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SERVICEMAN’S LOG Can’t stop servicing, even on holiday! Dave Thompson Five years have passed since I have had a proper holiday (not just the odd day off), where I get to laze around and do nothing, or at least whatever I want. All without the phone ringing, email notifications going off, or people turning up at the workshop, expecting me to fix something while they wait. Sometimes, it’s hard to stay above it all, a feeling I’m sure most of you are familiar with! Many people will likely synchronise whatever holidays they get each year with kids’ school holidays or their own time off work. As a sole trader with no school holidays to worry about, I often don’t get to have the usual days off. There is always something to do, whether it is researching or making components from scratch for weird jobs, or trying to track down spares for my work tools. Then there’s all the usual household maintenance. I suppose I could pay someone to do that, but it seems a bit silly to shell out for someone to come around and mow lawns, or clear gutters while I am still relatively capable of doing it. So, a holiday then, a real one, which involves travelling to Europe to visit family. We were due to go a few years ago, but sadly, world events got in the way. That made it difficult and expensive to go anywhere, so we knuckled down like everyone else and just got through it as best we could. Finally, things have returned (somewhat) to normal, so we took the opportunity to take some time off. My wife is lucky in that she permanently works from home, and part of the deal was that she would do a few days of remote work each week while we were overseas. That actually took a surprising amount of legal jiggery-­ pokery due to the sensitive commercial nature of her work and the fact she’d be bringing a work laptop with her. Some people cannot work remotely from certain countries; fortunately, Croatia is OK, being now part of the EU. The morning of our departure, a neighbour was to drop us off at the airport. We were lucky we didn’t have to be at the airport at some ungodly hour, so we had some time to relax. This spare time was important, as when the neighbour came to pick us up and I loaded our bags into the boot of his car, I caught one of the straps holding his folding rear parcel shelf and popped the plastic bung/holder from its anchor point. No matter; I should be able to simply pop it back in. Except I couldn’t because it had broken off, and the flexible expanding base part that would usually keep the mount in its hole was half missing. Great! Feeling sheepish about breaking his car, I realised that the bungs were very similar on our own car, so I fumbled through our luggage to find a key, politely avoiding his objections that he’d fix it, and pulled one from our boot. It was almost the same in looks and the same size, so I popped both from our car and replaced both in his car. Problem solved; I’d get new ones when we got back. So, job done! Just plane broken At the airport, we boarded our flight only to be told the entertainment/media screen on my seat was not working. The flight to Singapore was quite full, and the ‘fix’ the purser offered was that if I wanted to watch a movie, I could go to an empty seat way down the back in cattle class. That is obviously less than ideal, and I was not that pleased. We faced an almost-12-hour flight, and without a book, I’d only have my wife and my phone for company unless I sat at the back of the plane. The engineers had apparently been trying to fix it during the turnaround but ran out of time. The start of this trip was not looking promising! While everyone else was boarding, I looked over the screen in this Airbus A350. It was pretty big compared to what I was used to. The trim around it hadn’t been pushed closed properly, so like any good inquisitive serviceman, and against my wife’s protests, I gently unclipped it all the way and removed it. I know I shouldn’t have, but in my defence, they had left it like that, and I couldn’t help myself to take a look. 92 Silicon Chip Australia's electronics magazine siliconchip.com.au Items Covered This Month • • • • A servicing free holiday (not!) Bringing a mobile phone battery back to life Repairing a Zodiac pool cleaner Pfaff sewing machine repair Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com There was not much to see underneath anyway, but I did notice one corner of the screen’s frame hadn’t seated back in properly and was protruding by about 1-2mm. This could be why the trim hadn’t fitted flush like the rest of it. Now, stressing screens like this isn’t a good idea, even accidentally, but it appeared OK, with no obvious cracks. I’ve seen enough cracked internally after being flexed even less than this, though, so I didn’t hold out much hope. Regardless, I gently pushed on it right over the metal-framed edge and increased my pressure until I felt it click back into place (or break, I wasn’t sure which)! The boarding hullabaloo around me ensured that what I was doing wasn’t apparent to anyone other than my by-now horrified wife. Still, suddenly I got a message on the screen simply saying ‘rebooting’, and a progress bar told me it was almost done! I replaced the trim surround, and after the screen went blank for what seemed an agonisingly long time, up came the KrisWorld entertainment menu. I was pleased I wouldn’t have to change seats, and I hoped that the