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SERVICEMAN’S LOG Going straight for the jug-ular Dave Thompson Home appliances – I love them! So much, in fact, that I have plenty languishing unused in cupboards and often have to have a clear out to make room for more. They make life so much easier for most of us. While the rock stars of the appliance world, such as ovens, refrigerators, dishwashers, washing machines and dryers, all make our usual chores faster and more efficient, it is the unsung heroes that can really make a difference. That’s the backing band of kettles, juicers, mixers and vacuum cleaners. These guys all get a thorough thrashing in the typical household, and are equally stars of the show. We all know that appliances are not made to last anymore; it seems nothing is made for a long service life these days. Still, so many of them are inexpensive and just ‘do the job’. For example, I can buy an electric jug from the local ‘mart’ (insert shop name here) for less than $20. These plastic fantastic models work well and do what they say on the tin – they boil water. Once the plastic taste is boiled out of them, they will give years of service, until they have boiled dry one too many times, or simply get too manky to clean anymore. When that happens – and it will – it’s no big deal to just go and buy another one. Rinse, wash and repeat ad nauseum (and ad infinitum?). These cheap jugs are perfect for a student doss, a worksite, or down in the shed; there is nothing wrong with these ‘consumable’ products. Back in my day, when I walked to school in the snow, bare-footed (and uphill both ways!), my parents ‘invested’ in appliances like a kettle or a bench mixer. Yes, they were more expensive than they are now, and it is true we had limited choices, but these things were well made and built to last (for a lifetime in some cases). The business model was similar to that of a car. By that I mean that you bought the appliance once as they had been made solidly and with longterm use and eventual repairs in mind. There was a backup network of agents, dealers, repair guys and (more importantly) lots of spare parts available, with the intention that their product would provide householders many 84 Silicon Chip years of service and last as long as it was still sensible and viable to repair them. And when you realised that company made good products, presumably you went back and bought more of them, since you wanted your stuff to last. Alas, that effect must not be too strong, because even legendary companies like Toyota seem to be giving up on quality being a selling point (or at least are struggling to maintain consistently high quality these days). My mother had a benchtop mixer made by a well-known brand. She had it for more than 30 years, and Dad kept it going with a bearing here and a motor armature there. Things wear out, especially if they are being used. The point is that he just got onto the agent and bought the parts for it; it was relatively easily repaired. We can still get parts for that mixer even now! But I digress. We’d been through many cheaper electric jugs and decided to splash out on the latest one. It’s a known brand, and while pricey, it is designed, built and supported according to the principles I mentioned above: aesthetically pleasing (and very retro), can be fully disassembled and the parts replaced, and those parts are available worldwide (more on this later!). The company has been around since the early 1900s, so they’ve obviously worked out how to do it well and in keeping with the old-style business model of building things to last. So if it does fail, we can simply repair it. I’ve actually written about this particular jug before (a while ago), where sometimes it wouldn’t ‘reset’ after it had boiled, in the September 2020 issue, starting on page 64 (siliconchip.au/Article/ 14575). Anyway, it eventually settled down and never did that again. However, a short while ago, it started not switching off when the water boiled. While it does seem to take a little longer than some kettles and jugs I’ve had, usually after about 10 seconds of boiling, it used to switch off and Australia's electronics magazine siliconchip.com.au Items Covered This Month • A juggling act • The heat gun that got too hot • Repairing an electric cooktop • An electric fence 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 the heating button would click back to its default ‘off’ position. As a test, I let this one boil for a good two or three minutes at a full, rolling boil and it still didn’t stop, so it was time to look into it. The first thing was to get more information. The user manual that comes with it is comprehensive, but doesn’t have much of a troubleshooting section because, well, there’s not a lot to troubleshoot! That section consists of just the basics: