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SERVICEMAN'S LOG Odd happenings in my new house You never know what problems are going to crop up when you move into an old house and start renovating. In my case, we encountered some decidedly dilapidated electrical wiring but after tidying it up, we were hit with a puzzling power outage. I reckon that the house we’ve just moved into is cursed in some way. Weird things have been happening from the day we started renovations but there’s no evidence of an old crone ever living here and I’m reasonably sure that the house isn’t built over an old burial ground. So perhaps all the odd things that have happened can be put down to plain old bad luck or to my seemingly ever-present companion, Murphy. The first “peculiar” event concerned our mains power. During the course of our renovations, we had the walls and ceilings stripped naked and so had a golden opportunity to check out the wiring, much of which was showing its age. The main part of the house went up 1966 and it was mainly this area that we were renovating. This meant that we were dealing with the original 60s-era building materials and wiring. In one case, I had removed a light fitting from the ceiling and after undoing all the screws and pulling it down, much of the exposed insulation on the wires fell away in small, brittle fragments. This left about 40mm of exposed copper wiring looking very dan- 40  Silicon Chip gerous and in obvious need of replacement. My reaction at the time was that if the rest of the wiring was anything like that, we were going to have some real problems. This section of the house was built just like most other houses in this country at the time. It was all quite basic, with no fancy extras such as under-floor, wall or ceiling insulation. And with typically only one notoriously inefficient open fireplace located in the family room to heat the whole house, residents were obviously expected to weather the savage Christchurch winters with nothing more than Dave Thompson* Items Covered This Month • • • • • Gremlins in Dave’s new house Bosch BSG82030AU/01 vacuum cleaner Sharp microwave oven repair Fuses can be deceptive Merlin Powerlift garage door opener grim fortitude and a pioneering spirit! During our renovations, we took the opportunity to rectify that situation by adding decent insulation and the difference it made was remarkable. Because the majority of the downstairs wiring was still original, it was replaced wherever it was possible to access it. To be honest, the wiring was a mess due to circuits being added over the years. Some circuits disappeared off with no apparent destination, or at least none that we could trace. There was also an outside light mounted on a faux Victorian lighting standard that was never used because the previous owners didn’t know where the switch was or even if it existed. We borrowed some nifty electronic tracking tools from a sparky friend that allowed us to map out the fuses and switchboard to the various power and lighting circuits around the house. In the process, we located several power feeds that didn’t go any­where at all, disappearing at various locations into the joinery and back out but not terminating in any outlets or switches. These were stripped out to avoid confusion. To accomplish this as safely as possible, we removed the pole fuse, which was a large ceramic-bodied, bayonetfitting fuse arrangement mounted (confusingly) on the edge of the roof. It connected the house wiring to the mains feed coming in from the street. According to my electrician friend, it was rated at 65A and was easily removed by turning it 90° anti-clockwise until it dropped free. With the pole fuse removed, the siliconchip.com.au house is theoretically isolated from the grid. Even so, I ran all my mains-detection devices over the switchboard before going anywhere near it, wary that some cowboy may have wired things up badly at some stage in the past and that this could catch out amateurs like myself. For those concerned readers, I can assure you that our friendly sparky – who but for very recent surgery would have been doing more of the physical work himself – oversaw every stage of the process. In fact, I ran everything by him (before and after) to make sure it was up to code and to ensure I wouldn’t be killed in the process! In the end, we examined all the wiring we could access and removed any that looked even slightly dodgy. In the process, we found one circuit in the 80s extension where four power sockets had been cabled in using wire intended for lighting circuits. We removed all of it right back to the switchboard and replaced it with new wiring with the correct specification. Most of the wire used by the original electricians was a flat, twin-core type with a plain copper earth wire buried down the middle of the insulation. Any­thing utilising this type of cable was replaced with modern triple-core flex with a separate (and properly-insulated) multi-strand earth