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SERVICEMAN’S LOG Use the force, Dave Dave Thompson Over the years, I have built and repaired some weird and wonderful things. These items are not necessarily electronics-related, either. But none of that prepared me for what showed up on my workbench this month. F or example, I have built a car from the ground up. I have made my own furniture, musical instruments (many, many guitars, mandolins and violins) and solid-state and valve amplifiers to make the instruments louder. I have made my own microphones, bugs, radios, computers, Theremins and myriad other hobby electronics projects in between, mainly described by the likes of Electronics Australia, Silicon Chip, Electronics Today International and all the British magazines of the 1970s and 1980s. I have also repaired hundreds, if not thousands, of devices, from mechanical repairs to purely electronic fixes. As you can imagine, this has been far more rewarding than merely being an IT guy, though that business has allowed me to indulge in all those other things. I have repaired TVs and VCRs in Australia (which gives you an indication of when I was there last!) and computers and various other devices in England, Austria and Croatia. Still, in all my years of doing this work, I have never repaired a lightsabre! I know. I can hear your gasps of excitement from here! But, full disclaimer, and somewhat sadly, I must advise that these are not ‘real’ lightsabres. I can hear your groans of disappointment from here. Real lightsabres are 92 Silicon Chip military-grade, highly classified and, as such, are very closely monitored by the government because those things can be really dangerous! If one isn’t careful, someone could lose a hand! The purple ones are especially hazardous and must be treated with great caution. These two in the workshop are just civilian-level lightsabres. Even if modified (which I would never do, of course), they will not take a leg off, cut burning swathes through spaceship hulls or slice open the belly of a tauntaun on the frigid surface of ice planet Hoth. I know this is disappointing to many, but they are only for training purposes, and are designed to avoid the catastrophic injuries typically associated with the real ones. Toys vs the real deal Many of you will have seen these toys in the stores and may have even bought some for the grandkids. Generally, they are nasty, lightweight, cheap plastic things. The best they do is flash a few LEDs down the soft translucent plastic tube that is supposed to be the ‘sabre’ part of the device. A few even make it look as if the blade ‘grows’ longer by using strip lights, an effect that usually only works in complete darkness and with a lot of imagination thrown in. Typically, kids have these things bent and broken in minutes because it is almost impossible to resist the urge to smash them against each other (if two are available) or into household furnishings. This generally destroys them pretty quickly, because they are not designed for that sort of action (even though it’s the first and only thing a kid will want to do when they get hold of one). I remember being in a play at primary school wherein I was cast as a pirate. Dad made me a sheet aluminium ‘cutlass’ style sword with a timber dowel and insulation-tape handle to use as a prop. He warned me that it was pretty weak around the tang (he used the word handle), so I shouldn’t hit anything with it. You already know what I did, the first chance I got. In my defence, it’s a natural human reaction. Of course, I hit something and sheared off the blade from the handle on the first strike. He wouldn’t make me another one, so I learned a lesson that day. I did the play with a plastic one, and keenly felt the difference and his disappointment! So, there’s a massive difference between the lightsabres on the market. Some are for kids and don’t/won’t last, while others are a little more adult, better thought out and might actually make the grade. Australia's electronics magazine siliconchip.com.au Items Covered This Month • Stress testing your electronics • Shining a light on an intermittent LED magnifier • The beeping and oscillating fan • Repairing a gifted extension lead 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 Nicely made but not robust The two that turned up in my workshop recently were of the latter variety. These devices were heavy-duty and very well made, the best I have ever seen. They hailed from China (where else) and were not overly expensive, given their build quality. The handles were substantial and hefty, about 200mm long and 25mm in diameter. They were made from beautifully turned thick aluminium stock, anodised in black. A small speaker was mounted within the tube handle right at the bottom, protected by a fine steel mesh. If you can recall those ultrasonic transducers we used to experiment with back in the 80s, you’ll be able to