-soldered the joints for all eight capacitors and pulled them off the board. This revealed the full extent of the leakage, with dirty brown rings of liquid under each capacitor. Cleaning the power supply board is a little trickier than cleaning the motherboard, as it has a small speaker riveted to the surface. Submerging a speaker in an ultrasonic cleaner wouldn’t be the smartest move, so I used a little isopropyl alcohol and a toothbrush to get the worst of the gunk off the board. Once cleaned, I then soldered in the replacement capacitors. Before reassembling the computer for another test, I took a few moments to inspect the solder joints. Some of the components on the power supply board are relatively large and bulky, so the weight can sometimes cause cracks in the joints over time. I found a few ugly looking joints, so I removed the old solder and replaced it with new stuff, just to be thorough. With fingers and toes crossed, I put the Macintosh back together and powered it up. I got the familiar “ding” sound of the Macintosh startup chime. A couple of seconds later I heard more “dings”, meaning I wasn’t quite finished yet. The computer was starting but kept restarting itself in an endless loop. Chances were this was being caused by the voltage being a bit low and I could probably fix this with a minor adjustment. My multimeter showed about 4.5V on the 5V power rail. Thankfully, the power supply board is equipped with a small potentiometer for minor voltage adjustments, so I gave it a twiddle until the voltage read exactly 5.0V. The reboot loop stopped and the Macintosh started booting into an operating system from the 27-year-old, 40-megabyte internal hard drive. A quick glance at the original owner’s files revealed that this computer hadn’t been used in nearly 20 years. As I intended to sell this old Mac, I went ahead with a few other housekeeping tasks, such as replacing one of the cogs in the floppy drive eject mechanism, as this is a well-known weak point. Don’t ask me why, but of the four cogs in the mechanism, one of them changes to the consistency of an aged cheese when it gets old, while the others are unaffected. Even though this one had not yet failed, its disintegration was inevitable, so I saved the future owner from any potential headaches. I also gave the floppy drive heads a good clean, then erased the internal hard The black potentiometer (PP1) on the power supply board provides minor voltage adjustments, and was needed to adjust the 5V rail. The floppy drive eject mechanism in the old Macintosh Classic IIs had a habit of deteriorating, as seen by the yellowed cog at far right. siliconchip.com.au Australia’s electronics magazine drive and installed a “fresh” operating system. Even though a quick block test of the hard drive came up clean, it’s a miracle that this drive still works, and it could fail any day. Thankfully there are modern replacements available, such as the SCSI2SD adapter that allows the old SCSI hard drive to be replaced with a modern micro SD card. Now that the Macintosh Classic II works, what can you do with it? The answer is quite simple: you can do anything you could do with it in 1991. There are a large number of online resources with vintage software that can be run on these old computers: word processors, spreadsheets, graphics, games, music etc. Thousands of old applications that will run beautifully on a computer of this vintage. And that’s precisely what the collectors want to do. They want to relive their past by playing old games from their youth, writing a letter on Microsoft Word version 5.0, or composing a musical masterpiece for playback on the tinny, 55mm speaker. It’s all a bit silly, but it’s also a lot of fun! Extra Links Schematic diagrams (the SE/30 is close in specifications to the Classic II) – siliconchip.com.au/link/aaqd Developer notes – siliconchip.com. au/link/aaqe Service guide – siliconchip.com. au/link/aaqf SC September 2019  73