wire. In addition, every socket and light switch was replaced with new, modern plates and switches and any sockets used in wet areas included inbuilt RCDs. Over the years, the switchboard had become a bit of a rat’s nest, with what seemed like a separate circuit and fuse for every individual socket and light switch. We ended up replacing two of the buss bars due to the old ones being full to the brim with wiring and because both also had several stripped connectors, meaning those particular holes could no longer be used. Because there was literally no room left in the switchboard, we had to cull some of the circuits and combine others where possible so that we could add some heavy-gauge cabling and breakers for new heat pumps and a new oven. As a final upgrade, we replaced the old ceramic and wire fuses with circuit breakers. This was a reasonably expensive job given the price of the circuit breakers but one well worth doing. In the end, we did a lot of electrical work and I thoroughly enjoyed doing it under my friend’s supervision, acquiring a few new skills and some good knowledge along the way. (Editor’s note: unlike Australians, New Zealanders are legally entitled to do house wiring but it must conform to AS/NZS 3000 standards and must be inspected and signed off by a licensed electrician). While the floors were up in various places, we decided to overhaul the plumbing system by replacing all the rusting old galvanised water pipes we had access to with butylene equivalents. However, this impacted on our electrical system because many older homes utilise the metal plumbing structures for mains earth purposes. This means that removing old metal pipework can leave the house in a potentially dangerous state. To rectify this, my sparky overseer stated that as we didn’t appear to have a dedicated earth point for the house, we had to add one. To this end, we sourced the required 2-metre-long earth rod from a local supplier and drove it the regulation 1.8 metres into the ground right beside the house. After attaching a new earth cable to it (and the mandatory plastic tags warning about removing it), the wire was run through the house’s framework and terminated at tel: 08 8240 2244 Standard and modified diecast aluminium, metal and plastic enclosures www.hammondmfg.com siliconchip.com.au November 2016  41 Serr v ice Se ceman’s man’s Log – continued The Vacuum Cleaner With No Suck A vacuum cleaner that doesn’t suck sucks. S. G. of Brookvale, NSW got this one sucking again . . . Lesley’s vacuum cleaner, an 8-year old Bosch BSG82030AU/01 unit with variable suction control, was sucking up the dust quite nicely one day when suddenly its “suck” disappeared. It was so sick that it could hardly vacuum up fluff from a tiled floor, while on carpet it was completely useless. The first thing Lesley did was poke a flexible hose through the wand assembly and the floor nozzle to clear any possible obstructions. They proved to be clear, so Lesley replaced both the collection bag and the motor protection filter that sits behind this bag, in front of the motor intake. The socalled “HEPA” filter that sits in the exhaust outlet was also inspected but it appeared to be clean and was left in place (HEPA is an acronym for “high efficiency particulate arrestance”, in case you’re wondering). The collection bag and motor protection filter replacements failed to cure the problem and so, after inspecting the hose/wand assembly for damage, Lesley threw her non-sucking vacuum cleaner into her car and took it to an appliance repair centre. When she collected it several days later, they told her that the problem had been fixed by installing a new HEPA filter and billed her accordingly. Well guess what; the new HEPA filter made no difference although in fairness to the service centre, it was easy to be misled as the machine appeared to have reasonable suction at the hose connection socket. At that point, I offered to take a look at it and Lesley demonstrated the fault to me before handing the machine over. During this process, we discovered that the motor speed could be varied only up to about half-way. Moving the suction control over the top half of the range had no further effect, the motor speed remaining constant. My initial thoughts were that if the motor speed could be varied over the first half of its range, then there probably wasn’t much, if anything, wrong with the motor control module. Perhaps it was nothing more than a faulty pot on the the switchboard’s ground bus. The thing is, without a professional electrician guiding me, I likely wouldn’t have even considered the ramifications of changing the plumbing. And that’s precisely why DIY/cowboy electricians and plumbers can be so darned dangerous. Electrical and plumbing work should both be left to those who know what they are doing! As another example, during the quakes we dealt with so many prolonged power outages that a lot of residents purchased petrol-driven generators to keep their essentials