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SERVICEMAN'S LOG How I got trapped inside my MG There are enough hassles when it comes to moving house without freezing because your car’s driver-side power window is stuck halfway down. Even worse is getting trapped inside a car that’s full of stuff and having to be rescued. Things have been rather unsettled in the Serviceman’s world recently. We’ve been moving house (and workshops) and it really is a wonder just how much (let’s be frank) “rubbish” two people can accumulate during 15 years of living together in one place. Like my electronics-enthusiast uncle in Melbourne and to a slightly lesser extent my Dad, I like to hold onto any stuff that comes my way, just in case I might need it one day. Some call this hoarding but I am a long way removed from those poor unfortunates who have to sleep standing up in a corner of their laundry, because every other room in the house has been stacked floorto-ceiling with old tat and random salvage. I can certainly relate in some small way to those folks and my heart goes out to them. However, I do know where to draw the line, although my wife may disagree somewhat. It’s not hard to understand why. After making at least a dozen trips to our new house with cars and trailers packed full of stuff, the contents of our old house and workshop still looked to be untouched! That’s not only terribly demoralising but also makes it impossible to deny that I/we have accumulated far too much junk. It’s at times like this that I could just as easily have had a skip parked next to the trailer and filled both with equal enthusiasm. I really need to ask myself: “do I really need this?” If the answer is “no”, then out it goes. It’s the only way to shed some of the extra tat we really don’t need. While we didn’t have a skip on hand, Dave Thompson* Items Covered This Month • • • • Dave’s moving house saga Three switchmode power supplies Healing satellite TV box Exorcising the gremlins from a mains electricity supply a lot of stuff did actually make it to either the recycle station, the clothing bin or the refuse-collector’s compactor. And to be honest, there’s a lot more that can go yet, now that we’ve finished renovating the new house and can turn our now-jaded renovator’s eyes towards the garage and workshop. Shifting house is difficult enough at the best of times; renovating the house before moving into it should be classified as a form of madness. We kept postponing the actual moving-in date, much to the dismay of the friend who was moving into the house we were vacating, mainly because various tradies hadn’t finished within their quoted time-frames. There was always some excuse as to why but if you take whatever time-frame they give you and double it, you’ll generally be closer to the mark! Power window problem I was hoping that things would at least go smoothly during the move but then an unexpected problem cropped up. On one of the last trips over to the new place, my MG filled to the brim with whatever stuff I could cram into it, I pressed the button to lower the driver’s-side window to let in a bit of air. Half-way down, the drive motor suddenly loaded up, let out a loud, nasty-sounding “bang” and stopped dead in its tracks. “Oh great, just what I need”, I thought. Fortunately, the weather was clear but it was very cold and the wind carried the freezing bite of snow falling somewhere to the south of us. I was on a high-speed ring road at the time and despite juggling the switch, it quickly 66  Silicon Chip siliconchip.com.au became obvious that it was going to be open for the rest of the journey. No worries, Kiwis are made of pretty tough stuff and a little cold never hurt anyone. Once I got to our new place and had unloaded the stuff, I had a look at it to see if I could at least close the window, as the sky was threatening rain (or worse) and I didn’t fancy driving back across town with it stuck down. First, I gave it a good heft and managed to move it in the track a little. I then pushed the switch and, with a bit of help from me, the motor strained and whirred away until the window eventually reached the top. I wasn’t prepared to try opening it again and simply drove the car back to our old place, where I’d be spending another few nights before finally changing locations. The next day, with the car once again piled high with more of our earthly possessions, I headed off to the new house. However, when I got there and went to open the door to get out, the handle felt unusually stiff. I pulled on it a little harder than usual and following a loud internal “thunk”, the handle suddenly became very loose. Obviously, the cable that actuated the door latch had parted company with the handle mechanism somewhere. With a sinking feeling, I recalled that the previous day, while helping the window into place, I’d felt (and heard) something “give” inside the door. At the time though, I assumed that it was something related to the window’s scissor