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SERVICEMAN'S LOG ‘Playing’ with fire Dave Thompson I always hesitate to ‘help’ repairers or installers do work in my home. While I presume that my talents would come in handy (even if I’m just acting as a third hand), I know how frustrating it can be when someone who is not an expert is hovering over you. Sometimes, a ‘helper’ is actually a hindrance. In this case, I think the guy appreciated assistance from someone with decent electronics knowledge. A little while ago, I was sitting in my workshop doing somethingor-other when suddenly there was a huge boom! The earth shook, dust fell from the light fittings, and everything on the bench was rearranged slightly. This didn’t overly disturb me, as earthquakes are a dime a dozen here these days. I’ll admit that my heart did race a little, as it always does with quakes, though I did think it a bit unusual at the time. Most ‘quakes don’t have the sharp shock and loud audio soundtrack this one had, tending instead to be rolling, rumbling affairs lasting perhaps 30 seconds or more. This one was very short and sharp, and quite loud, but I thought nothing more of it at the time. I know, great story, right? However, this will all become relevant later, I promise! Keeping the ‘cave’ comfortable Increasingly, our news reports seem to be chock full of extreme weather events. If it isn’t droughts, it’s floods, and if it isn’t wildfires, it is plunging temperatures from seemingly endless polar blasts. Sometimes both of these will happen in the same place, just a few months apart. While being so far away from the hottest places on the planet does help us here in New Zealand a little, being so close to very cold places does have its drawbacks. Anyone who has visited Christchurch (or anywhere further south of here) in the middle of winter will know what I’m talking about. This year, we have record-breaking ‘cold snaps’, which sound vaguely appealing, like something my grandma siliconchip.com.au would have baked. But to those of us living here, they are anything but. When the mercury drops to -7°C of a morning, for example, one really appreciates having a well-insulated, well-heated double-glazed home. The rub is that most homes built here before, say, the 1980s are mainly uninsulated (apart from some having fibreglass insulating batts retrofitted into the roof over the living areas if you were posh). They typically have single-glazed windows, making them increasingly inappropriate for the temperature extremes we are now seeing in the summer and winter months. My parents’ ex-home, which we have just sold due to them not being here any longer, is a classic example. Mum and dad added insulation and better windows to their 1959-built house, where practical, while they lived there. But with no wall insulation, minimal roof insulation and originally just two back-to-back fireplaces to heat the whole house (eventually replaced with stand-alone electric heaters, then heat pumps), the home was very susceptible to heat and cold. It was sweltering in the summer and impossible to warm up in the winter. These days, it is increasingly important that houses be properly built and well-insulated. Not only is it a nicer place to be, but it is also a lot less expensive to heat or cool, especially given that costs of energy – whether electricity, gas or wood – are all going through the roof (pun intended!). Time for an upgrade Recently, the 35-plus-year-old Australia’s electronics magazine Items Covered This Month • ‘Playing’ with fire • TV remote control repair • Surround sound system repair • RS-485 network with • • intermittent faults Philips AE5230 radio repair Repairing two laptops that wouldn’t POST *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Masport LPG gas fire we inherited when we bought this house five years ago started playing up. The Masport range is well-known and seems to include pretty decent products. However, the model in our lounge was deprecated years ago and finding information on it turned out to be a challenge. The ‘modern’ Masport company has nothing relating to it on their website, not even giving it a listing in its ‘old bangers’ section. I eventually found, through a helpful forum post, a PDF service manual for it. With that, I could finally plumb the depths of what is still available for it parts-wise, which, as you can probably guess, is 5/8ths of less than nothing. So, the weather was getting colder, and our gas fire often wouldn’t start properly (which entails opening a valve to the ‘light’ position and pushing a piezo striker button repeatedly until it decides to work). When it did light, it performed poorly. September 2021  75 When we first moved in, one push would ignite it, and the valve was infinitely adjustable (according to the equally-spaced markings painted on the top of the dial) from a tiny flame to a roaring fire. It suited us perfectly, especially after moving from a pellet stove/fire in our old house which, while efficient and easy to manage, entailed lugging 20kg bags of wood pellets around. That increasingly became a downside for me over time [people pay good money to gyms so they can get exercise like that! – Editor]. However, lately, the fire’s gas valve had to be set to full before