Jug doesn’t turn on? Check the power connection and that the jug is seated properly in the cradle, that sort of thing. Obviously, this isn’t much chop at all, so I went looking further afield into forums and user groups in the hope of a service manual. I didn’t find anything, to be honest. The best suggestion, which seems to have worked for some, is to de-scale the appliance. This seemed to me like too simple a resolution. I mean, yes, we all usually need to de-scale appliances, and I’ll admit, in the eight years we’d had it, we had never de-scaled it. Still, I didn’t think we had to if we couldn’t see any obvious signs of scale in the jug. It looked to me to be almost as-new inside. But this is what people were suggesting, so maybe that’s all it was? Perhaps it had clogged up with scale somehow. Of course, I had to then go and buy a de-scaling agent, and there are a surprising number to choose from. There are specialist types for dishwashers, coffee machines, water filters and others, but I only found one supposedly meant for kettles, so that would have to do . I wasn’t about to deep dive into the differences between them all (my hunch is they are likely all the same), so I stuck with that one and got down to de-scaling the jug. Editor’s note: you can also use white vinegar mixed 50/50% with water. Don’t boil it for long; switch it off and let it sit for 30 minutes before emptying, then rinse it thoroughly. Citric acid solution is even better. This highly technical process involves adding the contents of a sachet to the jug, pouring in half a litre of water and boiling it. I let it cool, then tipped out the solution and repeated. This is supposed to break down any limescale or other residues that might clog up the element or thermostat mechanism. This is fine in jugs and kettles that have an exposed element or a sensor inside the boil chamber, but if the element or thermal switch is on the underside of the chamber, it will never get scaly, anyway. To be honest, I didn’t see any difference to the boiling chamber after descaling, and in true fashion, it still didn’t switch off when the water boiled. So, no simple fix for me then! siliconchip.com.au There was no other option but to tear the thing apart and have a look. However, as we were dead in the water without a jug, we ordered another identical one, which was delivered a few days later. I was just hedging our bets; if I could repair the old one (at this point I had no idea if I could), at worst we’d end up with two jugs. Most people would never use two jugs, and I didn’t need two either, so if I did get it working, it would become a spare. It could sit in the cupboard with the other unused machines. But first, I’d have to find out exactly how this one worked. I mean, it’s not complex, but while manufacturers use various methods to control the automatic cut-off, all the ‘cordless’ type kettles appear to use a very similar system. It is simple, efficient and easy to repair, with ready access to whatever element (har!) needs replacing. Of course, different kettles will come apart differently. Some aren’t repairable at all; they are designed to be thrown away, not repaired, and are typically cheap and made of plastic. Luckily, this one is held together like an old aeroplane, with obvious and exposed PK/panhead-style Phillips screws that are all easily accessible. Most hold on the removable bottom cover. Revealing the gubbins is as easy as removing eight screws (some with fibre washers) and involves minimal fettling. I had to remove the on-switch button but then the whole bottom end opened up and this exposed everything I needed to check. As you no doubt already suspect, there isn’t a lot to it. An element, moulded into the metal base of the boil chamber, some fibreglass-coated wiring and a large plastic power socket and switch actuator assembly, which takes up much of the space in the jug base (see the photo overleaf). Of course, all the magic happens in that switch assembly. It is straightforward, meat and three veg technology, but don’t let the apparent simplicity fool you. There’s actually a lot going on in these very clever (and usually reliable) mechanisms. For those who just fill a kettle and switch it on, and don’t know what’s happening in there, here’s a brief kettle primer. In the old days, a metal kettle was put on the gas or electric stove t o Australia's electronics magazine April 2026  85 to heat water, and it whistled when the water boiled and steam started coming out of the small hole in the spout cap. If you left it, it would simply burn dry and be ruined (although that whistle is hard to ignore!). Then someone had the idea of putting an electric element in a kettle body and boiling the water that way – no stove needed. Those old appliances (many still exist) were corded, mains-powered and pretty