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SERVICEMAN’S LOG Turning to the dark side Dave Thompson Fear leads to anger; anger leads to hate; hate leads to... suffering broken garden lights? It is that time of year again. No, not the tech column awards (I’ve never been invited!). I’m talking about it being cold, damp, and dark. Down here in the lower southern hemisphere, we are somewhat used to the weather bombs that occasionally circle up from the Antarctic and blanket this part of the country with bitterly cold winds, snow to low levels and lashings of ice thrown in to make things especially difficult. Last year, we were clever and avoided much of this cold and frosty weather by going to Europe, where there was a smoking-hot summer. However, that gets quite expensive, and it takes months of planning, so it is impractical to go every year just to chase the summer sun. On the darkest days here, during June, July and August, even if we have sun, it is barely warm and hangs very low in the sky. A 40W incandescent bulb would be warmer! It is pitch dark from 5pm until 8am. If we get a cloudless night during these months, the mercury drops like Wile E. Coyote in a Roadrunner cartoon, and we get hard frosts well into the negative digits. Usually, when we have an ultra-crispy morning, we have a reasonably nice day. It’s a paltry silver 96 Silicon Chip lining, but it’s better than rain. If it does cloud over during the night, the temperature can drop to zero, and everything will be cold, damp and miserable all day long. This winter, and what remnants of winter we encountered on our return last year, have mostly been about cloud cover and rain. It seems those halcyon days of clear and frosty but dry winter days have gone, perhaps due to climate change or perhaps just because weather is notoriously unpredictable and a pain in the bunions! It also turns out my workshop is leaking, which makes working in it a chore and a potential health hazard, as the carpets are all damp and don’t get the chance to dry out. To be honest, the whole garage/workshop needs bowling and rebuilding. Oh, for a spare 60 grand! Lighting my way My point, as usual a long time coming, is that with all this darkness about, outside lighting is really important. Falling down the front steps would not only be embarrassing but, at my age, potentially damaging. It is more than essential that I have decent motion-activated security lighting and, even better, outside pathway lighting. Most of the old-style Par-38-style security lights were mains powered, so one had to wire them in somehow. They were great, don’t get me wrong. Still, where they are mounted, under the barge boards, there was not always handy mains wiring present, so we usually had to get a friendly sparky to come in and wire the lights in for us (I am legally obliged to say this). My current house was once a single-storey bungalow until a previous owner added a second storey and made it quite large. The problem is that to gain access to areas where security or flood lighting needs to be mounted, I’d have to be rake-thin and as agile as a circus monkey. These days, sadly, I am neither of those things! I once used to crawl around wing tanks in airliners, wiring looms and basically fighting my claustrophobia, but those days are long gone. I was chosen for that task because I was small and thin. All I could do these days would be to use my body to plug a leak! A few years ago, I decided to install some decent security lighting on our driveway and along our pathway. The house is on a back section, down a long shingle drive. The neighbour’s dog does a good job of letting us know if anyone is walking up our driveway with a typical territorial protection Australia's electronics magazine siliconchip.com.au Items Covered This Month • The importance of home maintenance • A modified Crosley radio • Distorted and damaged PA speakers • Repairing the solenoid in a washing machine • Seismograph coil 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 bark. This, coupled with the scrunch of feet on shingles, is usually enough to let us know if someone is visiting. However, in the dark of night, and with my workshop being just inside the gate at the end of the driveway, this often isn’t enough to know if someone might be creeping up there. Strategically placed security lights were the answer. They worked perfectly for the first few years and, once set up, operated with no problems at all. I have two solarcharged, battery-powered units now: one on a handy telegraph pole at the end of the driveway where it meets our yard (a story in and of itself) and one mounted on the corner of the house. I also have a relatively expensive mains-powered unit halfway between the two. I chose mains powered one for this location because I could wire it into my garage without any major hassles. (Or at least, my sparky could!). It is also dazzlingly bright compared to the other two, no doubt due to it having access to mains power. the ladder and climb up to the lights’ locations and have to work on them! I know what you are thinking: I should have carried out preventative maintenance in good