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SERVICEMAN'S LOG Old-fashioned appliance repairs still worthwhile Dave Thompson* As mentioned before in this column, I’ve recently started advertising for different types of repair work. As normal service work continues its inevitable decline, other opportunities come knocking. I don’t mean opportunities like some talent scout discovering me and offering me a movie deal (though of course this might still happen). I’m talking about opportunities that come about because I’ve been putting myself out there; shaking the trees to see what falls out, as it were. There are many home-based businesses in Christchurch these days, because of the post-quake lack of suitable buildings and profiteering on what little usable space is still available. 58 Silicon Chip Hundreds of businesses down-sized into converted garages and porta-cabins, turning them into design studios, beauty salons, paint booths or in my case, a computer repair workshop. But the council, who claimed to be 110% behind the rebuild, threw up so many unnecessary roadblocks to small business owners that many simply didn’t bother reopening. For example, I plopped a 10m2 porta-cabin on our front lawn from which to temporarily operate. I was advised Celebrating 30 Years by the people selling and renting portable structures that this was the largest building I could install without needing planning consent. However, in my naivety, I neglected to put it further than four meters from the street boundary of my property. It transpired that in order to operate a business in a portable structure within this distance from the street, I had to jump through all manner of bureaucratic hoops. First, I had to get the permission of all the neighbours in siliconchip.com.au my street and the surrounding streets. I also had to declare the date by which I would vacate the temporary premises. Obviously, I’d need to get out my crystal ball because at the time, nobody had any idea of how long it would take to get back to normal. In the end, I had to agree to move out from my new workshop after just 12 months, making the cost and worth of doing all this a lot less appealing than it had seemed initially. The council apparently weren’t all black-hearted though; they did make some concessions to allow us to operate from our temporary workshops. For example, we were allowed five times the size of the normal regulation signage for businesses in residential areas. At least we could advertise our presence to potential customers! But then I learned that the original maximum sign size was a whopping 200 x 60mm and the council, in its infinite generosity, would now allow us up to 200 x 300mm. That’s less than the size of an A4 sheet of paper. Overwhelmed with their generosity and spirit, I indeed did put up an A4sized poster. I asked the humourless inspector who came to check (Oh yes, they checked) if I could put the 4 x 3 metre sign from my original workshop on my garage door, which was down the drive a fair way from the street or on the roof of the cabin instead and was told "no!". If that sign was visible from anywhere (including from the air!) they would prosecute; unbelievable, but true. Luckily though, there is a relatively new website over here designed to bring communities closer together. This helps neighbours who may not know each other; to introduce themselves and their families and assist in keeping everyone in touch with what’s happening around them. The ultimate goal is to try and get back some of that community feel we had in the “old days”, where everybody knew and looked out for each other. But it has also turned out to be a great place to let neighbours know about the numerous small businesses lurking within their midst. This was a bit of a blessing, so I put my details out there at the earliest opportunity. And as we have a school entrance across the road, having even minimal external signage might catch the attention of school-run parents. siliconchip.com.au As a result, I’ve had a few computer repair jobs but the biggest response was from an article I posted responding to someone asking about appliance repairs. I didn’t say I fixed appliances but instead posted a response agreeing with someone who was lamenting throwing out an appliance because repair companies aren’t particularly interested in fixing them any more, preferring instead to sell a new unit. I offered to take a look and in the meantime, the original post gained some traction, with many posts from people dissatisfied with other repair guys. At that point, I flagged my interest in having a look at some of these broken appliances with an eye to repairing them. I suggested that I would assess first before advising the customer about the potential costs involved and then they could decide whether to proceed. Since then I’ve had an array of blenders, stereos, a turntable, desktop ovens, coffee machines and a couple of cordless drills to look at; and I couldn’t be happier! Variety is the spice of life, or so they say. I certainly enjoy the challenge that some of these devices bring to the workshop. Most can be fixed, relatively inexpensively, with many not even requiring spare parts; just a little creative fettling to get them back to serviceability. Diagnosing a sick blender For example, one neighbour dropped off an older-style blender for me to have a look at. She complained that it only worked intermittently, though when it did work, it worked very well. Celebrating 30 Years Items Covered This Month • • Blender repair Fixing a MacBook Air laptop *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz She’d taken