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SERVICEMAN’S LOG Off on spring break Our resident Serviceman is taking a deserved break this month from his regular column, and is enjoying himself on a beach far away. This month will be all from contributors, with a return to normal schedule next month. Converting from one problem to another P. M., of Christchurch, NZ used to repair monitors and power supplies for an arcade machine manufacturer, so he has a fair bit of experience. In this case, the equipment to be repaired was very complicated, but the fault turned out to be pretty simple... While I repaired monitors and power supplies, two other technicians repaired the game logic boards. Having little digital experience at the time, I was in awe of them being able to find faults on boards full of digital chips. Sometimes, I would see them with their hands spread over the boards. When I asked, they explained that they could find chips getting too hot or not getting warm, which could lead them to the fault. Now you can use an infrared thermometer to do the same job. 96 Silicon Chip Recently, I was asked to go to my friend’s recording studio to sort out some gremlins. About 15 years ago, he retired the ageing 24-track analog tape recorder in favour of a digital equivalent. This came in the form of a potent computer with expansion cards to connect to three external 8-channel analog-to-digital (ADC) and digital-to-­analog converters (DACs). After some diagnosis, it appeared one of the converters had output signals that were very low in level and distorted. The converters are housed in 1RU rack-mount cases in their own rack, with spaces between them for ventilation. When I put my hand on each of the first two, they were warm, but the third was considerably cooler. My friend was a little sceptical, but I insisted I had located the problem. I figured that a power supply rail had failed, leading to the distortion. My guess was it would be one of the ±15V rails feeding the audio op amps. Back in my workshop, I plugged the unit in but could not get the power LED to come on. A look inside revealed a small relay next to the power jack. An external 9V AC power pack powers these units; it appears that the host computer powers the relay to turn the units on and off. So I removed the board and shorted the relay contacts to get things going. The board had four regulators on it: one +15V, one -15V and two +5V. I checked the 15V regulators first, but both were working correctly. The first +5V regulator was OK, but the second had no volts on its output or its input. I checked the circuit diagram, which showed a diode in series with the regulator input. The diode tested fine with a meter, but my scope showed 9V AC on one end and nothing coming out on the other. A replacement diode brought it all back to life. Further investigation revealed that this regulator powered the Australia's electronics magazine siliconchip.com.au Items Covered This Month • • • • • • Recording studio 8-channel DAC repair Beyonwiz DP-S1 PVR repair The electric oven also took a break Repairing a Daikin air conditioner Range Rover excessive battery drain Smoothing out problems on a dot matrix printer Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com digital-­to-analog converters driving the outputs, hence the distortion and low levels. Beyonwiz DP-S1 PVR repair B. P., of Dundathu, Qld is becoming an old hand at repairing PVRs as he has written in several times now with such repairs... Back in 2014, I bought a Beyonwiz DP-S1 on eBay. Unlike my later Beyonwiz purchases, the DP-S1 was in good working order and served as my main personal video recorder (PVR) for some time. After that, it became my secondary PVR as these PVRs will only record two channels at once, so if there was a third or fourth program that I wanted to record, I used the DP-S1. In 2022, the DP-S1 started getting a bit flaky, flashing the screen on and off a few times when it was first turned on. However, it settled down each time and continued to work for a few more months. Then I turned it on and got a message that the HDD was not initialised. I suspected that the HDD might be on its way out, so I formatted it. As I no longer had any files on the HDD, I turned it off. The next time I tried to turn it on, it would not turn on at all. It seemed more like a power supply problem now, so I would need to take the lid off and look to see what the problem was. These PVRs (like any other appliance) are subject to electrolytic capacitor failures, and I have repaired several Beyonwiz PVRs with such faults. The lids are usually removed by undoing four screws on the back and one on each side. However, the DP-S1 is different to the other Beyonwiz models as it has ‘wings’ on the side. After removing the back screws, the lid would not come off, and I had no idea how to remove the wings to remove the two screws on the sides. A check on YouTube proved fruitless, as this model is now at least 15 years old, but I found the answer on the Beyonwiz forum. It’s simply a matter of turning the DP-S1 over, pressing the clip and sliding the wing forward; very easy when you know how. With the wings removed, I could undo the two side screws and take off the lid. I could see the problem straight away. There were three bad electrolytic capacitors on the power supply board. This is typical of how these units fail, often coming up with an ERROR 0000 message. Removing the power supply board was slightly more difficult than later models due to the DP-S1 having a DVD drive, as the power plug for the DVD drive is under the drive and a bit hard to remove. After