the fire would even start, and even then, we often gave up because it just wouldn’t go at all. With research (as is the serviceman’s way), I found the valve’s manufacturer, as that is where I suspected the problem lay. I then discovered that even if we could get one, it would cost around $600-700. I wasn’t keen on throwing too much money at this old fire, but probably would if it was likely to get it back into full working order. Calling in the experts In the end, I bit the bullet and called in a gas serviceman. I’d need a licensed gas guy regardless, and if nothing else, he could ensure our bottled LPG gas system (with two 45kg cylinders) was delivering the right amount of juice to the fire. We also have a gas cooking hob on the same line, and while that seemed OK, for troubleshooting purposes, one has to start somewhere... He had all manner of cool tools to do his work, especially the electronic stuff like digital manometers 76 Silicon Chip and differential pressure meters, all of which looked like something I could use! Now, I’m quite aware of people looking over my shoulder when I’m doing my thing, so I made sure to ask this guy if it was OK if I had a look at what he was doing and how he did it, purely out of professional interest. This wasn’t so I could try to do it myself in the future – working with gas is fraught with potentially lethal pitfalls for the amateur. And here I refer back to my opening statement; a few years ago, a house a couple of kilometres from here (as the crow flies) literally exploded because a gas fitting job wasn’t done properly, which created the colossal boom I’d heard and shook the ground. It was a miracle nobody was killed, but there were some serious injuries and a ton of collateral property damage, so I made a pact that I would never mess with such things. I merely wanted to look on and understand the system used in this house for myself. The guy did some typical pressure and flow tests and determined our bottle regulator, an ancient switchable gas valve that I thought could only be manually switched between bottles, was working but a bit iffy. For the relatively low cost of 150 kiwi bucks, it was well worth upgrading to a newer (and presumably more efficient) model. It also seamlessly auto-switches between bottles when one runs out, something the older one apparently should have done but never did, at least in my experience. That meant the old fire itself was the problem, and though he serviced it, it still sooted up and gave below-normal heat output. It was obvious we needed a new one. Australia’s electronics magazine The astute reader will realise there isn’t much electronics-related material in this column so far; here is where that all changes! It’s a gas, gas, gas Long story short (thank goodness!), we decided on a new gas fire. Though a different brand, the new version is essentially the same physical size but has a higher efficiency rating and overall heat output, so that’s a couple of boxes ticked already. It also bristles with electronics, and there is even an app and optional add-on that allows users to control it from anywhere with mobile phone coverage. I like it very much already! Another feature is the remote controller; this enables instant, singlebutton starting, fan speed control, on/off timer settings and even thermostatic control of the room temperature. A thermocouple that picks up the room temperature is clearly visible through a 1mm-round opening in the side of the remote controller. This is a double-edged sword, though; surely it would depend on where in the room the controller was sitting as to what temperature it picks up. The remote comes with a wall mount, which they recommend putting somewhere handy to the fire. However, common sense tells me that if I put it on the wall right behind the stove, it will be a lot warmer there than across the room, so it won’t have a good indication of the overall room temperature. I’ll have to think about this feature for a while... Installation was the next step for the serviceman. This also interested me, as it became evident as the process went on that I could have easily done this job, except for the ‘gas’ side of things, obviously. The practical side could be done by anyone reasonably competent with manual tools such as drills, concrete screws, wall plugs and the like. In fact, many of the fittings looked very similar to the hydraulic lines and fittings I would have used back in my airline days, and many of the flanging and sealing processes were very familiar. While I was reasonably confident I could have done all this, there was the nagging doubt that the house could explode if I messed it up, and I’m pretty sure the insurance assessor wouldn’t be overly impressed! Fair play! siliconchip.com.au I didn’t want that on my conscience anyway. Lending a helping hand (or 2) The serviceman who installed the fire was an older-school type, and while very adept at the mechanical side of the task, he seemed to be struggling a bit with the electrical/electronic side of things. It turns out he’d installed dozens of this type of fire, but none with the electronic modules fitted, and this obviously perturbed him a little. I offered to help where I could, and he was grateful, even naming me his ‘wingman’ in several