weather to ensure they would work over the whole winter. You’d be correct, though it might surprise you that I did just that. When the days were getting shorter and the mercury was dropping, I went around and cleaned the solar panels (on those that used them) and cleared away the cobwebs of the spiders that made their homes in the nooks and crannies of my lights. I also ensured that the Fresnel lenses on the sensors were not obscured by the usual guano, spider webs or anything else that might prevent them from working. While they looked a tiny bit crazed from a few years in the sun, they seemed clear enough to allow things to work as expected. The thermal sensor units are sealed, so there was no way anything could get into them and obfuscate them. The only way they could malfunction is electronically within the electronic gubbins or if the lens was somehow obstructed. Since the lenses seemed clear, I assumed the problem lay inside the units. Time to crack them open The first thing I did was go up and really clean the solar panels of the battery-powered lights. Admittedly, they were a little dirty, but not so much that I thought the lights would not charge. Nothing is built to last any more All these lights feature impressive LED arrays and, when new, were very satisfactory for their roles. Now, not so much. Over just a few years, the polycarbonate frontages have crazed (likely due to the ultra-high UV rays we have beaming down on us here because of the ozone hole – remember that crisis?). The plastic cases inevitably break down and fall apart for the same reason. I guess this is the problem with imported stuff that has not been made to suit our environment. One could argue that, as they are inexpensive, we can just replace them every few years and we can all carry on with our lives, but in my mind, that isn’t the point. If I spend hours installing and setting up something, I expect it to last more than mere months. Perhaps that’s just my naive expectations of how things should be these days, but if I shell out good money (and bigger money for a ‘proper’ security light rather than some cheap rubbish from a big box store), I expect a reasonably long time. My parent’s security lights, installed by my dad at their home, lasted for as long as I can remember. I helped him change bulbs in the latter years, when he couldn’t, but the unit itself worked for decades. So, I have three such lights set up in different positions. As I am writing this, not one of them works. If I go out at 6pm, I’d really like my lighting to come on so that I don’t trip over something in the dark. Of course, when it is freezing and raining and generally nasty weather is outside the window, that is not the ideal time to go and get siliconchip.com.au Australia's electronics magazine September 2024  97 old friends, a bank of 18650 cells. A couple had vented and made a mess of things, so that was likely why it wasn’t working. No problem; a battery swap should see it going for another two years – hopefully – before it completely falls apart. The second one, though, had six D-sized cells. Well, they seemed not quite D-sized. They were odd, and like much of the innards we find in this stuff, had no information on them at all. They would likely measure 1.3-1.5V factory fresh; I’m reasonably sure of that. But now not one measured more than 0.7V. No wonder it wasn’t working. I know they build these things down to a price, but these were more top-line than others, so I would have expected a bit more life from the batteries, at least. Not very repair-friendly The solar panel assembly simply plugs into the unit’s main body with a standard barrel connector, so it is easy enough to unplug it and measure the juice coming from it. Even in dim, grey weather, I was still getting a healthy 11V (plus change) from the panel, so obviously that wasn’t the problem. I was surprised to see so much output from the smallish panels, even in low-light conditions. There was not much else that could be at fault, so it was time to demount the units, open them up and check the batteries. Getting them down is the first problem. Weather, especially with the extremes we have here, does weird things to screws and plastic, so taking all that off was a bit of a mission. I think I need to invest in better-quality screws! There’s not much I can do about the plastic breaking down, but even the cadmium-plated big-box-store superscrews I’d used had corroded and most of them just sheared off as I was trying to undo them. The ones screwed into the telegraph pole all broke off at the holes, so perhaps whatever they treated the pole with to stop it from rotting had a detrimental effect on the screws; they seemed especially weak. Once off, I got the units into my workshop. As you can imagine, they are a little grubby. Birds tend to sit on them and, well, you know. But at least the units came apart easily once I’d given them a wipe-down on the outside. Mostly, they are pretty well made. I doubt they are designed to withstand our summer sun, but the plastics seem to have stood up well. All the screws holding things together have little O-rings on them; another nice