efficient. However, the exposed elements they used presented problems, especially with scaling, where water impurities harden over time with heat, coating exposed metal surfaces with a hard, white residue. That made the kettle increasingly inefficient over time, not to mention tainting any water boiled in it. Then some bright spark came up with the idea of mounting the element underneath the bottom of the boil chamber, keeping it out of the water and essentially eliminating element scaling. Evolution in action. The next big leap was kettles that switched off by themselves when the water was vigorously boiling. If you forget about it, or get caught up doing something else, your jug wouldn’t boil dry. Otherwise, that would almost certainly burn out the element or even damage the kettle. While some electric kettles had thermostats to help prevent that from happening, the next big thing was already in the works. Soon, along came ‘cordless’ kettles. The term cordless these days usually implies something battery-powered, but in the high-octane world of kettles, this just means the kettle could be picked up from the base that had the mains cord attached, and used without the hassle of a cable dragging behind it as you pour. Despite the sheer number of styles and brands available, the majority of cordless kettles and jugs work in a very similar way. In this one, a thermostat senses the boiling water Most of the space in the base of the kettle is taken up by the switch actuator. 86 Silicon Chip temperature (technically 100°C, though this can change with altitude and water quality), and the power is disconnected automatically while the manually operated switch automatically drops back to the off position. Simple, effective and usually very reliable This jug sits on a circular base unit, which is connected to the mains. When switched on, the switching mechanism connects mains power to the element, which initiates the boiling cycle. When the water boils, steam makes its way down a silicone tube, hidden in the jug’s handle, to the switching mechanism. When it hits the right temperature, it ‘trips’ the switch, disconnects the elements and switches if off. The idea of descaling the jug aims to clear that silicone tube of any scale, which in rare cases can stop it from powering off. Sadly, not in this case. After removing the bottom, I could see a little of the south end of the tube and it looked totally clear. There was really only one possibility left: the thermal switch. This is where the clever bit comes in. Pushing the ‘on’ button sets a plastic swing-arm into a detent (as long as power is applied) and, after connecting the element (and any indicator lights that may be present), it stays that way until it trips off. When setting the mechanism, a bimetal convex (or concave) disc with a hole in the centre for a mounting pin, about the size of a (CR)2032 coin cell, is ‘puckered’ into its non-natural ‘active’ state. When the jug boils, steam is applied to the disc via the silicone tube, and as the disc heats, it simply pops back into its resting state and mechanically resets everything to ‘off’. Simple, yet very effective. Until that disc wears out, which apparently they do. I can ‘set’ the disc and the jug works, and of course I can manually stop it by lifting the switch or taking the jug from the cradle, but it seems that disc won’t return to its default state, no matter how hot it gets. The obvious solution here is to replace that bimetal disc. Unfortunately, that part isn’t available to buy separately. I Australia's electronics magazine siliconchip.com.au mean, they are in general, but I can’t find one specifically for this jug. The only way to buy it is as part of the main switch housing, with the disc already moulded into it. While I imagine there are ways of drilling the plastic centre pin out and replacing the thermostat disc with another, that would require modifying the housing, and there’s no guarantee that would work. There is nothing for it but to buy a whole new housing. My next step was to find a parts supplier in town. I couldn’t find any – although one guy I called said he could order one in, and it would be around $100. That sounded quite steep to me, so I hit the interwebs to see if I could find one elsewhere. Surprisingly, after me talking up the repairability of these appliances, I can only find filters. No elements or switches from their parts outlets anywhere. So, I searched for thirdparty suppliers and found dozens of thermostat assemblies, but nothing that looks anything like this one. Well, that was frustrating. This is a $400 jug, so while $100 plus shipping and tax is likely not too bad for a repair, I still thought I’d be able to get a new switch assembly for less than several times the cost of a whole new cheap jug that includes one! I ended up doing a