running (myself included). However, I heard of several instances of people receiving severe electric shocks due to near neighbours connecting generators to their household supply and thus to 42  Silicon Chip control module or a simple mechanical fault in the speed control mechanism? Google to the rescue Now I’m no vacuum cleaner repairman, so the first problem was to figure out how to remove the top cover from the rear half of the unit, so that I could get at the speed control assembly and motor control board. Lifting up the cover above the dust collection bag revealed two self-tapping screws that clearly had to be removed, while another two were hidden deep down in wells under the HEPA filter cover. However, even with all four screws undone (and the collection bag and filters removed), the top cover stubbornly refused to budge. I searched for extra screws on top but there were none, so I looked at the base of the unit. There were no screws visible there either, so were they hidden under the steerable wheels and if so, how did the wheels come off? That’s where Google came to my rescue. A quick search on dismantling this unit revealed that you have to prise off the two rear wheels using a flat-blade screwdriver. This then reveals plastic clips on either side of the unit and releasing these allows the top cover of the machine to be lifted clear (after pulling the power cord part way out). With the top cover out of the way, I took a look at the speed control drive mechanism. This is nothing more than a plastic spindle with a curved blade which runs between the two fingers of a Nylon slider bracket. As this bracket is slid one way or the other along its mounting rail, the spindle rotates and drives a potentiometer on the control board. Basically, it’s a very simple gear mechanism that converts a linear control action into a rotary control action to drive the pot. As it turned out, the problem was the grid because an isolating switch wasn’t used. In the process, they inadvertently “livened up” neighbouring properties where the householder had assumed the power was off-line. A few discovered that their wiring was in fact live the wrong way and it’s indeed fortunate that no-one was killed. I’ll now get to the main point of this siliconchip.com.au The speed control (left) rotates a curved spindle which in turn rotates a pot on the motor control PCB. The photo at right shows the partly-cleaned intake blades. staring me right in the face – the Nylon slider bracket had somehow become detached from the curved blade on the spindle. All I had to do to re-engage it was slide the Nylon bracket off its rail at the low-speed end, then slide it back on again with the spindle’s blade positioned between the bracket’s fingers. Once it was on, I applied power and gingerly varied the slide control, all the time taking great care to keep my hands well clear of the control board which operates at mains potential. And that was it – the motor speed could now be varied right across the control range and the motor could now be run at its top speed. Job done, I thought, so I reassembled the machine, gave it a quick test and returned it to its owner. My triumph turned out to be shortlived. Lesley subsequently reported that although the machine was now working reasonably well, it still wasn’t performing at its full potential. Apparently, at the maximum setting, it should suck an elephant through the nozzle (OK, a slight exaggeration) but it was still nowhere near capable of doing that. And so I faced up to Lesley’s baulky Bosch for round two. I began by carefully examining the hose and wand assembly, looking for blockages and air leaks. This revealed nothing, so I dismantled and cleaned the floor nozzle but again found nothing that would cause loss of suction. The suction control was still correctly varying the motor speed over its full range, so that indicated that the control module itself was OK. It was beginning to look like there might be a blockage or a restriction near the motor somewhere. I dismantled the machine once more, unclipped the top cover from the motor housing and lifted the motor clear. Once again, the problem was staring me in the face; the intake blades at the front of the motor were badly covered with a build-up of hair, dust and fluff (see photo). It was so bad, it was a wonder that the machine ran as well as it did. Fairly obviously, this problem had been building up for some time but because the loss of performance had been gradual, it largely went unnoticed until the speed control mechanism went haywire. I removed the fluff from the intake blades using a flat-blade screwdriver and a soft brush, then used my own vacuum cleaner to suck out any remaining debris. The reassembled machine then really did have lots of “suck” and has many years of life left in it yet. story (it’s been a long time coming, I admit). Anyway, half-way through the renovation process, we’d plugged the pole fuse back in so that we could test some of the lights