telephone conversations he had with his colleagues. I doubted I’d be of much use, but helped out initially holding torches and keeping things steady in cases where a second pair of hands is most welcome. When it came to wiring it all up, I could see he was not that comfortable with the wiring diagrams and sparse instructions printed in the installation manual. The first problem I could see, and something I foresaw the day before as the guy was drilling holes in the concrete hearth for the fire mounting fasteners, was access to the electronics. While there is a manual ‘control panel’ in the bottom front of the unit, it isn’t very large. It appeared to me by reading through the manual that we’d eventually have to take the various electronic enclosures inside the fire out to work on them. With the fire bolted down, there was very limited room out back to remove this stuff. Surely, they could have printed the manual so that installers could do all this electronics-related work before the thing was installed. I suppose this is where experience comes in; the guy will know for next time, I guess. So mechanically, the fire was securely attached to the floor (a requirement now with quakes being what they are here), but we needed to tweak a few things before we could (ahem) fire it up. The first thing he had to do was convert the stove to run on bottled LPG gas rather than the natural (reticulated) gas it is initially configured for. That entails swapping several internal jets over with the supplied kit. It also had to be changed in the electronic controller, which by now was very difficult to get to. It just wouldn’t come out the siliconchip.com.au front, so we had to try to get it out via the back access panel. I eventually managed to finagle it out. After removing three screws, which doubled as cable clamps at one end of the industrial-looking plastic controller box, I could remove the top. Apparently, there was a ‘jumper’ in there that had to be set for LPG use, but the photos in the Xeroxed installation manual were woeful, making it very difficult to locate. As the installer guy admitted that he had never seen one and didn’t know what to look for, I volunteered for the job. With the usual holding of torches, twisting of bodies and lots of blue air, I finally found the jumper buried in the shadow of a heatsink of some semiconductor or other. Fortunately, it was identical to the typical computer motherboard or hard drive jumpers I’ve grown old with, so I recognised it as soon as I saw it. A set of curved long-nose pliers (supplied by me) enabled me to flip it around, and I set it on one pin only. I could have removed it altogether, but this allows any future owner (however unlikely that scenario is) to revert it to natural gas operation more easily. With the correct sticker applied to the lid of the enclosure (to show it had been converted for LPG use), I remounted the top, finding that in the meantime, all the cabling had expanded, so I needed longer screws. Once again, I went to my workshop to look in my parts bins; luckily, I have literally thousands of screws of all types saved over the years, and soon found three that were suitable. Once buttoned up, I could stuff the controller box back into the cavity. I tried to position it as far from anything hot as possible, and routed all the cabling into place as best I could, tying it back with cable ties (again supplied by me) where necessary. While the front panel was still open, the last thing was to put a digital manometer onto a tap by the main jet and adjust the low- and high-pressure settings for the flame. Then the acid test: with a single tap of the remote controller button, the electronic lighter crackled, and the fire lit up immediately. Flame up and down is just as smooth, and with thermostatic control, our gas usage should be much more manageable. What luxuries modern electronics give us! Australia’s electronics magazine Overall, I think the serviceman/ installer guy was pleased to have my help, but it is hard to know sometimes. We haven’t had the bill yet, so we’ll soon see how much he appreciated it! TV remote control repair B. P., of Dundathu, Qld came up with an unorthodox repair for a wornout TV remote control. You might not expect it to work, but it did, solving a common problem that plagues many old remotes... Several years ago, we picked up a 27-inch TCL TV at a charity shop. This fitted perfectly in our entertainment unit in the lounge room, replacing a more than 20-year-old CRT TV. This TV only has an analog tuner, but we were using it with a PVR that has a digital tuner anyway. The TV performed well for several years, but recently I noticed that it was getting hard to turn on. I had to hold down the power button on the remote hard for several seconds. This fault was at its worst during winter, so whatever was causing it was apparently temperature-sensitive. The remote control for the PVR has a mode where it can operate the TV, but it only provides limited controls. But at least it lets you switch the TV on and adjust the sound and picture. I tried this and found that the TV turned on straight away, so the fault was with the TCL remote control. I dismantled the TCL remote to diagnose it. Care needs to be taken when dismantling remote controls, as