Google image search and discovered that this looks like a standard Philips part, and I can get one from AliExpress for 20 dollarbucks, including delivery. On closer inspection, it looks identical; all the mounting measurements check out, so I think that’ll do me! It is on its way, and I’m confident it will solve the problem. In the meantime, the old housing is out and on closer inspection, the plastic centre pin is quite worn – I guess the edges of the disc chew away at it each time it is used. Anyway, now we’ll have two jugs! Anyone want a refurbished one for ‘cheap’? Taurus Heat Gun repair Many years ago, I bought a Taurus heat gun from ALDI Special Buys. I’ve used it many times over the years and it has been quite reliable. Just once I had to shorten the power cable slightly after one of the wires broke near the body. Recently, I had just switched it off and put it on the ground when I accidentally bumped it. That somehow switched it back on. I was about to pick it up to turn it off when there was a sudden fireworks display, a heap of smoke and the heat gun stopped. The switch was in the low-speed, low-heat position. I could move it to off, but not to high-speed, high-heat, so it seemed that the switch was damaged. The cheapest replacement heat gun I found was $40, but it had many one-star reviews saying that the case had melted in use. I also ruled out a $50 heat gun that had a lot of one-star reviews saying that it did not even get as hot as a hair dryer; that was useless! So the cheapest decent replacement I could find was $55, and it wasn’t even available locally. Thus, I decided to open up the Taurus heat gun to see what had happened to it. I expected to find everything burnt out, but the damage appeared to be confined to the switch, which was toast. I identified the Active wire coming into the switch, and the low-speed and high-speed wires going to the motor and element. I decided to test the motor and element to see if they still worked. I set things up in a safe way, including a ‘safety switch’ in the mains socket, and plugged the power cord into power Luckily only the switch was damaged when my heat gun stopped working. siliconchip.com.au Australia's electronics magazine April 2026  87 so I could use a jumper wire to connect the Active wire to the low-speed wire. The heat gun burst into life. I did the same with the high-speed wire, and once again, it worked. So it just needed a new switch. I couldn’t find a similar PCB-mounting switch on eBay in Australia, but widening my search to include other countries, I found one for about $8 from China. Further searching using the part number from that result and I found two PCB-mounting switches for $3.99. It took one month for the new switches to arrive. I compared one of the new switches with the old switch, finding that the actuating lever was quite a bit longer and the slider would not sit on the switch correctly. I got my mini hacksaw and, while holding the actuating lever with pliers, cut the excess length off and used a file to smooth the top and chamfer the edges. The slider then sat on top of the switch correctly. But first, I would need to remove the old switch and clean up the circuit board. I de-soldered the old switch and cleaned the soot from the circuit board. I then used a knife to scrape away all the burnt material, leaving a good-sized hole in the circuit board. I soldered on the new switch and used some copper wire to repair the circuit board tracks. With the new switch installed, I reconnected the power cable, reassembled the heat gun and tested it. It was back in working order. So I saved $53 and saved another item from ending up in landfill. Looking further at the destroyed switch, I figured out why it failed. When it was bumped, it was not fully on, with the contacts barely touching, causing them to overheat and arc. Bruce Pierson, Dundathu, Qld. The “Power & Control Relay” board had an IC that looked to have heat stress (the more orange area of the PCB). Electric cooktop repair I was asked to have a quick look at an electric cooktop with ceramic plate heating that wouldn’t switch on. The circuit breaker had been reset a couple of times with no benefit. I volunteered to call in and have a quick look. I checked the cooktop circuit breaker and it was OK. I found the range’s power junction box and determined that mains voltage was getting there. I surmised that the problem was within the touch controls under the glass top. I had to remove the glass sheet to see what was going on, and I discovered two separate PCBs underneath it: the “Touch Control Board” was mounted on top of the “Power and Control Relay Board”. I then discovered a blown 2A fuse on the “Power & Control Relay Board”. Removing the board, I found an IC that had obvious signs Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column in SILICON CHIP? If so, why not send those stories in to us? It doesn’t matter what the story is about as long as it’s in some way related to the electronics or electrical industries, to computers or even to cars and similar. 