mechanism. Now it appeared to be more to do with the door opening mechanism! Whatever it was, this presented me with a bit of a problem. I couldn’t lower the window, I couldn’t open the driver-side door and the passenger compartment was jammed full of bags and boxes. I can report that the air was turning bluer by the second! At that moment, a builder friend who has been helping with the renovations drove up in his van. Saved! I shouted out the problem and he tried to open the door from the outside but without success. The exterior handle apparently wasn’t attached to anything inside the door either. More blue air followed but no matter; he could at least unload the gear from the passenger side and I could clamber out that way. And that’s eventually how I extrisiliconchip.com.au cated myself from my MG. It wasn’t very elegant but at least I was out! After dealing with the stuff I’d brought over, I set about looking at the door. Problem number one was how to open it. Neither handle worked, the window didn’t want to move and I couldn’t remove any panels from the inside of the door unless the door was open. This was turning into a real chicken-and-egg scenario. My builder friend and I tried some of the more obscure methods of opening the door but nothing worked. We even tried the old hand-saw trick; something I’d seen done many years before and had actually pulled off once on a Nissan van I’d owned. However, while it might work for unlocking doors to retrieve locked-in keys, it certainly wasn’t about to open this door! Still, we had a van that was loaded with tools and a temporary computerservicing workshop that was also full of tools; surely we had something that would help us open this door! The problem was that the mechanism to unlatch the door needed to be actuated, yet all approaches to it were obscured or simply not an option. By now feeling quite frustrated, I sug- gested cutting a hole in the internal door panel (I have a spare set) but my friend’s calmer mind prevailed and after a lot of jiggery-pokery, we eventually managed to move the window down in its track. This involved him leaning on it different ways while I operated the switch and bit-by-bit we moved it, very choppily and noisily, most of the way down. Apart from everything else, something was also very wrong with this window mechanism! With the window down, we now had access through the top of the door and could see the door-latch assembly a lot more clearly. All we had to do was figure out how it operated. Eventually, after a lot of poking and prodding, we discovered that the part that is actuated by a cable when either handle is toggled had popped out of its plastic housing. Usually, it was clipped securely in place but the Nylon bushing had come apart and so it wasn’t holding onto anything at all. All I had to do was get something onto that mechanism and actuate it to open the door but that was a lot easier said than done! Finally, I made up a tool from a 700mm length of thin aluminium tube I’d salvaged from a 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? In 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 car electronics. 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. October 2016  67 Serr v ice Se ceman’s man’s Log – continued Three switchmode power supplies Faults in switchmode power supplies can sometimes be difficult to track down. R. L. of Oatley, NSW recently tackled completely different faults in three switchmode power supplies, each with complete success. Here’s how he did it . . . I retired some years ago after working as an electronics engineer in the aviation industry. However, friends still ask for my assistance and advice when their electronic gadgets, radios and toys, etc fail. Recently, I was asked to look at three totally different devices that had failed: a docking station, a washing machine and a DVD/VCR machine. The first item was a Phillips AJ72­60D/79 clock/charging station which was completely dead. I removed the bottom cover and found a brown stain on the inside beneath the power supply. As there appeared to be no external spillage from the top, I guessed that something in the supply itself had failed. On removing the supply, it was obvious that the main capacitor (EC1) had exploded. So was this due to something else failing or was this the only fault? I checked along the input path from the 230VAC connection and found that fuse F1 had gone open circuit and that thermistor RT1 had cracked from overheating. Further checking showed that the rectifier was OK and that switching transistor Q1 had no signs of heat stress. I obtained the replacement parts, reassembled the unit and powered it up. It functioned perfectly. The second item, a Simpson EZISET 550 washing machine, was apparently working OK one day and dead the next. After dismantling the top control panel, I checked that all the switches were functioning correctly and that power was getting to the control module, which it was, so it looked like the module itself