and switches we’d installed. However, while we were checking things out, the power suddenly went off. This was rather odd as we weren’t really doing anything at the time. And while we still had some un-terminated live cables hanging out of the walls, everything was well-insulated with tape, so I was reasonably certain that we hadn’t caused the outage. We initially went outside and check­ ed the pole fuse, half expecting it to be fried, but it was intact. A quick check with a neighbour then confirmed that there wasn’t a general power outage, so Round 2 siliconchip.com.au there was definitely something wrong with our mains supply. All we had to do was find out what the problem was. Over the previous few days, we’d been installing LED lights in the kitchen, laundry and bathroom and I’d noticed that they sometimes flickered when they were on. At the time, I thought that this was probably due to the fact that we still had a lot of connections to tidy up in the switchbox and my electrician friend agreed with this, as some connections can loosen with age, As it turned out, a lot of the connections on the switchboard fuseholders required at least two screw turns to fully tighten them. Unfortunately, although this reduced the flickering somewhat, it still remained right up until the power completely failed. Tracking it down With full access to a range of electrician’s tools and gadgets, I was confident we’d be able to quickly track down the cause. I began by climbing back up the ladder to the pole fuse. We’d been mucking around with this, so it was a natural place to start. My contact-less mains detector showed power flowing in from the street and up to where it entered the ceramic pole fuse housing. From that point on though, I was unable to detect anything, so it had to be the fuse, didn’t it? I removed the fuse and had a good look at it under a magnifying lamp. Its contacts, though aged and a bit corroded here and there, appeared fine and the fuse checked out OK on my multimeter. I then used my diamond contact shaping file and some fine-grit sandpaper to clean up both the holder and the fuse contacts but this made no difference; we still had no power. Next, I took a closer look at the mains feed where it entered the fuseholder and discovered that the insulation had bubbled and discoloured – obvious signs of overheating. This could certainly have something to do with the problem but I wasn’t going there. I’d made (and was obeying) a self-imposed rule of touching nothing on the incoming side of the pole fuse and in any case, I wasn’t authorised to do so. Nor did I have the knowledge or the courage to muck around with a live mains feed. My sparky mate confirmed that we’d have to get hold of the power company to go any further and they had a guy out November 2016  43 Serr v ice Se ceman’s man’s Log – continued to my house within a couple of hours. I was straight up with him about what we’d been doing and accepted that if the fault was down to me, I would be up for the cost of the repairs (the standard operating practice for most utility companies). As expected, the linesman had all the right tools; a proper wooden extension ladder, a heavy-duty safety apron and rubberised gauntlets (or long gloves). After listening to my theory about the dodgy-looking feed wire, he checked the meter box before climbing up to the pole fuse. He did what I’d done to test it, with the same result, and agreed that the signs of overheating were a concern. And then, as soon he touched the wire, it dropped clear of the pole fuse. “There’s your problem,” he commented dryly! On closer inspection, it had corroded through, probably over many years, heating up as each strand gave way and less wire carried more current until it picked this moment to finally let go. His initial plan was to simply re­ attach the cable to the pole fuse, tidy it up and carry on but one of the two brass screws that fastened the cable into the ceramic holder sheared off as he tried to release the burned-off end. This triggered a chain of events that entailed a new pole fuse being installed and even a whole new pole! The reason for this is that new pole fuses need to be mounted at a certain height but our old pole was too short to comply. That meant that a new one had to be installed. In the end, it was a different and a much more modern arrangement. Best of all it finally restored power to the house so we could carry on with our renovations. Sharp microwave oven repair Microwave ovens are now so cheap that most people immediately replace a faulty unit with a new one. Not so J. N. of Tauranga, NZ. When the display on his microwave oven failed, he fixed it instead of consigning it to landfill . . . We’ve owned a Sharp Carousel microwave oven for some time now and it has suited our purposes admirably. Unfortunately, its display suddenly disappeared one day but all the other functions were still fine. As a semi-retired electrical/electronics technician, I like to do any repairs on our home