picture what this speaker looks like from the bottom. At the other end, a very shiny parabolic-shaped reflector is embedded in the top end of the handle. This contains a super-bright LED array, in monolithic form, mounted right in the centre. Along the top of the handle, where your thumb would naturally sit, is a solid push button, which switches the device on and off. Just below that is a charging port, a standard barrel connector that uses a lead (which comes with the devices) that plugs into a suitable USB phone wall charger. These sabres have heft and certainly looked the part! I didn’t see the extended polycarbonate translucent ‘blade’ part, as the client had already removed those for easier transport. In my opinion, that is the hardest part about replicating a lightsabre. Most just don’t look right. The typical frosted plastic ‘blades’ are not convincing, and some of the toy versions I have seen even have an extendable blade system (like an old transistor radio aerial) that is supposed to mimic the blade ‘growing’ out of the handle. They are usually inherently weak and next to useless. My customer reported that his son, who owned these sabres, also practises kung fu. Kung fu features all manner of blade work; it’s basically an umbrella term for any Chinese martial art. It seems the son and his friend had staged some full-contact combat using these toys, and suddenly, both had stopped working. Yikes! I guess somewhere in the Chinese instructions, they advise against hitting anything at all with them, but the very solid construction likely gave the guys a false sense of security as to how far they could push their swordplay. I know the feeling; after 25 years of Aikido, I was pretty tough on my timber training swords, requiring me to replace them every few years because splinters can really hurt! siliconchip.com.au Because the acrylic ‘blade’ parts had been removed, it was a lot easier to work with them on the bench. My bench looks like a grenade has gone off anyway, so not having to deal with anything but the handle part of it was a relief. Getting them apart Small grub screws held everything in, and it was clear that someone had had these apart before. Several of the screws had their threads stripped in the aluminium housing, so they just spun and wouldn’t come out. One had been cranked in so tightly that it had distorted the speaker casing. It’s never good to get things in for repair that someone has already had a go at. Never mind, there was nothing that couldn’t be undone, so far anyway. The button and charging port on the handle had a couple of domed Allen screws holding it into the handle. I guessed there would be a PCB in there that held all the electronic components. I took out the grub screws holding the speaker and those holding the LED lens assembly completely, and when the button screws were removed, I could slide the whole caboodle out of the case. I was impressed with the build quality of everything I saw – someone had put some real effort into designing this ‘toy’. Once I had all the gubbins clear of the case, I could also appreciate how much they’d managed to cram into it. It all came out as one ‘string’ of components, with the LED assembly at the top end, then the PCB, then the battery and finally the speaker. Everything was inter-wired and taped together. It was very well made. My first port of call was the battery. I know some of these rechargeable 18650 cells can be a little shonky in Chinese gear, so it was out with the multimeter to see what was going on with it. Sure enough, it was flat, reading just under 1V – very low. The customer said they might have been sitting around a while, so I broke out my bench power supply to give it a nudge. As soon as I connected the ad-hoc charging cable I’d made up for it, I was rewarded with a bright green light from the LED, which I guessed was a charging indicator light. That was a good sign. After a few hours of pumping 5V at 250mA Australia's electronics magazine August 2024  93 into it, I pressed the button and was rewarded with a screeching sound from the speaker and a bright light from the other end. I suspect that sound is the sampled sound of a lightsabre firing up. As you can tell, I don’t watch many Star Wars movies! Pressing the button sequentially changed the LED colour and a few of the sounds. I think that when the acrylic ‘blade’ was attached, this would look quite cool with all the different colours and levels. The LEDs used dimming effects, going brighter and darker to simulate starting up and shutting down; that’s quite clever, and when you include the sounds, the experience is quite immersive. I have to say, while these LEDs were not lasers, they were exceptionally bright. I couldn’t look directly at them – a mistake I made just once. I don’t know whether they had some tricky circuitry on the board to boost the battery’s output, but overall, the single 1800mAh cell did a pretty good job of