was faulty. As a result, I removed the control module and took it back to the workshop. After prising the circuit board out of its plastic cover, I discovered that the LNK306 power supply switching module (U1) skip somewhere (see, I knew it would come in handy!) and an Allen wrench which was taped half inside one end. This was carefully eased through the window gap and then, bit by bit, a slight curve was formed in the tube until I got the Allen key onto the latch. Once it was in-place, it was almost an anti-climax as to just how easily the door popped open when I pressed on the mechanism. What a palaver! With the door open, it was a simple matter of removing the door panel to reveal the goings-on inside. Straight away, I could see where the window’s scissor mechanism had come apart. Two separate steel levers formed a stamped and spot-welded “X” section and this created a fixed-point around which the mechanism pivoted. I was 68  Silicon Chip had a crack in it and that the surrounding jelly-like coating had blackened. I checked all the other components between the 230VAC connections and U1 and they were OK. I ordered a replacement LNK306 (U1) on-line and installed it as soon as it arrived. The machine then ran flawlessly. The third item, an LG RC689D DVD/VCR, had suffered a substantial power surge. I disassembled the unit and removed the power supply board. It was immediately obvious that there was some major damage. I set about tracing out the circuit with the aid of an application circuit for the STR-W6200D switching IC that I’d found on the internet. The input diode bridge, the filter capacitor, the limiting resistor, two zener diodes and the switching IC (but not the input fuse) had all been destroyed, so I ordered the appropriate parts and waited. Once these new parts had been installed, the unit powered up and everything worked fine, hopefully for many more years. going to need a new scissor mechanism but in the meantime, I fudged it back together by drilling a hole through both pieces and using a short bolt, nut and washer to secure them. The window then worked, although not very well and not through its full travel. But at least I could open and close it a bit. The handle mechanism problem was quite different. A right-angled piece of steel rod on the end of a short cable was supposed to hook into the door actuator assembly, with a Nylon clip preventing it from pulling away. However, this clip had broken. In fact, the assembly appeared to have been caught in the window scissor mechanism while I had been manhandling it the previous day. This had pulled the cable away from the latch and broken the clip. The nylon clip obviously had to be replaced but in the meantime, I needed to be able to enter and exit the car without clambering through the passenger door! I tried putting the clip back together and gluing it with epoxy but it simply pulled apart when the handle was pulled. It was obvious that the clip wasn’t going to hold together, so I scrounged through my parts boxes and found a nylock-style nut that was slightly smaller than the diameter of the steel rod on the end of the cable. My aim was to thread the end of the rod and use the nut to hold it onto the latch, rather than rely on the plastic clip. To make things easier, I removed the latch mechanism from the door siliconchip.com.au so I could work on it outside the car. Using a socket, I forced the nut onto the rod and with a drop of machine oil to lubricate it, used it as a crude die to cut a thread. Eventually, I managed to get it on far enough so that it was secured by the nylock section, so it wasn’t going to come off in a hurry. In the end, it worked so well that I don’t think I’ll bother trying to source a new clip for it. Besides, now that the end of the rod has been threaded, it would probably tear out the inside of a replacement plastic clip anyway. Collateral damage Another instance of collateral damage during the move involved my headphones. I usually have a reasonably good set of speakers connected to my computer but in the interests of domestic harmony, I also use a nice set of headphones when the situation requires it. These aren’t fancy, expensive headphones but they are good, cover-theear types that don’t give me a headache. Many larger style headphones don’t work well with people who wear glasses, such as myself, as they press on the arms and cause discomfort. However, these ones are just right and I was a bit annoyed when they started behaving badly after the move, with audible crackling and the audio cutting out on the righthand side. I discovered that I could affect the sound by flexing the cable where it entered the left headphone cup, so it appeared something had come adrift inside. From memory, these headphones only cost about $12, so most people would just bin them and buy another set. However, as a serviceman, that goes against the grain and so it was out to the workshop with them. After a rummage around to find the necessary tools to strip