appliances myself and this Sharp microwave was no exception. I began my investigation by dismantling its front panel and found a single PCB mounted behind the display. I then downloaded the matching circuit diagram from Sharp’s website. It didn’t take me long to realise that the combined display/processor IC had simply given up powering the display. I then contacted a Sharp parts supplier but they couldn’t supply the PCB alone, instead quoting for a complete front panel and PCB for NZ$199 + GST. I declined; for that sort of money, I could buy a new microwave! I was not about to give up that easily, however. I had the Sharp part number for just the PCB, so I surfed the net for a replacement. Amazingly, I came across the exact replacement on eBay, complete with the front panel, for an outlay of just NZ$49 landed in NZ. When it arrived, I swapped over the power supply transformer from our old unit in keeping with our 230VAC mains input, since the US transformer it came with was for 120VAC. After reassembly, the microwave worked perfectly again and I was feeling very pleased with myself until I realised that the clock was running at the wrong speed. This also meant that the timer would be way out. And then the penny dropped! After checking the circuit diagram, I realised that the oscillator running the proces- Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column? If so, why not send those stories in to us? We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. 44  Silicon Chip sor was locked to the mains frequency and this new unit needed 60Hz instead 50Hz to operate correctly. Determined not to be beaten, I isolated the now 50Hz pulse to the processor at its INTPO terminal. I then delved into my spare parts box where I was lucky enough to find an MM5369 oscillator IC and a 3.579MHz crystal. Armed with these parts, plus a few passive components, I then constructed a pulse unit on Veroboard which produced a nice 60Hz output. The next step was to “steal” some power from the processor’s DC supply to power this add-on board. The output from the MM5369 was then connected to the processor’s INTPO terminal and the board secured in position. The timebase conversion proved to be a success and our old Sharp microwave is still soldiering on, with a nice clear display. Fuses can be deceptive There’s only one sure way to check a fuse and that’s with a meter, as L. W. of Logan, Qld found out when he tackled a faulty AC/DC fridge. Here’s what happened . . . On our new caravan’s maiden voyage, I noticed that the 3-way fridge didn’t seem to hold up too well when operating on the 12V setting. It worked fine on either 230VAC or the gas setting but seemed to defrost rather quickly when 12V operation was selected. For those unfamiliar with these devices, 12V operation is intended to only keep an already cold fridge cool; it definitely does not have the capacity to chill from scratch. As a result, this setting is usually only selected while in transit, when 230VAC is obviously not available (unless using an inverter) and running off gas is not recommended for safety reasons. The 12V supply is usually provided by the towing vehicle’s battery and should be set up so that it powers the fridge only while the vehicle’s battery is being charged from the alternator. Nominal heater resistance is in the vicinity of 1Ω, so a battery voltage of 12.5V at the fridge results in a current of 12.5A and this would flatten the battery in a short time if it wasn’t being recharged. We made several trips during which the fridge quickly defrosted (ie, when powered from 12V) before I finally decided that something had to be done. After some thought, I decided to have siliconchip.com.au Merlin Powerlift Garage Door Opener Remote-controlled garage door openers are great except when they don’t work. The electronic gremlins recently got into a controller belonging to A. D. of Naremburn, NSW while he was overseas but he managed to evict them and get it working again . . . Many years ago, I built a garage from a kit and fitted a power-operated Merlin Powerlift roller door opener. It was quite easy to fit and it was subsequently used for many years without problems. Several months ago, I went overseas and, following my usual practice, I disconnected the power to the door-opening mechanism before leaving. However, when I subsequently returned after a couple of months and plugged it in again, the remote control wouldn’t open the door. I tried the manual button on the controller housing and it worked fine but it stubbornly refused to work with the remote transmitter. I rang the company that I purchased the unit from and explained my problem. She quickly told me that it was probably the remote control itself and informed me that she a look at it myself rather than take the caravan to the dealer. The installation manual conveniently provided a wiring diagram and it showed that the circuit was quite simple: a heating element in series with a 25A fuse, in turn connected through