making this thing shine. So, the battery was flat on light sabre number one. Hopefully, number two would be just as simple. A tougher nut to crack While I charged number one’s battery, I disassembled number two. This was the one with a distorted speaker housing and a few stripped grub screws. I plugged my second power supply into the charging port (using crocodile clips as my charging lead was already in use) and initially got... nothing. Hmm. The battery measured less than 0.3V and was likely too far gone even to be chargeable now. The critical level is usually around 2V. I unplugged it – the batteries on these devices are connected using those typical little white twopin connectors we often see, usually called JST connectors. This makes it easy to swap things over. 94 Silicon Chip I sat number one alongside number two and plugged the battery from one into two but still nothing happened. Obviously, there was something else going on with number two. I placed number one’s battery into its chain and set it aside to let it continue charging – hopefully, that one would return to its normal capacity with a little love. I ‘zapped’ the battery in number two just to see if I could resurrect it. I also ordered a new one in case I needed it. However, despite my best efforts, I could not get much life from this battery. I could bring it up to voltage, but I just couldn’t get any capacity out of it. Swapping things around the other way, battery two in handle one, it would fire up, but it would be flat in a minute. The number two sabre itself still didn’t work. It lit up with a flickering green charging light with the power supply at a very specific voltage, but it just wouldn’t do anything otherwise; pressing the button had no effect. I tried bridging the switch connections on the PCB, in case the actual switch had failed, but to no avail. Hmm... I went over it under the microscope, looking for cracks in the printed circuit board or other physical damage, but I could see none. It is a wafer-thin multi-layer board; I guess they don’t want to waste any more material than they absolutely have to. Given the complexity of the board, there could be any number of problems with it. The PCB is packed with SMDs and all the part codes had been ground off the chips, which is so typical of this type of product. siliconchip.com.au I couldn’t see anything inside that might be affected by impact damage. There were no apparent cracks, components fallen off or wires disconnected. It just didn’t work. I suppose that, given time, I could have swapped PCBs and other ancillary components between the two, even at a board level, but I had to accept that number two was dead. I did swap speakers to check that the bent one still worked. Once I confirmed it was working, I used a pair of vice-grips (suitably taped up to avoid leaving any marks) to gently squeeze the speaker back into a rounder shape. It seemed a moot thing to do, given that the sabre itself didn’t work, but it needed doing, so I did it. Fix or do not fix, there is no try Sadly, with no circuits, no information online or even any idea what the ICs were, there was not much I could do except make sure the first one’s battery was up to spec (which it seemed to be) and to chat with the client about charging them up. The charging lead came with the sabres, and it is designed to be used with a phone charger. The problem is, as I’m sure you can all see, is that there are several flavours of phone chargers. The one the customer was using was a little weenie, but he did have one that stated 2A output, so I advised him to use that one. The smaller one may have eventually charged the batteries, given time, but when it comes to playing with swords, especially ones that make noise and flash when you hit them, there is no time like right now! I reassembled the electronics into the handles, once again marvelling at the attention to detail. For example, the speaker had an O-ring, which sat in a groove around the circumference and not only isolated it acoustically but likely physically as well. I doubt it was for water-proofing – civilian-level light sabres do not work under water – so it must be there to provide some damping from whatever vibrations or shock might befall it during use. So, mixed results then. One is up and running; the likely problem was that the charger being used wasn’t supplying enough juice to keep the battery charged. However, with the second one, my guess is that it’s an internally cracked board. Some of it seemed to work (for example, the battery charging circuitry), but something prevented the rest from powering up. Sadly, that was about as far as I could go without exceeding the cost of simply buying another one. Nobody wants to pay hundreds to fix a $50 device. Still, at least he still has one very cool, working lightsabre! 