touch. The covers have a recessed O-ring as well, I guess just to keep the worst of the weather out of them. That’s a question for the techies: is a square seal still an O-ring? The things we think about! Once open, I could see that light number one hosts our 98 Silicon Chip The problem I had now was how to replace them. As usual, they are all spot welded together using nickel links with perma-soldered connections to the PCB. Finding replacement batteries shouldn’t be too hard, but finding them with solderable tags on them is a whole other story. I have one of those cheap spot-welders purchased from the usual Chinese sites, but it seems to kill batteries; not the batteries I’m trying to weld, but the model car/aeroplane-­ type battery packs that power it. I’ve had two high-­capacity batteries for it now, and they’re not as cheap as they used to be (nothing is!). Both failed internally after only a few uses of this welder. It must suck a tremendous amount of power out of the battery, but either the batteries are just poorly made, or the welder itself has some huge back-EMF that kills the cells or fries some fuse. I’m not about to pour more money down the drain buying expensive high-capacity batteries in an effort to get that working. There are far better options, but as I don’t do much of this work, it would end up like the treadmill still taking up space in my garage – used for a while, then forgotten about or pulled out once in a blue moon to be utilised. I did manage to find some 18650 cells with solder lugs; they’d have to do, and that got light number one back up and running. Light number two with the bigger batteries was a little more work. While I could find cells, I couldn’t find any readily available with solder lugs, so I had to use my soldering station. That is not ideal because adding that kind of heat is detrimental to this type of battery. However, I rubbed the contacts clean with a diamond file just before I soldered them and used flux, so the solder flowed well onto the joints. By spreading out the soldering process, I didn’t get too much heat into them. That light is now working again as well. Light number three, the mains-powered one, the most expensive and brightest by a wide margin, is 18 months old now. Obviously, it is out of warranty (darn it), and while it triggers, it is almost like a camera flash. It will not lux adjust or stay on. I took it down and opened it up, but the electronics are potted, and there is nothing to see there, so for this one, the only option is replacement, and that bites. The LED arrays and the rest of it, while very well-built and durable, are all just junk now because the brain is dead. While it cost more than the others, it is still not really worth digging into that much before it becomes one Australia's electronics magazine siliconchip.com.au of those jobs that are just too complex to solve rather than just buying another one. Yet another instance of built-in obsolescence... At least I got the other two back up to par (heh) and can now see where I’m going at five o’clock of an evening. And, as an added bonus, anyone coming up the driveway will be flooded with light, which is good for good guys and bad for bad guys (of which we know there are a few around). Vintage radios and the modified Crosley set I have held a ham license for around 65 years. When I got my license, the exams were only held twice a year, in February and August. They consisted of a 2½-hour paper on theory, half an hour on regulations, and the demonstration of 10 words per minute Morse code transmission. In many cases, the exams were held in the local post office as the Post Master who oversaw the exams was usually quite proficient in Morse code since telegrams were sent and received by Morse, and sometimes he had to fill in for other staff off sick or on holidays. Naturally, I grew up with all-valve equipment. The first transistor I purchased was an OC70, a germanium transistor that cost me nearly half my weekly wage as an apprentice: 4 pounds, 8 shillings and 6 pence, around $9.00. I have been involved in repairing and modifying a large number of old valve radios for many years. I lived for each month when Radio & Hobbies, then Radio, Television & Hobbies and finally Electronics Australia came out. Many hours were spent poring over circuits for transmitters, receivers, amplifiers etc. I have built up an extensive collection of valves of all types, as well as capacitors and resistors from the valve era. I always try to make the repairs look as original as possible. To that end, I found that I could carefully split old mica capacitors in half using a small hand-held grinder. I can then make a pocket inside the shells, insert a modern greencap or polyester capacitor of the required value inside, then cement the shell back together. For the paper capacitors, I cut off the lead on one end and carefully drill out the insides, replacing it with a modern one and then closing the end with beeswax. This results in a very original-looking unit. Unfortunately, replacement power transformers for valve radios are becoming very hard to obtain. I have endeavoured to use my