the mode switch to the 12V supply. So how hard could it be? The first hurdle came when I removed the outside vent covers to access the rear of the fridge. Only the 12V connection point and one end of the heater wiring were visible; there was no fuse to be seen. This meant that I couldn’t test the heater element or the fuse independently for continuity. At that point, I connected my voltmeter across the 12V connections and, with the towing vehicle connected and its engine running, measured a healthy 14V with the fridge switched to the off position. Switching the fridge to 12V operation had no effect on this voltage reading, so I then decided to check the current. Just as I suspected, this gave a reading of 0A, indicating that there siliconchip.com.au could sell me a replacement. When I suggested that it may not be that and asked what I should do if it still didn’t work, she had no reply other than to suggest buying another complete unit at a cost of $770. Unfortunately, she wasn’t able to provide any schematics and so I found a company which sold and repaired such doors. The guy I spoke to told me it was so old they didn’t have spares but he’d check it out for $282, which included the price of another main electronic unit. Since I had paid only $375 for the whole thing originally, I didn’t think that was worthwhile and thought that a simple solution would be to wire a remote switch (as sold by Oatley Electronics) across the manual button contacts, thereby completely bypassing the original remote control circuitry. In fact, I use just such an Oatley remote switch to control my home-made gate opener and I figured that I could use a spare button on the existing gate transmitter to trigger the garage door controller. Before doing this though, I decided to have a look at the garage controller and its remote to see if I could was an open circuit somewhere. There was nothing for it; the fridge would have to be completely removed in order to gain better access to its rear. An hour later and with the back of the fridge now exposed, there was still no sign of a fuse. The problem was that both the 230VAC and the 12V DC wiring from the heaters disappeared under a thin metal cover which covered most of the top of the fridge. Fortunately, this was easily removed by undoing four screws and at last there were two fuses visible. I was also able to see where the 12V heater element connected to its fuse and switch assembly. Being a 25A fuse, it was easy to “see” that it hadn’t blown, so I decided to check the heater element for continuity. It measured just under 1Ω on the multimeter, which is normal. I was getting a bit frustrated by now because that left only the switch as a suspect. And as it was a multi-pole switch that contained four sets of contacts, I really didn’t fancy dismantling it to find out what the trouble was. find the fault. The LED on the remote still came on when the button was pressed, so I looked at the controller itself. On examining the main PCB, the first thing I noticed was a blackened resistor and a small 3-terminal device which appeared to have overheated. Fortunately, I could just read some of the writing on it and it appeared to be a 6V regulator. One of the legs on this device was burnt where it entered the PCB and the track had been damaged. I didn’t have a 6V regulator but I did have a 5V regulator in my parts drawer, so I wired in some resistors in the usual fashion to increase its output voltage, replaced the faulty resistor and repaired the damaged PCB track using some tinned copper wire and solder. That was it; as soon as I reassembled it and applied power, I was rewarded with a perfectly working garage door opener again. I have no idea what caused the original regulator to blow, since I had disconnected the mains supply from the controller before I went away. However, judging by the burnt tracks, it was obviously something fairly drastic and it almost certainly occurred when the unit was powered up on my return. It was then that I recalled some advice that I was taught way back during my training days: “always test a fuse with your meter. It may look OK but you won’t know for sure unless you see that needle move over to read zero ohms” (no digital meters in those days). And so, with no better ideas at this stage, I removed the fuse and tested it on the low ohms scale of the multimeter. It measured open circuit! I tested it several more times because I just couldn’t believe what the meter was saying. After all, it was a 25A fuse and it appeared to be intact. Replacing this fuse restored the fridge to 12V operation for the first time in its life. All that was left then was to replace the metal cover and reinstall the fridge in its cabinet. Several days later, I hit the ends of the faulty fuse with a hot soldering iron and as one end was heating up, its metal cap moved very slightly inwards. From then on, it read OK on the meter and so, just as I suspected, it had been SC faulty from new. November 2016  45