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. However, it has been playing up for the last year or two. After switching it on, it would work normally, but after a few minutes, the light would dim or go out. Switching it off and on would sometimes result in it ‘resetting’ and working fine for a bit longer, only for it to go out again shortly after. This intermittent fault had long puzzled me because my initial diagnosis of it being an overheating component was not supported by the fact that it would sometimes immediately reset once power cycled. A hot component does not immediately cool down when the power is switched off. In any case, after putting it off for way too long, I decided to take a look and pulled it apart, still mounted to the bench but rotated by 180°. It is a 90 LED unit with three curved boards of 30 surface-mount LEDs, each surrounding the magnifier lens, mounted on a removable plastic sub-frame. The three LED boards are connected in series by hard wire jumpers. My initial assumption was that the fault was in the LED driver board. Without the benefit of the magnifier (I later realised I could’ve just popped the lens out and held it!), I checked for obviously faulty joints, but everything seemed in order. Noting carefully which end of the board was at mains potential and which was low voltage, I gingerly felt the back of the board for hot spots. I didn’t feel any, but I must have bridged two wires that shouldn’t have been bridged because the lights went out and refused to come on again! I thought I had really ‘blown’ Jaycar QM3546 LED magnifier repair I hate to throw something away that could be fixed, so I often give it a go, whether it is mechanical or electrical. I am an electronic repairer wannabe with a very mixed hit rate. Needless to say, my favourite column in Silicon Chip is Serviceman’s Log. My Jaycar QM3546 desk-mounting LED magnifier has been a great investment as birthdays flit by and vision becomes more challenging. It was an essential item in my fiddliest repair ever – my mother’s old pot plant moisture meter in which the hairspring had come off. That required the pointiest of soldering irons, the steadiest of hands and the magnifiest of magnifiers. siliconchip.com.au An internal view of the Jaycar QM3546 LED magnifier. The fault seemed to be temperature-related. Australia's electronics magazine August 2024  95 it this time. But after leaving it and coming back later, the lights came on, bright at first, then dim. After unscrewing the PCB, I noted that the one large 100V 100μF electrolytic capacitor was not bulged or leaking. I considered desoldering a leg to test its capacitance and ESR, but first, I looked online to see if I could buy a replacement if it was a dud. Dishearteningly, I couldn’t find an exact replacement. It was time to remove it from the desk to do some proper checks. After crawling under the desk to remove the clamp and give a contortionist a run for their money, I discovered that I need not have, as the lamp simply lifts out of its clamped socket. Dang. On a spare table, and with the LED sub-board flipped over so as not to blind me, I switched it on and it came on dim. I measured the output voltage at around 47V. I assumed that the voltage must be higher for it to work correctly. As a better test for overheating components, I added a spray nozzle to a can of butane, ensured no ignition sources were nearby, inverted the can, and sprayed the board. The board got cold, but nothing changed; the lights remained dim. Getting the lights to shine brightly so I could measure the output voltage in that condition was problematic and took some time and fiddling. When they finally did, I quickly measured the output voltage, expecting it to be much higher than before – it was the same! If there was no difference in the output voltage as the brightness changed, the fault must be with the LED boards. After switching the lights off and reinstalling the PCB, I flipped the LED sub-frame over and examined them. One LED had brown stains at each end, but after testing it, I found it wasn’t blown and seemed to work normally. I checked it while wearing a pair of welding goggles! I started noticing that the more I handled the sub-frame, the more the lights flickered. I checked and wiggled the main power input wires, but they seemed securely fastened. Each LED sub-board was held in place with three screws, and I removed them now. Since the jumpers were not flexible multi-strand wires, I felt sure that lifting the light boards out of their little cradle would result in breakage, and I would inevitably end up re-soldering something. As I began to raise them, one joint broke almost immediately. Reseating them in the cradle and using a screwdriver to re-make the connection resulted in the lights shining brightly. I screwed the boards back down to prevent relative movement and re-soldered this joint. I deeply suspected that this was the fault all along and not merely the outcome of my disassembly. That was confirmed when the lights came on