it’s quite common for the clips to break. In this case, though, it was quite easy to get it apart without any damage; I was able to use my thumbnail to prise the case apart. I inspected the circuit board and found it to be quite dirty from many years of use. I cleaned the circuit board and the rubber pad button contacts, and then I laid the rubber pads on the September 2021  77 circuit board and fitted the batteries to test it. Unfortunately, it still didn’t work correctly, suggesting that the conductive material on the pads had worn out. I decided to try putting some conductive grease on the pads to see if that would solve the issue. Being a retired motorcycle mechanic, I was fairly sure I would have some sort of conductive grease on hand, such as graphite grease or similar. I checked my workshop and found some copper-based grease, so I tried that. I smeared the circuit board contacts with that grease, then overlaid the rubber pad and worked the buttons to ensure that each button’s contact had a light covering of grease. After lightly wiping down both the circuit board and the pads, I reassembled the remote control and tested it. It was now as good as new, with just a light touch switching on the TV. Several months later, it’s still working well, so this was another successful fix using a simple solution. Surround sound system repair B. C., of Dungog, NSW is the type to help out friends by fixing their gear when it acts up. In this case, the receiver had already been ‘professionally’ repaired, but it still needed a lot of work to put right... It started as a simple request to reconnect all the surround speakers to Trevor’s LG DVD/VCR combo receiver (model LH-CX640W), a device with more accoutrements than your average house. Apparently, it had been repaired by a service centre in a larger town some time ago. After its return, it had only been reconnected to the television using an AV cable; the handful of speaker cables had been left unconnected at the back of the cabinet. When the cabinet was moved out away from the wall, a rat’s nest of very light gauge speaker cables was revealed. I decided to run all-new heavier gauge speaker cables and also to clip them up on to the floor joists (the old ones were dangling). The old cables were used as draw wires, and apart from two of the runs, there was enough crawl space to fit most of the cables without too much bother. I then connected all six speakers to the LG receiver and powered it up. Upon playing a DVD, the centre speaker and one rear speaker were silent. Tapping the top of the LG Combi Receiver would intermittently restore audio to these two channels. I disconnected everything again, took it to the kitchen table and removed the main PCB. I resoldered all the terminals on the speaker output block; some had obvious dry joints. After refitting the PCB, the machine was reconnected to the speakers. It now worked correctly on all six speakers, and I was confident that this would be the end to the sound problems. About a fortnight later, Trevor mentioned that when the receiver had been in use for a while, it would just stop working and the power indicator (red LED) would flash. If the machine was turned off at the power point and allowed to cool down, it would then recover and go back to normal operation. The day eventually arrived that the flashing red LED (signalling that the unit had gone into a self-protection mode) was a permanent feature. I went around to his place and removed the malfunctioning machine and took it back to my workshop. The machine was manufactured in 2005 and has two switch-mode power supplies on the PSU module (6870R8300AA). The main one supplies +12V, +5V and some other minor voltages, while the other supplies the +35V rail for the surround sound amplifier section. In common with most SMPSs, heat and time affect their reliability. I tested all the electrolytic capacitors with an ESR meter, getting a mixture of readings from high to none, particularly on the smaller value electros. These included C173, C175 & C176 (all 4.7µF/50V) and C115 & C125 (10µF/50V).There were also some high-ESR electros on the main PCB: C121, C137 & C138 (all 47µF/50V), all near voltage regulator IC’s. Having replaced those, I also replaced the following resistors with 2W metal film types: R104, R105 and R108 (the 220kW start-up resistors), R121 & R130 (both 100kW bleed resistors) and R138 (the 180W bleed resistor for the +5V rail). The PSU module was refitted into the machine and then powered up. The problem was still there! I downloaded a data sheet for the STRW6753 (power supply IC 104) and looked at the sample circuit diagram. I decided to order this IC on eBay as the next move. The IC arrived in the mail, and I fitted it, but it still did not fix the problem! There was still something not quite right. On a hunch, I decided to desolder one leg on every fast rectifier diode in the main power supply section. I then tested these for reverse leakage set on the multimeter’s highest ohms range. When I tested D129 on the +5V rail, it had some reverse leakage. It was a B10A45V fast diode, so I substituted one MURF1060 (10A 60V fast diode). It then worked correctly and did not miss a beat! After another two days of soak testing, I was confident that the power supply