thing would hold out for the whole flight. Like so many of my repairs on stuff I know nothing about, it was just dumb serviceman’s luck and a complete fluke that it was now working. That reminds me, I should send my invoice to the airline... Fortunately, the rest of the flight went without me having to repair anything. We had a decent layover in Singapore, but not enough to leave the transit area. We found a lounge, paid our entry fees and parked up, partaking of the comfortable seating, endless buffet and bottomless drinks menu. The problem with bottomless drinks is the frequent need for restrooms. I made my way to the closest one, but it was closed for cleaning. That wasn’t a problem; in Terminal 3 at Changi, plenty of others are a short walk away. As I went to find one of those, I noticed through the open door a cleaner appearing to struggle with a floor-cleaning machine. did feel slogged out. I took the strain out of the connection and moved the cable into several positions while hitting the switch. The machine fired up with it in one position, but it stopped again after letting the cable go. The strain reliever where the lead entered the plug and the cable itself didn’t look stressed, so I assumed it was the plug. Physically moving the plug with the power switch on resulted in the motor kicking and stopping. So, the plug and/or socket, then. I looped the cable through one of the handles on the machine’s body and tied a knot in it, taking any stress off the connection but holding it in a position where power made it through. The machine fired up and stayed running, even with moving it around. There was no obvious burning or arcing at the socket. Not ideal, obviously, but she was relieved that at least she could finish this job, open the loos and then have the service guys look at it properly. I even got to use the toilet, so a reward in kind! Amazingly, nothing needed fixing for the rest of the two-day journey. I guess there were some things, but by that point, I was so sick of airports and lounges that the place could fall down for all I cared; I just wanted to get to our destination. I’ll wager I’m not the only traveller who greatly rues that we haven’t yet perfected a Star Trek-style transporter! Wife needs WiFi Reaching our final destination threw up some other challenges. It seems that once they knew we were coming, they started making a list of what I might be able to help them out with! While it’s nice to be wanted... Of course, the first thing we’d want to do is get connected to the internet. We couldn’t, at least not in the part of this partitioned house we would be staying in. The solid concrete and reinforced steel walls of these typical Croatian homes seem impervious to WiFi signals! That meant going to the other part of the house if we wanted any WiFi connectivity. Servicing around the world This thing looked like a mashup of an industrial vacuum cleaner and a floor cleaner/polisher. She was switching it on and off, and it seemed to be trying to start but failing. Exasperated, she gave up. Again, the Serviceman’s Curse stepped in, and I walked in and asked if I could help. She was very grateful and gladly accepted. I noticed as she operated the switch on the side of the machine, it rotated slightly with the pressure, pulling on the power cable. I suspected there could be a break in the power lead, or the machine’s socket and plug might be contacting intermittently. I checked that the plug was hard into the socket, but it siliconchip.com.au Australia's electronics magazine July 2023  93 It would do for a day or so, but something needed to be done as a long-term solution. Regular readers may recall me talking of this same scenario five years ago; work has been done on this house, and my previous repeater setup had been dismantled. Due to the new construction, that option was no longer available. Running cables by drilling holes in walls is a big no-no! We browsed the local computer store and purchased a decent long-range router; I wish hardware were this cheap in New Zealand! I may even take it home with me this time. Our only option was to run a cable from the existing router in the other part of the house up along the corners of rooms and tops of walls and down along the skirting boards. I would be taking full advantage of some gaps underneath doors, which were opened ironically due to a good earthquake here a few years back. The new router would be positioned on the dusty top of a cupboard just through the wall from where we’ll be spending the most time. This arrangement gave wider WiFi coverage and allowed us to get some reasonable speeds, although it maxed out at 30Mbps down and 5Mbps up. That’s a long way down from the 980Mbps down and 600Mbps up we usually get back home! Even then, my wife could not reliably use Microsoft Teams for her work, which was a major roadblock. We worked around that by buying a local data-only SIM for my dual-SIM Samsung Galaxy S22 and setting it up as a mobile hotspot. That gave us some excellent speeds, as this town’s mobile coverage is pretty good. She no longer has any problems doing her work, and I can surf the web and email, so that’s another couple of fires put out! They knew we were coming Many people here own what they call a beach house. This family is no different. In reality, these are more like apartments and the coastline is covered in them. Some have just one apartment for the family, while others have several that are rented out during the season to some of the millions of tourists who flock here every summer. 