immediately and powerfully, in contrast to before, when the lights would take time to ramp up and were not fully bright. In the accompanying photo (on page 95), the screwdriver points to the initially faulty connection. After beginning to reassemble it and almost forgetting to include the diffuser/lens-holder, I got it all back together and working nicely above my desk. There were many times I toyed with the idea of discarding this lamp and buying one of the sexy new ones with interchangeable lenses, but I knew that this one would continue to haunt me if I didn’t at least try to fix it, a fix that turned out to be relatively simple. It’s always about giving it a go, taking it slowly, trying to think as logically as possible, eliminating what it isn’t, leading you to what it is. T. M., Capel, WA Lucci Breeze model 213128 fan repair A friend rang and asked me if I could come over and look at her oscillating fan, which was making beeping noises when switched on. The fan was bolted to the wall and could be operated by an infrared remote control. She was correct; when I switched on the power, the fan made beeping noises but did nothing else. So I unbolted it and took it back to examine it on the bench. The fan was relatively easy to get apart, and I was soon looking at a circuit board with a capacitive power supply that had a 1μF X2 capacitor in series with the mains. The capacitor drops most of the mains voltage and dissipates little to no power because the current and voltage are out of phase. Above: the main PCB for the Lucci Breeze fan (shown adjacent) with the 1μF capacitor removed. Keen eyed readers might be able to see that the PCB silkscreen labels that capacitor as 0.1μF. 96 Silicon Chip Australia's electronics magazine siliconchip.com.au This type of circuit is dangerous to work on, as the whole electronics board is at mains potential. So I plugged it into my mains isolating transformer to be on the safe side. It no longer beeped when I turned it on, so I thought it could be an intermittent fault. I measured +5V across a large filter capacitor, so all seemed OK. But when I tried to operate the fan, the +5V dropped to +3V. I have seen this fault many times before where the X2 capacitor has dropped in value, so the reactance becomes too high for the circuit to work properly. I removed the capacitor and found it to be only 170nF instead of the specified 1μF (1000nF). A typical tolerance of such a part is 20%, so it was way out of spec. I had a replacement class-X2 capacitor in my range of spares, but it was physically a bit larger and would not fit under the circuit board where the original was. I had to make flying leads and attach the capacitor to the plastic case around the circuit board, ensuring the system was still well insulated. The fan worked as intended when powered on, with the remote controlling the speed and oscillation. After reassembling it, I returned the fan and reattached it to the wall. My friend was very happy to have her cooling fan going again, as summer was just around the corner. Editor’s note: we often find that replacement X2 capacitors are physically larger than the failed ones. We wonder why! J. W., Hillarys, WA Extension lead repair I was sorting through some items in a box given to me years ago that I hadn’t gotten around to checking when I found a short extension lead. I noticed that the cord-grip nut was missing from both the plug and the socket, so I would have to repair it before I could put it with our other extension leads. I started at the plug end and immediately noticed that the plug was on the wrong end of the cable because the Active and Neutral wires crossed over instead of going straight to their respective terminals. That meant I would have to remove the plug and the socket and swap them. I turned my attention to the socket end and could see that the Active and Neutral wires did not cross over but were connected to each other’s terminals! I don’t know who made this extension lead, but they obviously did not know what they were doing. With both the plug and the socket removed, I fitted them to the correct ends of the cable, along with cord-grip nuts, ensuring that the Active and Neutral wires connected to their correct terminals. I then tested the lead with my multimeter, and all was good. Whenever I encounter an extension lead that is not ours, I always check it to verify that it’s in good condition and wired correctly. This particular lead could have been dangerous in certain circumstances, for example, if some idiot used the ‘black is Earth’ idea (a common vehicle terminology, which isn’t correct either). I remember reading a Serviceman’s entry in Electronics Australia decades ago, where a similar situation existed with a live PA system. If you don’t know what you are doing with mains wiring, it’s best to leave it to someone who does. B. P., Dundathu, Qld SC siliconchip.com.au Australia's electronics magazine August 2024  97