them down, I set about finding out what was going on. Most headphones come apart the same way; popping off the ear cushion reveals screws that hold the cup together. Once these have been removed, the ear plate comes away, usually with a speaker attached, and with trailing wires leading off to the rest of the set. In this case, there was a small circuit board which was held on with a couple of screws at the base of the left ear-cup. Flying leads then ran from this board to the lefthand speaker and via the headband to the righthand speaker. What was rather odd was that a 3.5mm stereo socket was mounted on this PCB and the audio cable terminated into it via a standard 3.5mm stereo plug. It’s really a good idea, as it makes it easy to change the lead, should that be required. What wasn’t such a good idea was the long, stripped speaker wires that were touching each other and other pads on the PCB. Flexing the cable where it entered the cup moved the PCB and wires slightly and this caused the audio interruptions. The repair simply involved shortening the wires and re-terminating them with heatshrink insulation installed. The audio was then once again cracklefree and achieved without needlessly throwing away a perfectly good set of headphones. Healing satellite TV box N. G. of Gymea recently struck problems with a Healing satellite TV receiver that conked out each time he tried to point the motorised receiving dish in a new direction. Here’s how he tracked the problem down . . . I was a self-employed TV serviceman for most of my working life and still maintain a keen interest in hobby electronics, thanks largely to SILICON CHIP and its predecessors. My main lounge-room amplifier (still in daily use) is a Twin 17 Watt Ultra Linear Valve design, published by John Moyle in Radio TV and Hobbies and built while I was a student in 1959. My wife and I were never able to find one that sounded better but I guess that’s another story! Several years ago, while heading for retirement and with more time to pursue the fun stuff in electronics, I decided to have a go at satellite technology. This was done with the help of Geoff, my first apprentice and still a good friend. He rounded up a secondhand dish and LNB (low-noise block)and suggested that to make full use of what was available, a dish motor would be a very worthwhile addition. This has proved to be every bit the case, as the free-to-air stations available in Eastern Australia that are worth having are well and truly scattered across four different Ku-band satellite locations. Of the hundreds of un-encrypted channels which can be viewed, I filter out 40 or so which are of some interest Are Your S ILICON C HIP Issues Getting Dog-Eared? REAL VALUE AT $16.95 * PLUS P & P Keep them safe, secure & always available with these handy binders Order now from www.siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number. *See website for overseas prices. siliconchip.com.au October 2016  69 Serr v ice Se ceman’s man’s Log – continued The gremlins really had fun with the electricity supply at A.L’s home in Turramurra, NSW. At odd times, the power would switch off for no apparent reason and it took months to find the cause . . . “There’s no power dad – can you fix it?” That was the question from a family member some months back when our internet router went down, along with the dishwasher, the kettle and all sorts of sundry chargers, lamps and printers etc. It was just the usual family excess use of all the available power outlets. “OK, that should be easy”, was my answer (famous last words). I soon discovered that a circuit breaker (in combination with an RCD) in the fusebox had flicked off. However, before switching the power back on, I switched off all the chargers, desk-lamps and other items, including the kettle. The power was then restored without incident and all was normal for about the next two weeks. And then one evening, the same thing happened again, just as the dishwasher was in the middle of a wash cycle but without much else on. Aha! – now was the time to see which utensil was causing the prob- lem! I removed everything, restored power and then plugged things in one-by-one to make it easy to establish the culprit. Wrong! Nothing seemed to trip the circuit breaker or RCD and even when I switched everything on, the power remained intact. At that stage, I put it down to a possible surge from the mains because our voltage is relatively high. I measured it at 251V RMS at the time it cut out (off peak) and assumed (incorrectly) that any slight surge may be sufficient to flick the circuit breaker off. All then went well for about two months and then it started to happen again, usually when the dishwasher was on. It got to the stage where my wife was insisting that everything be turned off (including the router) when she wanted to use the dishwasher and so I began checking the prices of new dishwashers, fearing that the one we had might “blow up” for good! After a while though, nothing seemed