it to another outfit and they’d told her it was past it and she needed a new one, then charged her $45 for the privilege. She suspected those guys hadn’t even looked at it and felt certain the blender just had a loose connection or faulty switch. It was a good unit; a quality brand with a very heavy, polished cast-aluminium base and a thick Arcoroc jug. It was clearly built to last and to be repaired, and was still in good condition if a little dirty. When she dropped it off, she mentioned that she thought the switch might be the problem as it sometimes didn’t feel solid in operation. The first thing I did was plug it in and switch it on. Nothing happened, though of course, it wouldn’t, as I didn’t have the jug attached. Most higher-end blenders have a safety-switch arrangement that disables the motor power if there is no attachment present or it is not fully twisted home. This prevents things potentially getting messy. On the top of the heavy base, right next to the cast fittings for the jug to screw into is a small hole, with a small plastic pin protruding from it. October 2017  59 When I manually held this pin down, I could feel and hear a microswitch inside the blender actuating. With this switch actuated and the blender switched on, the motor kicked into life. I tried it a few more times and every time the pin was pushed in, the motor fired up. I toggled the main switch back and forth but it seemed solid. I suspected that this pin was the issue; it had worn down over the years so that it was now barely flush with the raised metal housing. It must be very close because with the jug in, sometimes it worked and sometimes it didn’t, leading the owner to think (quite sensibly) that the switch was failing. What amazed me was that those other repair guys hadn’t spotted this most obvious of problems. Or perhaps they did and just couldn’t be bothered doing the work; I don’t know. To my mind, this would be relatively easy to repair. I contacted and quoted the customer and when she happily agreed, I set about fixing it. Chalk one up for Dave I considered extending the pin or grinding the metal shroud down around the pin, exposing more of it, but that seemed a bit barbaric and I wanted to see how it worked inside first. The only way in was through the bottom and of course it had some of those horrible Torx-style security screws holding the base on. These are the type with a small pip in the centre, making it impossible for a standard Torx driver to get purchase onto the screw head. They’d made it even harder by sinking the screws into the plastic bottom housing by about 40mm, with a relief diameter smaller than a standard bit-holding driver shaft. This meant that normal drivers and bits, like the one I use, had no chance of getting anywhere near the screws. However, I tried the bit by itself and it did fit down there, so I took it out and stuck it in my metal-working vise. I then fitted my Dremel with a 0.5mm cutting disc and cut a small channel in the bottom large enough for a small flat head screwdriver to fit into. After cleaning up the cut, I returned the bit to the first hole and after a bit of positioning, simply used my screwdriver to undo it. I refuse to be beaten by these manufacturers with their stupid security fasteners. There is always a way around them, so why bother with them? Once the bottom was off, the motor and switching arrangements were revealed. I checked the brushes and they appeared to be about half worn, with plenty of life left. The motor was certainly a chunky unit, leaving little room for anything else inside the case. I shone a light down the side and could see the plastic safety switch. It looked like a simple plastic piece sandwiched between the microswitch, which was mounted on the motor’s field windings cage, and the inside top of the case. If the pin was pushed down from the top, that pressure transferred directly to the toggle of the microswitch; simple yet very effective. To get it out, I’d have to move the motor and this involved removing four screws, two of which were partially obscured by wiring and the main switch body. At least these screws had standard Phillips-style heads on them, so I could use a long, thin driver to angle around the switch housings and field windings to get to the screws and get them out. I briefly considered removing the hard-rubber drive arbor but decided against it. It appeared to be moulded on and I was afraid if I did get it off, I might not be able to get it back on again (not for the first time). I did try unscrewing it with my hands, both ways, and had a go gently levering a couple of large-bladed screwdrivers underneath it but it didn’t give at all so I gave up. Knowing when to stop is part of the game. With the four screws out, I was able to jiggle the plastic switch toggle out. As I suspected, it was simply a bit of injection-moulded Nylon and the pin had worn down over time. There was Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column? If so, why not send those stories in to us? We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. 