problem was finally fixed. Trevor was so pleased with the result that he bought me a carton of ginger beer and shouted the missus and I lunch at a nearby pub. RS-485 network with intermittent faults N. L. of Taylors Lakes, Vic, had to fix an RS-485 network which was having some odd problems. It turned 78 Silicon Chip Australia’s electronics magazine siliconchip.com.au out to be a part that you wouldn’t expect to be at fault... I was called to a network using an RS-485 physical layer (cable and interface cards in each machine) with 25 machines per segment and two segments. The two segments were connected by a network controller which polled each machine by their assigned network number, one at a time, up to the last machine numbered 25. The network controller was connected by USB to the PC, and then connected to the internet. The initial fault was that random nodes were not responding to the network controller at various times. This occurred on and off for months, and could not be isolated to a specific machine. Then the faults became permanent on one node in both segments. The cable was a 300W shielded pair, but the shielding was not connected continuously from one length of cable to the next or terminated on the network controller Earth either. One blessing the installer bestowed on the system was the 120W termination resistors were attached at the last machine on each segment. Swapping network boards, it was found that the network boards (two boards) on one machine in each segment were faulty. Back at the workshop, testing showed the boards to be working perfectly. I decided to change the line interface chip as they probably get a hiding from the cable. But the fault was still present with the boards reinstalled; luckily, I only changed it on one board. Back at the ranch, I hooked up the Silicon Chip Digital Audio Signal Generator (March-May 2010; siliconchip. com.au/Series/1) to deliver a square wave and noted that at the output of the line interface IC I had changed, it worked properly. Still, the digital receive signal was not present at the network board output. Between the MAX3062E line transceiver chip and the digital output to the machine microcontroller was an HCPL-2200 high-speed opto-coupler with a TTL output which was failing as the switching rate increased. Of course, replacing the opto-couplers solved the problem on both segments. I also re-cabled the longest segment with the correct 120W RS-485 cable with a continuous shield, using the original cable for the recommended reference point connections. Being differential, I am not sure what the reference point connection does. My theory is that it protects the line transceiver IC when one node powers down; any line over-voltages can dissipate into the powered nodes supply instead of through the unpowered transceiver’s internals. I welcome comments on that. I am now waiting to see how long the incorrect cable lasts before it gives errors. The customer (and the installer, whom I know) insists that I am wasting time and money replacing the cable since the existing one “works OK”. POWER SUPPLIES PTY LTD ELECTRONICS SPECIALISTS TO DEFENCE AVIATION MINING MEDICAL RAIL INDUSTRIAL Our Core Ser vices: Electronic DLM Workshop Repair NATA ISO17025 Calibration 37 Years Repair Specialisation Power Supply Repair to 50KVA Convenient Local Support Philips radio repair G. McD., of Jindalee, Qld got angry at his radio when it began resetting intermittently. Thankfully, he managed to calm himself down long enough to find the dodgy connection and fix it... My patience was pushed to the limit recently when my trusty Philips portable FM/DAB radio, an AE5230 model, shut down on me for the umpteenth time early one morning. siliconchip.com.au SWITCHMODE POWER SUPPLIES Pty Ltd ABN 54 003 958 030 Unit 1 /37 Leighton Place Hornsby NSW 2077 (PO Box 606 Hornsby NSW 1630) Tel: 02 9476 0300 Email: service<at>switchmode.com.au Website: www.switchmode.com.au Australia’s electronics magazine September 2021  79 All I was doing at the time was trying to increase the volume. The LCD screen died immediately, then after what seemed like a full thirty seconds, it lit up once more as details of the pre-tuned station began flickering across the screen. I barely avoided flinging the radio across the room in frustration. It had been acting like a temperamental teenager for months. Later that morning, I decided that enough was enough; it was time to see if I could fix the pesky thing. The first suspect was the DC jack at the back of the radio. Close inspection with a headband magnifier showed nothing obvious. So I had to open the radio up and delve a little deeper. I removed five retaining screws from the rear of the radio’s enclosure, allowing me to take off the back panel. I then identified the screws that held the main PCB in place. I removed these and unclipped the main power lead. The on/off switch was now clearly visible. I removed the two small securing screws holding the PCB upon which it was mounted. With the aid of a strong lamp and my headband magnifier, I inspected the condition of the three wires soldered to traces on the PCB. What I saw wasn’t pretty. The solder joints looked as though they had seen better days, and the wires were coated with some kind of dried goo. After