metal lathe to wind new windings and resurrect some, but it becomes impossible unless I know the turn ratios. One of my pet hates is the American transformerless radio chassis. For some reason (probably cost-cutting), many US-made radios do not have power transformers. They use valves with the heaters in series, quite often with 17V, 25V, or 50V heaters to make the heater chain add up to the 110V AC mains. These valves also frequently have low plate voltages, although some radios use voltage-­doubling circuits to get a higher plate voltage. These radios are deadly. They rely on the operator inserting the power plug into the GPO the correct way around. However, because many power leads only have two pins on the plug, it is very easy to make the chassis live. Most of these radios don’t have an Earth wire because it would blow a fuse if plugged in the wrong way around! siliconchip.com.au 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. Besides using a variac when servicing these radios, I always use an isolating transformer to ensure my safety. There were some really well-made US radios, usually of the TRF type, before superhet radios became common. I had a lady bring in a Crosley radio one morning complaining that it had “blown up”. It was a five-valve transformerless superhet with several strange valve numbers because of the series heater chain. Further questioning resulted in her telling me that they had owned the radio for many years and it was a wedding gift from her husband’s father when they lived in the USA. It apparently had been “modified” by a radio tech in the USA before they came to Australia to suit the higher Australian mains power voltage. I put the radio on the workbench and tried to find the so-called modification she had claimed was done. Everything looked OK, but further checks showed that most of the valve heaters were open-circuit. She said that the radio had worked for years in their old house, but when they moved into the retirement village, the power lead was far too long, so her husband cut about two metres off it and reinstalled the plug. Australia's electronics magazine September 2024  99 I must be getting old because it took me fully five minutes to realise that the power lead he had cut was a ‘resistance’ lead that dropped the 230-240V AC in Australia to the 110-120V AC that’s common in the USA! Unfortunately, the radio was beyond economical repair due to the high applied voltage. I am currently working on a timber-cased STC 528 that has seen better days. It is working again, but it is still very deaf. Still, it keeps me out of the pub and busy at 80 years of age. J. A., Narangba, Qld. hearing was like that caused by a rubbing voice coil in the woofer. It was slightly gritty, but the speaker was still capable of going loud. I took the grille off the woofer so I could push the cone to see if it was rubbing. It felt fine, so I proceeded to remove the amplifier module. Probing the woofer output with an oscilloscope while playing music didn’t immediately reveal anything. The waveforms looked musical and were swinging nicely in both directions. However, when I fed in a sinewave, I could see the waveform wasn’t quite as smooth as the input. I disconnected the speakers so I didn’t have to listen to the tone and proceeded to trace the signal through the circuit. The output of the preamp looked fine. From there, it went into a voltage-controlled op amp used as a limiter (to protect the speaker drivers). The output of this stage is where the distortion appeared. This part of the circuit has only the op amp and four resistors; the control voltage comes from another op amp that rectifies the audio signals from both the woofer and the tweeter. The rectifier stage is fed with different amounts of signal from each driver so it can limit the signal at different levels, depending on whether the overload is HF or LF. I could see with the ‘scope that the rectifier stage was doing what it should. All this suggested the limiter op amp (BA6110) IC was faulty, but I didn’t have any on hand, and they are now obsolete. To prove my theory, I removed the op amp and linked between its input and output to see what happened. The result was nice clean audio, just a bit low in level. Then I remembered I had one of these amp modules in the ‘graveyard’. Ten minutes later, I had the BA6110 out of the donor and into the customer’s amplifier, but the fault was still there! A closer look at the circuit diagram revealed a 47kW resistor from the +15V rail to a pin on the BA6110 labelled “bias”. It measured as an open circuit. A replacement resistor restored proper operation. Several weeks later, the customer delivered another identical speaker, this time with no HF output. Some HF output was apparent when I tested it, but not much. Testing the amplifier module indicated that all was well, so I removed the horn driver for inspection. This revealed that the diaphragm had shattered! The voice coil was intact, but not much was left of the diaphragm. A new horn driver had it sounding good again. P. M., Christchurch, New Zealand. Another tale of two speakers Simpson washing machine solenoid repair