60 Silicon Chip Celebrating 30 Years no way to make it bigger; I considered swapping the pin for a screw, but that might end up chewing out the plastic bottom of the jug, so in the end I decided to build it up underneath. There was some play where it touched against the microswitch and building it up would cause the pin on the other side to poke through the case a bit more. I did this by first drilling out the raised plastic area that touched the switch, a 6mm-diameter circular moulding that protruded 3mm toward the switch toggle. Using a PCB drill, I drilled four holes into the round block. I then created a turret-shaped mould with heavy masking tape around the block and mixed up some 24-hour epoxy to fill it with. I had to heat the epoxy up a bit with my heat gun as it was too cold for it to run very well. Once warm though, it was quite liquid, and using a cotton bud I dripped the epoxy slowly into the small mould. I was careful to avoid getting bubbles in it and manipulated it to ensure the holes were filled. The next day, I removed the tape and with needle files, shaped the area to match the rest. When I reassembled everything, the pin protruded about 1mm from the top; more than enough for the jug to actuate the switch. A good fix, and one less appliance needlessly thrown away. A win-win, as they say. Repairing a badly broken 13-inch MacBook Air B. R., of Seven Hills, NSW has taken to repairing Apple Mac laptops. These can be a challenge but he has some handy tips in this next story... Over the past few months I’ve been occupying my spare time repairing broken Apple Mac laptops. I’m not actually a computer repairer; I just buy broken Apple MacBooks at a discounted price on eBay, repair them and then re-sell them (or sometimes I just keep them for myself). I don’t do it to earn money, I just do it as a hobby so any money made is an added bonus. Here’s an account of my latest MacBook repair, as well as some of the important component-level repair information I have learned. Firstly, I’m very selective about what I will repair and I prefer laptops rather than desktop computers. Most desktop computers in need of repair get sold without a keyboard and mouse. So if I am planning to re-sell them as a comsiliconchip.com.au plete package, I have to factor in the cost of a new keyboard and mouse. And if I have a few repairs on the go at any given time, the laptops are far easier to store. Another important factor is the resale price. Laptops seem to hold their second-hand value much better than their desktop counterparts, so that gives me a better chance of selling for a profit. I stick to Apple Mac laptops because they usually sell for more than an equivalent Windows laptop and there seems to be a good supply of second-hand and after-market replacement parts. And finally, laptops seem to get damaged by liquid quite often, which is usually easy to repair. Most of the broken laptops I come across fall into three categories: liquid damage, cracked screens and failed graphics chips. I usually steer clear of the last two and try to buy the liquid-damaged laptops as often as possible. It really is quite extraordinary how many laptops end up with some sort of liquid being spilled on them. I certainly can’t judge, as I have given my keyboard a drink from time to time. Not all spills mean the instant end of a laptop, but corrosion can build up on the liquid-affected parts, and one day the laptop might just stop working. Computer manufacturers typically won’t do any component-level repairs. If you have a corroded component on the computer’s motherboard, they will replace the whole motherboard. Depending on the age of the computer, that can easily cost more than the device is worth and that’s why they regularly end up for sale on eBay at cheap prices. Some repairs aren’t as easy as expected I recently purchased a 13-inch MacBook Air on eBay, with the symptoms described as “Laptop does turn on however runs very slowly”. I know from experience that with a MacBook Air, this is usually caused by a faulty sensor and I know that faulty sensors are often caused by corrosion from liquid damage. And corrosion is usually easy to see on the motherboard. The laptop was going for a pretty low price and the repair would (hopefully) be fairly inexpensive, so this one seemed like a good candidate. I made the purchase and waited for it to arrive. A couple of days later, siliconchip.com.au This peculiar fault is caused by the cracks in the screen of the MacBook Air laptop. This was the initial bootup screen, showing different language options. my friendly neighbourhood delivery man arrived at my front door with the “new” laptop. The first step was to switch it on, and to my joy, it made all the right noises and booted into a new operating system (albeit painfully slowly). But that joy suddenly turned to despair when I noticed a 20cm-long crack, right down the middle of the LCD screen. As I mentioned before, I always try and avoid cracked screens because they can’t be repaired (only replaced) and the parts are very expensive. Unless you can pick up the computer for an absolute bargain (or you already have a spare screen in your possession), they’re just not worth buying. The cracked screen I quickly assessed the package and found out what had happened. The seller had placed the laptop and the charger into a very flimsy padded bag. At some stage while in transit, someone had parked a heavy weight on it and the charger was pressed into the lid of the laptop hard enough to crack the screen on the inside. What was originally an easy fix had now become a monCelebrating 30 Years umental pain in the backside. I contacted the seller, who was very understanding and very apologetic. I took the package to my local Post Shop and asked what could be done. They kept it for a few days for assessment, but then decided that the level of padding was insufficient, and as such they would provide no compensation. At this point, I told the seller and they refunded my money in full. I then told them that I would still be interested in buying the laptop but only if they dropped the price significantly. They agreed to the new price and I kept the laptop. I guess it