to make sense, as the power seemed to cut out intermittently at any time of the day regardless of which appliances were being used. What’s more, none of the appliances had any apparent faults! I also checked the wiring with an RCD tester, fearing that there may be some kind of problem like a short circuit or leakage to earth. However, the system responded perfectly and only turned off at the specified 30mA and was OK at 10mA and 20mA. What’s more, a static current measurement using a clamp ammeter showed no measurable residual leakage at all! Then one day there was a “hallelujah moment” when my wife shouted “I’ve discovered the problem, it’s the microwave oven!” She had switched it on at the power point and the circuit breaker had cut out at the exact instant. We quarantined the microwave oven but left it sitting on the kitchen bench while we celebrated our apparent victory. Alas, two weeks later, while we were watching a movie, the power failed again! So it wasn’t the microwave after all; it had just been coincidence. I ventured out to the fusebox in the darkness and rain to switch the circuit breaker back on yet again but this time I noticed a distinct smell coming from it. It was also warm to the touch! “Wow”, I thought, “there must be a lot of current through it to do that”. Either that or perhaps there was a problem with the internal working components of the circuit breaker itself. It was a 20-year-old unit (a Clipsal 4BE216/30) and it now became the main suspect in the mystery. I and save them as favourites. There are many very useful programs that are not normally seen in Australia, even with pay TV. The satellite FTA choice seems to be definitely improving (perhaps being spurred on by all the free TV on the internet?). The time shifting that is in effect provided by the ABC and SBS due to Australia’s different time zones can also be very useful. An FTA standard-definition (SD) satellite receiver was part of the original package (Strong SRT 4663X) and was good enough for a while. However, with increasing numbers of channels being only available in HD with MPEG4, I eventually decided to buy a new Healing HHS242 satellite receiver. This HD FTA receiver performs remarkably well for its size and price and incorporates Disec 1.2, giving full control of the dish motor (a Sadoun DG-280) via the single RG6 connecting cable. It all worked perfectly for the first 18 months or so, the motor drive always moving the dish to the exact location required in very little time. At the end of this period, it suddenly ran into problems, with a “No Signal” message displayed on the TV screen. When I checked the problem out, I noticed that the dish was pointing much too far to the west. However, I was able to perform a motor reset to the north reference point and it then operated normally again – for a while! This same problem was subsequent­ ly repeated several times, so I searched the internet for clues. This threw no light on my particular problem but I did discover that a firmware upgrade was available for the HHS242 receiver, mainly to deal with a sound issue. I held out a vague hope that installing this upgrade might improve things but no such luck; the problem was every bit as bad after the upgrade and, in fact, was becoming more frequent. The problem subsequently progress­ ed to the point where I was unable to even perform the motor reset, the dish remaining stuck pointing too far to the west. When I attempted to use the remote control to move towards the east, the notation on the screen was exactly as you would expect – a little flashing arrow indicating movement to the left but with no actual physical change in the direction of the motor itself. Exorcising the gremlins from a mains electricity supply 70  Silicon Chip siliconchip.com.au This photo shows the obvious signs of the heat generated on the output terminal of the RCD due to a loose wire. subsequently had it replaced and all returned to normal. As it turned out, it was not really the fault of the Clipsal unit itself. If you look at the accompanying photo, you will see that one of the screw connectors had come loose, possibly because it had not been sufficiently tightened, and this had caused a hot spot as it was not making a good connection to the outgoing Active wire. And because it was on the bottom of the unit, the rising heat was causing the circuit breaker, which is tripped by heat, to turn off. It’s probable also that vibration caused by constantly opening and closing the fusebox and operating the switch exacerbated the loose connection. In fact, subsequent checks revealed that there was nothing wrong with the Clipsal device and except for a slightly burnt terminal, it still works as specified. It was replaced for good measure anyway. I connected a meter to the receiver’s LNB input socket and this gave readings of 13.5V DC when the receiver was tuned to vertically polarised transponders and 18.4V for horizontally polarised ones. This was exactly what you would