A customer dropped off a powered PA speaker for repair, saying it sounded distorted. I played some music through it, and indeed, it did sound distorted. Problems like this present a quandary to me, as I am unsure whether to inspect the amplifier module or to start with the speaker drivers. Many modern, powered speakers have Class-D amplifiers that can deliver hundreds of watts. It is not uncommon to see labels on the speaker grille claiming 2000W, which is usually (!) a peak value. However, if the RMS value is only a quarter of that, it will still need very substantial drivers to handle the power. [I think you can drop a zero to get closer to the RMS power rating from these inflated figures – Editor] This particular speaker is an older model with conventional amplifiers and solid drivers. The distortion I was I refurbished a Simpson Contessa washing machine about two years ago and wrote it up for the October 2022 Serviceman’s Log (page 80). It had been working well until recently, when my wife found that it was not spin-drying the clothes but just bunching them up in one place and then going out of balance... I suspected the spin solenoid was at fault. If that was the case, it could be a problem, as I don’t have any spares left now, having used several over time for repairs to various washing machines. This particular component has a higher failure rate than others for some reason. I started by removing the machine’s lid to access the lid switch so I could hold it in while I turned the machine on in the spin cycle. Sure enough, the agitator started turning, and the familiar clunk of the solenoid was not present. The horn driver from a PA speaker with a shattered diaphragm. The Simpson washing machine solenoid had one of its terminals break off. 100 Silicon Chip Australia's electronics magazine siliconchip.com.au I disconnected the machine and pulled it out so that I could access the back panel and remove the seven screws that hold it on. I then turned the machine on its side to access the spin solenoid underneath it. One of the terminals had broken off, but the solenoid’s core was still moving freely, and there was no sign of overheating. That was a good sign, as it meant I could probably repair it. I removed the two #3 Philips screws holding the solenoid on and turned the solenoid on the elliptical pin to remove it from the machine. Next, I got my multimeter and checked that the wiring was still intact; it was. Another good sign. I plugged in my 20W soldering iron and, while it was heating up, got a pair of long-nosed pliers and a scraper to clean the broken terminal where I would be soldering it back together. I tinned both parts of the broken terminal and, holding the loose piece with the long-nosed pliers, I applied heat and soldered the piece back onto the solenoid. After cleaning the terminals, I checked the solenoid again with my multimeter, and it was all good. The repair might not look as good as new, but it would get the machine working again. I refitted the solenoid in the machine, reattached the back panel and stood the machine back up again. I refitted the lid, grabbed some wet washing, loaded the machine, set it on the spin cycle and pulled up the timer knob. The familiar clunk was present and, after the pump ran for a short time, the machine started spinning and ran for a few minutes before stopping. I checked the clothes, and they were as dry as usual, so the machine was back in action. My wife was happy to have the machine working again, and the repair cost nothing but a bit of time. These solenoids are not readily available and cost around $50 or more, so repairing the old solenoid at no cost was a win. It’s very handy being able to do our own repairs; it saves a fortune in call-out fees, and the old Simpson lives on. B. P., Dundathu, Qld Seismograph coil repair My seismograph stopped responding some time ago and I finally got around to fixing it. The detector coil is 50,000 turns of 0.1mm diameter enamelled wire, about 50mm in diameter. It had gone open circuit, not at the connections but internally. Still, it lasted about 40 years! I remembered the story of a bloke who had an open-­ circuit coil in a radio IF stage. He connected a 500V bridge megger to the ends, wound the crank fairly briskly, and it reconnected the coil. How? Electrostatic attraction? Punching through a corroded spot? Who knows, but it worked. The sensing coil carries almost no current, less than microamps, and is in a strong magnetic field, so how long would such a repair last? I don’t know, but for some time now, I’ve been thinking of upgrading the detector to a lightbased one that will also provide a DC resting graph. The magnetic one only responds to definite movement, whereas the commercial ones respond to very low-­ frequency, almost DC movement. Anyway, after doing that, it is working again, ready to detect quakes anywhere in the world. It is really that sensitive. I feed its output and that of the electrometer into two channels of a four-channel data logger connected to a small notebook PC. P. L., Tabulam, NSW. SC siliconchip.com.au Australia's electronics magazine September 2024  101