all worked out reasonably well in the end; the seller still got some money for it and I still had a chance of repairing the computer. I just had to find a replacement screen at a reasonable price. October 2017  61 I decided to fix the “brains” of the computer before I tracked down a replacement screen, so I headed to my workshop and began disassembling it. For any computer I dismantle, I always use the guides on the iFixit website (www.ifixit.com). You just type in the model of the computer and if it’s on file, a whole list of disassembly procedures are displayed, along with pretty pictures of all of the different screw types, sizes and the correct order for their removal. It sure saves me a lot of time. Gone are the days of a few little Phillips head screws, with most modern laptops now being held together by a whole range of screw types, designed to stop us from unscrewing them. There are Phillips screws, Torx & Torx plus, hex, pentalobe, tri-lobe and split screws. Just when you think you have tools for all of them, you open up a computer and find a screw you’ve never seen before. But I’m not easily discouraged, even though manufacturers seem to go out of their way to make repairs difficult. Some (famously including Apple) will refuse to work on a computer that has been repaired by someone else, so be prepared for failure if you’re planning to try this for yourself. And never dismantle a computer that is under manufacturer’s warranty as you will almost certainly void it. Most of the computers I work on are three to five years old, which is enough time for any common faults to be well-documented. For example, I mentioned before that some of the MacBooks suffer from failed graphics chips. These chips are usually made by ATI or NVIDIA and are designed to be extremely powerful but seemingly at the expense of reliability. Ball Grid Array (BGA) chips The graphics chips run at constant- The BGA package underside, showing the solder balls. 62 Silicon Chip ly high temperatures and some of them fail after only a few years (and sometimes quicker). These are often difficult or even impossible to repair. Graphics chips are usually in Ball Grid Array (BGA) packages, which means they have a grid of tiny little solder balls on the underside of the chip housing. These line up with an array of pads on the motherboard. Heat is applied during assembly and the solder balls melt, attaching the chip to the board. For a large chip (like a graphics chip) which could easily have 500 or more contact points, replacing it is no easy task without specialised equipment. And that’s assuming you can find a suitable replacement. You may be forced to get one from another computer, which might fail in a week’s time! And don’t be tempted by all of the videos on YouTube of people “repairing” faulty graphics chips by using a heat gun on the chip or by putting the motherboard into the oven for a brief period. These videos will usually feature a dead computer, which is then dismantled. Heat is applied to the graphics chip, then it is allowed to cool and Voila! It works again! It sounds so easy. The reasoning provided for this procedure is that the solder balls under the chip have come away from the board and the heat is reflowing the solder, restoring contact. But in most situations, this is just not the case. Modern computers use lead-free solder, which has a melting point of about 190°C and in most of these demonstrations, these chips aren’t getting hot enough for the solder to melt. So why do they miraculously start working again? The answer is from inside the chip housing, not under it. The heat temporarily restores the tiny little contacts between the chip inside and the housing around it but it’s often just a short-term fix. So when I see a computer for sale with a dead graphics chip, I leave it for someone else. An important part of any fault diagnosis is having access to schematic diagrams and board-view files of the computer you’re working on. While manufacturers normally hold these close to their chest, they do often get into circulation and a quick search on the internet may be fruitful. Downloading these documents is an infringement of all sorts of manufacturer rules but it seems to be a fairly common practice and not policed. But you do so at your own risk. Board-view files are a CAD-style drawing of the motherboard, including every single component in its place, The MacBook's motherboard before repair. You might be able to spot where the corrosion is on the board, from this photo. Celebrating 30 Years siliconchip.com.au Directly above is the board-view file for the motherboard, and to its right is a close-up of the selected area which shows the effects of the corrosion. Board-view files are like CAD drawings, but also include information on the placement of every component and how each is connected to the other. along with how each component is linked to every other component. They need to be viewed with a specific application, and there is a fantastic (and free) one called OpenBoardView, which is available for Windows, Mac and Linux. Used in conjunction with a schematic diagram and multimeter, there’s very little that can’t be diagnosed, as long as you have a solid knowledge of electronics. Initial diagnosis So after opening my broken MacBook Air, I pulled out the motherboard for a closer inspection. I very methodically went over all of the components with a magnifying glass until I found… yuk! A nice little nest of components, all showing corrosion from liquid damage. So the next step was to refer to my trusty board-view to find out what these parts do and if they were likely to be