expect and made me inclined to suspect the dish motor rather than the receiver. I then wired up a temporary RG6 adaptor lead which allowed me to measure the output voltages with the LNB and motor connected together. This time, the reading was 0.56V regardless as to where the receiver was tuned, so obviously the LNB and motor would be unable to function. So was the dish motor placing an unduly heavy load on the receiver and causing it to effectively shut down? siliconchip.com.au Or was it the LNB that was causing the problem? Or was the fault in the receiver? I have learned over many years of involvement with electronics to be very careful about what I throw out (much to the annoyance of my wife). And fortunately, I’d had the good sense not to dispose of my old SD satellite receiver. This was now reconnected so that I could check the LNB and dish motor without the Healing HD receiver. I was a little surprised to find that the motor and LNB now operated perfectly; in fact all of the original satellite locations were still remembered! When I reconnected the Healing receiver, I got another surprise. It was now doing a perfect job of receiving all of the usual channels on Optus C1/ D3. I then realised that this just happened to be where the dish had been left pointing when I disconnected the SD box after testing. The receiver now appeared to be fully operational for C1/ D3 but it shut down instantly when I tried to receive a channel from a different satellite. Clearly, it was sheer luck that the HD receiver happened to be tuned to the C1/D3 channel when I first reconnected it, which coincided with the dish position. This indicated that most of the receiver was working normally but it would shut down each time I attempted to move the dish to a different location. The receiver was thus able to operate normally with DC power provided just for the LNB but was unable to provide the extra “grunt” necessary to turn the motor and drive the dish to a new location. This indicated that the receiver’s 13V and 18V supply rails were unable to cope with the dish motor when needed. On the other hand, these supply rails must still be present, otherwise it would not have been possible to receive any channels from the LNB. So how hard could a power supply problem be to track down? It was definitely worth a shot. When I opened the box, I found a finely detailed double-sided PCB with numerous plated through connections. Unfortunately, the component labelling was sparse and there was no separate power supply board; everything was bundled together. Indeed, it appeared that this device was not made to be repaired. I thought that the logical place to start was with the electrolytics, so I used my trusty SILICON CHIP ESR tester to check all 11 of them. This didn’t reveal anything unusual and after taking into account the young age of the unit, the fact that all the electros were 105° types and the plated-through connections, I decided to do a bit more checking before replacing any of them. The distributor was unable to provide a circuit diagram, so I did an internet search for any technical details using the various letters and numbers on the PCB. This led to nothing of use so I then tried to make some sort of sense of what the circuit was doing. The main power supply itself appeared to produce just two outputs, nominally 5V and 12V, both of which measured OK. So where did the 18.3V and 13.5V for the dish motor come from? There would have to be a switching voltage convertor of some kind involved near the LNB input side of things, so I decided to start with the electros in that area. Because replacement would not be easy (due to the plated through PCB holes), I initially tried bridging the electros in that area of the PCB but to no avail. I then carried on bridging the electros in what looked like the main power supply area itself and that’s when I struck pay dirt! Capacitor EC3, a 220µF 25V electrolytic across the 12V rail, was the culprit and bridging it with a similar value immediately restored the ability of the unit to rotate the dish motor without the receiver shutting down. When removed from the board and tested again, its ESR was certainly too high at 5.6Ω but when it was in-circuit, it was well under 1Ω. This would not be the first time that removing an electro was the only sure way of testing its ESR but I must say that the symptoms displayed by the unit were rather strange. It’s several months now since the repair and there’s been no hint of further trouble. Finally, I can’t help pondering what I would have done if the Healing HD receiver had been tuned to a different channel to the SD receiver when I reconnected it. In that case, it would have immediately tried to initiate dish movement and would have shut down, leaving me unaware that it was still capable of receiving channels. And that may well have dampened my enthusiasm for proceeding further with this repair. So I was lucky – Murphy must have been on holiday SC at the time! October 2016  71