desoldering the three wires (red, white and yellow), I cleaned up the through holes on the board with the aid of a solder sucker and refurbished the ends of the wires. I then cleaned up everything and soldered the wires back into place, and returned everything to its original position. I plugged in power and hit the on/off switch. All appeared to be working as it should, so I set it up once more on my bedside table. But the next morning, around 4:00AM, the radio spat the proverbial dummy once more. It was up to its old tricks, I thought, as I began pondering my next step. The problem had to lie with the power supply; I had been trying to adjust the volume at the time and in so doing, had moved the radio slightly to see the dial better. The DC jack was now my prime suspect. I placed the radio back on my workbench early the next morning and opened it up again. The DC jack is 80 Silicon Chip held in position in much the same way as the on/off switch, on its own PCB that is held in place by two small screws. Once I had removed them, it was an easy task to slide the PCB out for inspection. Under a strong light and with the aid of my headband magnifier, I noticed one of the soldered mounting pins had a hairline crack around its base. It was immediately evident that this was a result of stress from the slight sideways movements caused every time the plug is inserted or removed. All I had to do was re-solder the connections and put everything back together again — a simple fix to a problem that was not so simple to find. The radio has behaved itself ever since. Repairing two laptops that would not POST K. D., of Chermside, Qld, writes: in a previous Serviceman column (August 2014, page 61), I stated that I don’t believe in coincidences. Following some recent incidents, I might have to change my mind. A friend at a university biochemistry laboratory told me that two large ultrahigh-speed centrifuges in her laboratory both failed at switch on, within minutes of each other. Both emitted smoke and would need repair by the manufacturer’s technicians. The next day, at my workplace, two identical and quite critical refrigerators failed within 24 hours of each other, having not missed a beat in over five years. The third coincidence involved me, the same friend, and both of our home computers. It happened only a week after the coincidental failures at work. One night, my ageing Dell Vostro PC simply shut off mid-use. When I attempted to restart it, the fans all spun up, but that was it. The computer could not even generate a beep code from the power-on self-test (POST). As I was working at the time, I decided to leave any further investigation until I had a few days off. Before I could look at my PC, my friend called to say that her equally old Dell Inspiron PC wouldn’t switch on. This was worrying as she didn’t even remember when the computer was last backed up, or where the backup was stored. When she brought it to me, the symptoms were identical to mine – the power indicators were on, and the fans were spinning, but the PC wouldn’t even get to the POST. Australia’s electronics magazine I decided to tackle her Inspiron first. I checked the voltages from the power supply, and all were within specification. As the fans ran and responded to the power button, the motherboard couldn’t be completely dead. I disconnected everything possible from the motherboard and removed the memory modules and graphics card. The machine could still not get to the POST. On the off-chance that the BIOS had been corrupted, I removed the CMOS battery and turned on the power. At last, the machine gave four beeps, indicating that there was no memory. I fitted a new CR2032 cell and reconnected everything I had disconnected. The computer told me the BIOS had been changed and that the date and time were invalid. I was prompted to press ‘F1 for defaults’ or ‘F2 to setup’. I pressed F2, and the PC hung with an “ME unconfiguration in progress” message. ME means the management engine for the BIOS. This behaviour was reproducible when turning the computer on and off – pressing F2 wouldn’t get me into the BIOS. After the first power cycle, though, I had an option of pressing F12 for boot devices. Pressing F12 got me into the BIOS. All the settings looked usable except for the date and time. After setting those details and a ‘save & exit’, Windows started normally, and the computer was fixed. It was sent back along with some unparliamentary language about the need for regular backups. My Vostro has had a hard life, but it had the same symptoms as the Inspiron and I hoped it also had the same easily-fixed problem. So, I removed the CMOS battery and applied power, and that is where the similarity with the Inspiron ended. The computer still would not reach the POST. I progressively removed parts and applied power each time. When I removed the four 2GB memory modules, the POST test ran and indicated that the memory was missing. I fitted four replacement modules from a defunct Vostro obtained from a friend and reconnected everything. Pressing F2 at startup allowed me to reset the date and time in the BIOS and check that 8GB of memory was being detected. Windows then started normally, and another veteran computer was returned to service. SC siliconchip.com.au