the cause of my problem. Sure enough, they were very likely candidates. They all reside right next to the System Management Controller (SMC) which is responsible for controlling many of the physical parts of the machine, such as indicator lights, fans and (drum roll)… sensors – the most likely cause of my slow-running Mac. Some of the little resistors and capacitors were so badly corroded, they had actually cracked in half, so they needed to be replaced. The next step was to remove and replace all of these damaged components. I didn’t bother testing them all to see which ones were faulty, I just decided to replace all of them in the area of corrosion as it would be quicker. I could have ordered these components from a supplier but generating a list would have been tedious and many of them are not available in small quantities. The logical solution is to locate a “donor board”. These are motherboards from exactly the same computer model, made available cheaply on eBay, with many of the components still in place. They have had all of the important chips removed (like the CPU, RAM The $24 donor board, as delivered straight from China. This board had most critical components stripped from their sockets, such as the CPU, GPU and RAM. siliconchip.com.au Celebrating 30 Years and graphic chips) and have a couple of small holes drilled through the board (so that you’ll never be able to repair them). There’s no guarantee that all of the parts on these boards are OK, but since they are quite cheap, it makes sense to buy a couple, in case one has damage in the same place as yours. My computer has an 820-3023 motherboard and I was able to buy a suitable donor board for just under $24, including delivery from China. So then it was just a matter of waiting for the donor board to arrive. Just under two weeks later, I had my donor board. Thankfully, the parts I needed were all clean and intact, so I was ready to start the transplant. Some of these components are small, and I do mean small! Seven of the resistors I replaced were 0.6mm x 0.3mm. To provide some scale, an adult flea is around 2.5mm in length, so you really want to avoid sneezing while you’re doing this work! The donor board Before I go into details of the repair, here are some of the absolute essential tools needed to do these sorts of component-level repairs. The first is a good quality soldering iron. It needs to get hot enough to melt lead-free solder, and will need a very fine tip. I use a Hakko FX-951, but these are a bit pricey and a cheaper option would probably do the job just as well. Just make sure you don’t use one of those simple all-in-one irons with a great big fat tip for soldering household power cables. Use a good qualOctober 2017  63 The components from the donor board, after having been transferred onto the original. One of the traces had corroded enough to split, so it had to be bridged using 0.1mm diameter wire. After cleaning and drying the board, this spot was covered with a small amount of silicone coating, as shown on the photo to the right. ity soldering station with a reasonably high output (mine is 70W). The next essential item is a hot-air rework station. These are like a hotair gun but with an adjustable temperature and airflow, and a selection of nozzles. Their main advantage is that you can heat a whole component, rather than just a single contact point and you can use them to solder or desolder components with hidden pads on the underside. If you’re trying to remove an IC with 30 or more pins, it’s impossible to melt the solder all at once with a single soldering iron. A basic hot air rework station can be bought for well under $100. You also need a good fume extractor. I choose to use leaded solder as I like working with the lower melting point but both lead and flux are toxic, so good ventilation is essential. Another important item is solder wick. This is a finely-braided spool of copper wire that will draw in solder when heat is applied. It’s usually impregnated with flux and since you only use a small amount at a time, it’s quite cheap. This helps you to remove solder from a PCB. I always clean the old solder off and apply new solder before putting new components in place. You’ll also need a good quality solder. I use a 0.35mm diameter 37% lead, 63% tin solder, which is specifically designed for surface mount work on PCBs. And lastly (for now) you need a good quality no-clean flux. Just because your solder has flux in it already doesn’t mean you should skimp on the flux. Flux helps the solder flow 64 Silicon Chip so a liberal amount of good quality flux is the difference between doing a good repair and ending up with a globby mess. If in doubt, add more flux! I use Interflux gel, which is available in 10cc syringes from Mektronics Australia. You’ll also need a few smaller tools like tweezers and a good magnifying glass (or microscope) and plenty of light shining on your work area. Doing the repairs So the first step in my component transplant was to remove the old components from the corroded area of the board, which I did with my hot-air station and a fine pair of tweezers. I didn’t need to keep any records of what I removed from where because I had my donor board with all of the components in their correct position to use as a reference. Next, I used some solder wick and applied heat from my soldering iron to clean off all of the old solder. When using wick, make sure that you lift the iron and wick away from the board at the same time, while the solder is still liquid. Don’t lift the iron first or the wick will stick to the pads and then you’ll rip them off when you lift