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. 88 Silicon Chip The application circuit for the TinySwitch III (TNY274280) switch-mode IC. of heat stress around it on the PCB, which you can see in the accompanying photo. In desperation, I tried a temporary fuse replacement, which immediately failed. I thought I would simply go ahead and order a new “Power & Relay Board” but no; there were no spares for this 10-year-old cooktop in Australia on any of the sites I checked on the internet! I then took the cooktop home to start further investigations and unfortunately, the IC that was my suspect had its designations lacquered over. Luckily, I could read a few characters in strong light with a magnifying glass and started a search for a data sheet because this circuit was obviously designed to reduce the mains to 12V DC & 5V DC. It was using an IC that I hadn’t come across before; it turned out to be a TinySwitch III coded TNY274-280. I was able to obtain a new one and replace it. I also replaced the 10μF 450V DC capacitor at the input to this IC that sits across the mains bridge rectifier. While buying the replacement parts, I also happened to find a replacement board on AliExpress, so I ordered one. The cooktop is now working again with a new board, but I kept the old board as a spare. On powering it up after the Australia's electronics magazine siliconchip.com.au repair, I found that its 5V DC & 12V DC rails were present and correct. I don’t know what caused the IC to fail, but I suspect the closed space within the cooktop’s metal housing trapping heat contributed. Paul James, Kanwal, NSW. Electric fence repair (Xstop EL500LEDS) Like my dad, I’m scared of high voltages. I was horrified one day when we walked beneath a transmission line and a spark flew between us when we briefly touched. I think his fears were born from being an electrical operator at a terminal station. Scary things happened when possums tried to walk along a multi-hundred-kV bus! I grew up playing with Kettering ignition, but now as a farmer, high voltages are all around me in the form of electric fences. So you can imagine my dread when my electric fence energiser died. The neon voltage indicators stopped working a while ago, but as long as the shed kept emitting “tac… tac… tac”, I knew it was working. Now, however it was going “tic… tic… tic”, which to my experienced ear meant that either there was a dead short in the fence somewhere (usually a 5km round-trip walk to find out), or that it had carked it. The other indicator of fence failure was half of the cow herd in the house paddock. I’ve always wanted a directional fence tester, and I had hoped that one day a circuit would appear in Silicon Chip. I know testers have been published in the past, but I have long made do with a length of three-core mains cord that had been chewed by my Maremma dog. She chewed in linear fashion from the end, so I had a visual gradation in spark through the insulation when I touched the wire to the fence with the safe end grounded. Sadly, on this occasion, no spark. At least the oscillator was working. So the most likely culprits were the 40μF capacitor or the transformer. I needed to have a spare capacitor in stock in case that was it, so I ordered a couple. After swapping it out, there was still no spark. I had a great deal of trouble finding a suitable transformer; I ended up ordering one from Pakton Technologies, who know a bit about electric fences. The transformer wasn’t a direct swap and required some plastic case reshaping. The primary was easily identified by the heavy copper wires. It was a while ago that I learned higher voltage, lower current, so my secondary had lighter gauge. But there were three wires. I chose the pair with the highest resistance. After a bit of cable extending and connector soldering, I shoehorned it into the case. The neon indicator board had a blown 47kW 1W resistor, so I replaced it with a 3W equivalent I had on hand. In doing so, one of the neons disintegrated, so I had to replace that too. I set up a suitable spark gap and stood at arm’s length from the mains power switch. Upon flicking it, I was rewarded with a satisfying, yet strangely disturbing crack... crack... crack sound. A $150 unit was repaired for $80. Also, it provided some entertainment. My neighbour discovered the fence working after testing at my gate with his gluteus maximus… three times! I don’t think I can count on him testing it again in the near future, and I’m still scared of high voltages! SC Ian Oldman, Budgeree, Vic. siliconchip.com.au Australia's electronics magazine April 2026  89