94 Silicon Chip Our visit, just pre-season, coincided with my mother-in-law going to her beach house to prepare her two apartments for guests. As you would surmise, these places sit empty for eight months of the year and, being by the seaside, nature can be harsh. Though pretty tightly locked and sealed against the elements with the amazing shutter and window systems they use here, most places need frequent maintenance. A repaint every few years is essential, and any metalwork such as railings and fittings (of which there is a lot) must also be sanded and painted. I did a lot of that last time and wasn’t overly keen to do more, but apparently, there was a problem with the TV in one apartment and the mains power in another. I could probably handle the TV – the mains power, well, we’ll see. The culture here is very much DIY or helped by your mates, with calling in a professional an absolute last resort. All the family members who could do this sort of stuff have moved on, so if I’m around, I’m tapped on the shoulder. The part of the coast the house is located is about 30km from where we are, over a very narrow road over the hills (although it’s infinitely better now than before). Once there (still nerve-wracking after all these years), I got into sorting the TV. It’s a wall-mounted flat screen, about 50 inches (1.27m) diagonally, and made by some local brand, likely stuffed with Blaupunkt or Phillips hardware. I’m guessing they are similar to the cheaper no-name brands the appliance stores sell back home; those usually have a well-deserved bad reputation for quality control. I’ve worked on a few back home, and I was hoping this wasn’t anything too serious this time. Due to the relatively low cost (for us tourists), it is often easier just to buy another one, but that seems to be against the ethos of many older people here! The TV powered on, but its reception was terrible. All the TVs in the block (three in different rooms) shared a common antenna, on the roof, of course. Cabling came down from the antenna and was embedded in the walls when the place was expanded upwards of 10 years ago. The antenna Australia's electronics magazine siliconchip.com.au points are screwed to the wall, and each TV connects via a coaxial cable and standard Belling-Lee plug. The TV reception in the top apartment wasn’t too flash either, so it was most likely the antenna. Great; I’m not good with heights, and the ladder system to reach the roof is rickety at best. Still, with the ladies watching, I couldn’t very well leave it at that, so up I went. I was fine once I was up there, except the typical red terracotta tiles were already so hot, so I couldn’t stay in one place for long. Luckily, it is relatively flat, as is typical in many temperate climates (average temperature here: 19.7°C). As you’d expect, the antenna was a feast of corrosion. I cleaned it up as best I could with sandpaper, stripped and reattached the cable at the terminal box, and reports from below claimed all TVs worked perfectly. The mains issue would have to wait. I was baking and needed a swim. This is our holiday, after all! Bringing a battery back to life J. W., of Bairnsdale, Vic was prompted to write in after reading the contribution by D. M. of Toorak, Vic in the Serviceman’s Log of December 2022, about reviving a lithium battery that had been over-discharged... I had a similar problem when I wanted to use a mobile phone that had been sitting idle for a while. There was no power and the phone would not charge. Since the battery was removable, I took it out and measured no voltage between the terminals. I’m a bit of a miser and didn’t want to spend the money on a new battery if the old one could be salvaged, so I had to be careful how I proceeded. My repair attempt would be no good if I destroyed the battery trying to open it. Some slow and careful probing, along with persistent levering, allowed me to separate the plastic divider on the negative side of the battery from the battery. I managed to do that without breaking the connection between the battery and the protection circuit, which was housed inside the divider. Further probing with a multimeter on the exposed cell terminals revealed that it was down to less than a volt, which was obviously far too low. With little hope in my heart, I nevertheless connected a regulated power supply to the cell terminals, set for 4.2V and, keeping the current limit low for safety, applied 500mA and then monitored the battery closely for signs of distress while it charged. Around two hours later and with no signs of distress, the cell was showing around 3.2V, so it was probably time to use the proper charger to finish the job. I closed the battery and inserted it into the phone. Although it was a little snug due to my ‘surgery’, it did fit. I connected the charger, and the battery took a full charge. It’s a wonder that the battery recovered, but I’m happy with the result. I won’t be entirely trusting that battery since spending some time at such a low charge level may have damaged it internally. Still, it seems that under-­voltage may be less of a concern for lithium batteries than over-voltage is. I saved approximately $50, which I otherwise would have needed to pay for a new battery. Pool cleaner motor repair R. S., of Fig Tree Pocket, Qld has been busy fixing (among other things) a pool