it. It’s important to be very gentle at this stage, because the pads are quite fragile. If the wick gets stuck, you’ll need to apply more heat with your iron until it moves freely. With the pads free of solder, I melted fresh solder onto each pad, ready for the new component to go in place. Next, I laid the two boards side-by-side and transferred the components one at a time, so that I didn’t get them mixed up. I used my hot air station to heat Celebrating 30 Years the donor board, lift off a component with the tweezers, then place it in position on the original board. I then gently adjusted the component’s new position, relying on flux paste to hold it steady before applying heat with the hot air station to melt the solder. Surface tension then pulls the component into place. This takes a lot of practice but if you do it correctly, you don’t even need to touch the component when the solder is melting. As long as it’s close to where it’s supposed to be, it’ll just naturally settle into the correct position, pulled by the melting solder and flux. This process would not be possible without adding a good quality flux. All up, this process took me about half an hour, replacing eleven separate components: seven resistors, three capacitors and a small transistor. I put the computer back together to try it out and was extremely pleased when it started up, but disappointed to find that it was still running very slowly. So after all that work, I still hadn’t fixed it. So I pulled it all apart (again) and tried a few more tests. I was confident that the problem was still located in that area of corrosion, so I started looking at the traces, rather than the components. I grabbed my multimeter, put it into resistance mode and carried out some continuity tests in that area. I found one spot where the signal clearly wasn’t getting where it needed to go. There was a point on the board that had been corroded so badly the trace had split apart. So now I had to find a way to create a bridge across this ugly mess. Using a very sharp blade and a steady hand, I gently scraped off a bit siliconchip.com.au Left: the ultrasonic cleaner used on the motherboard, after which it was placed in 100% alcohol and dried in an oven. Right: reassembling the MacBook with the now repaired motherboard. of the protective solder mask layer on top of the trace, exposing the copper beneath. I was then able to solder some 0.1mm diameter wire to bridge from one side of a resistor to the exposed copper, bypassing the corrosion. This was incredibly fiddly, and didn’t look too good, but it did the job, restoring continuity. So now with my fingers and toes firmly crossed, I put it back together for another test. Hooray! It was working at its normal speed; I had managed to fix it. Even though I use a no-clean flux, I still like to get the board nice and clean before reassembly, so I dropped it into my ultrasonic cleaner. I use an inexpensive ultrasonic cleaner with a cleaning solution specifically made for PCBs. eBay is probably the best place to look for an ultrasonic cleaner but just make sure you get one that’s big enough for the stuff you need to clean and has a built-in heater. Definitely don’t buy one of those really cheap jewellery cleaners. The cleaning solution I use is called “Electro” and can be purchased as a concentrate from Kleentek. It’s very counter-intuitive placing electronics into a liquid, but it’s quite safe as long as the board is well dried before applying any power. After cleaning, I placed the board in a small bath of 100% isopropyl alcohol (which helps to displace any water). I then heated the board in my kitchen oven for about 20 minutes, on a very low temperature (about 80°C) to dry it out. I could have just let the board dry by itself, but the oven speeds up the process. This may sound scary but it’s a process that I’ve done many times and it has never caused any damage. siliconchip.com.au With the board repaired, clean and dry, the last step was to put a small drop of silicone coating on the area I repaired to protect it. I then put everything back together. The most frustrating part of getting to this stage in the repair was knowing that if the screen hadn’t been cracked in transit, I’d be done now! The final steps I began searching for a replacement screen assembly. I found plenty on eBay but they were going for about $500 each. That was going to put a nasty dent in my profit margin! Sometimes it’s just a matter of looking at the right time, so I kept checking every few days to see if a more reasonably-priced display became available. After a week or two, I saw a second-hand display appear on eBay. The description said “screen working perfectly... no dents... 30 day war- ranty” and it was selling for a lot less than any I had seen so far, so I grabbed it. A couple of days later, the new screen arrived, so I looked up the replacement procedure on iFixit and did the swap. The new screen was in really good condition so after a quick clean, the whole thing came up looking a million bucks. It ended up costing me a bit more than I was expecting, but I still managed to make a small profit after selling it and I had fun too! Conclusion I learned many of these repair procedures by watching YouTube videos posted by New York laptop repairman Louis Rossmann. His language is a bit colourful at times, and he likes to rant, but he has literally hundreds of videos on repairing Mac laptops. It’s an invaluable resource for anyone thinking about doing their own repairs. SC Almost as good as new; the laptop with a repaired motherboard and a replacement screen. Celebrating 30 Years October 2017  65