cleaner... The Zodiac VX55 pool cleaner motor block has three motors: two geared ones for the wheels, plus a large one to pump water through the cleaner. There is also a circuit board that powers the motors. The wheel motors are each driven by four Mosfets, two N-channel and two P-channel so that they can be driven forwards and backwards. There is one N-channel Mosfet to drive the pump motor. A three-way cable feeds the motor block with 30V, Earth, plus a bidirectional data line from the external controller. The data line is serial, with commands sent from the controller and any error messages returned to the controller. If the controller cannot communicate with the motor block, it displays Error 10. The Mosfets can go short-circuit, and this will give a ‘motor shorted’ error. These can be replaced, but water leakage into the motor block can cause board corrosion. Clean the board if you can, or try to get a replacement on eBay. Also check the motors by powering them with an external supply. When you put the motor block back together, use a water seal compound; otherwise, the o-ring will leak. Sewing machine repairs B. M., of Powranna, Tas is usually a little reticent about diving into the unknown, especially mains-powered devices. Still, living in the country, he sometimes must tackle things he otherwise probably wouldn’t... Among the fixes I have undertaken since Christmas are two of my wife’s extensive collection of sewing machines The Zodiac cleaner body (left) and the main PCB that controls the motors (right). siliconchip.com.au Australia's electronics magazine July 2023  95 (she has many but still complains about my collection of toys etc!). The first was a computerised Pfaff, Model 1473CD, from the mid-to-late 1980s. She bought this second-­hand many years ago, so we know little about its history. It carries a label to the effect that it was made in West Germany. The Berlin Wall came down in 1988, and the two Germanies reunited in 1990, so it was pretty easy to date this one. It had seemingly died, the display remaining unlit and the motor refusing to start. I immediately suspected electrolytic capacitors, as the machine hadn’t been used for a few years. I persuaded her to leave it powered up for a few hours in case the electrolytics needed to reform. Sure enough, the next morning, there were signs of life on the display, and she could select a few of the 168 stitch patterns from the controls. It also started to run, although very slowly, and it wouldn’t stitch in reverse. Still, she was encouraged by the progress as it had been one of her favourites way back. So, there followed a further period of leaving it powered up to see if further capacitor reforming was possible. It was; many more stitches could be selected, and it looked like a very simple fix. The trouble was, the next time she tried it, all seemed OK until she stopped to have lunch, leaving the machine powered up. During lunch, we heard it start up and slowly start stitching away, all by itself! That struck me as a risky failure mode, but there it was, happily sewing some imaginary fabric with no operator within cooee. Time for some web research by yours truly. As suspected, I found a lot of reported instances over the years involving this behaviour with this model and several others in the Pfaff range. Most had been met by advice that the control board required replacing; of course, it is no longer available. Then I found one post that agreed with my suspected diagnosis, even identifying 22μF electrolytics as the likely culprits and suggesting that the faulty machine be taken to an electronics repair shop, rather than a Pfaff agent, for their replacement. That persuaded me to take the machine apart. We did find a repair manual for it online, but there was no circuit diagram included, just a note that the board should be replaced entirely. The only thing to do was to take a look. Getting at the board was as simple as undoing a few screws and removing a plastic base. A few more screws released the board from the metal machine frame, then came the unplugging of myriad cables. Talk about nostalgia. On turning the board over, I was greeted by a linear power supply, including the transformer, three 8-bit micros and numerous other chips, all clearly bearing their maker’s brand and type numbers, plus the typical range of discrete components. Best of all, it was all through-hole! There were five radial 22μF electrolytics to bypass the supply lines to the digital chips, a 4700μF 16V axial type to filter the supply for the digital chips and a 2200μF 63V axial in what I assume was the supply for the motor control circuitry. I could see no evident distortion on any of the caps. Still, as I had a few hundred 22μF caps on hand from several cartons of components I had bought from the family of a former TV serviceman back around 2005, I replaced them all (my wife also complains about my hoard of parts despite my insistence that they will all come in handy one day!). 96 Silicon Chip The originals were rated at 6.3V, whereas my stock was all 16V, but I thought that should be OK. To my surprise, I didn’t have anything approaching 4700μF in axial form and nothing at all in higher voltage axials for the 2200μF. I wanted a few other bits but couldn’t see them in stock at element14, so I looked at Digi-Key, despite some bad experiences buying from overseas in the past. I noticed they match the free shipping on orders over $60 from element14 etc. They had all the parts I required in stock, so I ordered from them on Tuesday morning. I was stunned to receive the package on Friday morning, having come from the USA via UPS and then the final delivery into my PO Box by AusPost! With the bits on hand, replacing the two remaining capacitors went smoothly. There was also some corrosion on the board from a pair of AA cells that obviously supplied the memory backup (no flash etc in those days). Cleaning that away just left discolouration on the tracks where it had eaten through the solder resist. After reassembling the machine, I took the precaution of warning my wife that, again, the electrolytics might take some time to reform, especially the 22μFs from my stock that I knew had to be probably 30 years old. Sure enough, on powering up, only the work light came on, so we left it powered up. About an hour and a half later, I walked past the machine on the way to the kitchen and saw that the display was now alive with a series of numbers that meant nothing to me, so I called the cook. She immediately recognised them as stitch codes, so she sat down to explore some more and finally, fed in some fabric and stepped on the foot pedal. The machine immediately sprung into action and produced the selected stitch pattern. I think she then tried all 168 available and declared herself very happy! She later went onto one of her international sewing groups to tell of my miraculous fix and got swamped by queries from others with similar dead Pfaffs. I was just happy that the fix had proven so simple and cheap, even if I’m still not sure if the caps were the problem, or whether it was the corrosion. Anyway, it was a machine saved from being junked, and I enjoyed the brief period of hero status, knowing it couldn’t last long. Incidentally, I also came across reported instances of other brands of sewing machines from that era having similar symptoms and similar solutions. The second fix concerned a Husqvarna Huskylock 910 overlocker machine from 1997. I knew the age of this one The Pfaff sewing machine control board. Australia's electronics magazine siliconchip.com.au as we bought it new at the local agricultural fair not long after buying our property here. Of course, it had also been declared as her favourite overlocker and required fixing, despite the presence of at least three other overlockers, including another recently acquired model 910. Editor’s note: an overlocker is a special sewing machine used for cleaning up edges or forming tidy seams between pieces of fabric. The favourite had died mid-stitch last year when the motor slowed dramatically and then stopped entirely. I immediately thought it was probably the brushes, a very dirty commutator, or maybe the bearings. The motor is, of course, buried deep inside the machine, so major disassembly was required. I’m always worried when tackling plastic cases, as they seem to quickly embrittle, and bits are likely to break off, usually right where the fasteners go. In this case, though, it came apart fairly easily, so the motor was soon out. The brushes looked fine, so I disassembled the motor. The commutator had a bit of crud on it, but not enough to prevent the brushes from doing their thing. I polished it anyway, then took a close at the windings. They looked OK, with no sign of overheating etc. So, out with the multimeter. The windings were fine, so it was on to checking the brush holders and their wiring. Only then did I notice a small component in series with one brush holder. It measured open-circuit. I took it out to find it was a 150°C thermal fuse that hadn’t appeared in any of the videos I had seen on YouTube. It was rated at 2A/250V. A check of Jaycar’s catalog showed their nearest thermal fuse at 158°C and 10A. The catalog gave the physical dimensions; it was larger but looked like it could fit, so I was off on the 60km roundtrip to buy some. It was indeed a bit of a battle to fit the fatter fuse in so that it didn’t interfere with the armature, but I was confident it would do the job, and the extra current rating wouldn’t hurt. I couldn’t see any risk in it blowing 8°C degrees higher than the original. There was no trace of heat damage elsewhere in the motor, so I think it just failed rather than doing its job when the motor overheated. So it was another successful fix at the grand cost of $3.95 plus time and fuel costs. The second win was that I only had two surplus bits left over after re-assembly the first time, none after the second! Yet again, I had a happy wife, but I should have known better. She has since lined up other sewing machines for me to look at, including a four-thread embroidery device. I’ve had to search for a special needle-height setting gauge to get it back to being four-thread from its present unhappy three-thread status. Then there is another Husqvarna machine where I will probably have to salvage a 3.5in floppy drive from an old PC to get fully operational again. It is currently with the serviceman who aligned it in late December, but the floppy was not working on its return. It had been before his service. Luckily, I still have one out in storage. Then there is a clutch of much older, purely mechanical machines; I hope the problems only turn out to be motor related. To think that I knew virtually nothing about sewing machines just a few weeks ago, other than we had a lot of them! SC siliconchip.com.au Australia's electronics magazine July 2023  97