undoing the five siliconchip.com.au screws holding the PSU in, I was able to reach under the DVD drive and pull out the power plug. With the DVD power cable unplugged, I then removed the IDE cable from the hard drive so that I could unplug the power plug to the hard drive at the splitter. The next step was to desolder the three bad capacitors from the power supply board and look through my reclaimed capacitors and find suitable replacements. It’s important to note the orientation of electrolytic capacitors, as they are polarised and tend to explode if fitted backwards. Ask me how I know that! It’s standard convention to mark the negative side of the capacitor on the PCB, but on rare occasions, the positive side will be marked instead, so you have to pay attention. Having found suitable replacement capacitors, I first tested them with my ESR meter, then soldered them onto the power supply board and put everything back together. I only repair my own gear, so I don’t have any problem using reclaimed components. I’ve even had times when a new capacitor failed after just a few months; I then replaced it with a good used one, in the next voltage range up, and that capacitor has been working for several years. Just make sure to test reclaimed components to verify they are OK before reusing them. Now it was time to test the DP-S1. I turned it on, and it started up with no problems, indicating that the previous screen flashing and the HDD problems had been caused by the bad electrolytic capacitors. I then checked the program guide, and that loaded correctly also. While the DP-S1 only has a 180GB hard drive, it serves the purpose of occasionally recording when there are several programs on at the same time. I also sometimes use it to play DVDs. As far as I know, this is the only Beyonwiz model with a DVD drive. As it was working again, I decided to address another problem that had existed for many years; it had no front panel display. When I first got the DP-S1, the front panel display was a bit on the dim side, and over time, it faded out completely. This is a known problem for this model. It is caused by, if you haven’t guessed already, bad electrolytic capacitors. One post from Warkus (Mark) indicated that the failure of four particular capacitors caused this. Mark has posted a lot of very useful Beyonwiz repair information on the forum. There were bad electrolytic capacitors on the power supply board, shown above. The repaired PVR system is shown at right. Australia's electronics magazine June 2023  97 As I had already replaced the three large bad electrolytic capacitors, it was time to test the rest of the small capacitors to see which ones were bad. Here’s where my trusty ESR meter comes into play. Often, bad capacitors stand out with their blown tops or the bottom seal pushed out. Still, in some cases, they go bad without any visible sign. I checked over the board and found that C7, C31, C35, C37, C44 and C45 were bad. The majority of these capacitors read open-circuit on my ESR meter, while the others had very high readings. As I found each bad capacitor, I marked it with a felt-tipped pen. Then I drew a sketch of the PCB, removed the capacitors one at a time and marked on the sketch the value and the voltage of each one. I have most of my salvaged capacitors sorted into voltage and size ranges, so I located the correct replacements without too much trouble, soldered them onto the PCB and reinstalled it. I connected the power and turned it on, and I was greeted with a working front display. There is a saying that electronic equipment’s reliability is inversely proportional to the number of electrolytic capacitors it contains. This often proves to be the case, and I’ve repaired many devices with just bad capacitors. I’ve lost count of the number of devices I’ve repaired with this fault, including PC power supplies, older computer motherboards, two digital clocks, several PVRs, several monitors and two touch lamps, to name a few. Next to my multimeter, my ESR meter is one of my most valuable tools, along with my transistor and diode tester, both being Electronics Australia designed kits from Jaycar. If my ESR meter ever fails, I have a Silicon Chip ESR meter kit on standby that I can assemble if I need another. The unconventional oven? R. W., of Mount Eliza, Vic had a bit of a shock when his oven quit just before guests were due to arrive for lunch. Could he fix it in time? Sometimes the solution is not what you expect... Our ILVE electric oven was not working on Australia Day, not long before our lunch guests were due to arrive. Earlier that day, the light in our room went out. Upon examining the switchboard, I found that the safety switch had tripped. Switching it back on, the TV started working again, and the lights came back on, but the oven clock was not working. I checked the oven circuit breaker in the switchboard; it had not tripped. To ensure the oven circuit breaker was on, I switched it off and then on again. But the oven clock was still not working. I got my trusty old Fluke multimeter out to see if power was getting to the oven, which is hardwired. So the only way to measure the voltage was at the bottom connection of the oven circuit breaker. But the Fluke multimeter was reading just over 100V AC, not around 230-240V AC as I expected. It also indicated that the supply voltage from the street was just over 100V AC. The TV and lights were working, so I thought the Fluke multimeter battery might need replacing. However, its battery monitor indicated that the battery was OK. So, maybe the 50-year-old multimeter was faulty. I remembered that our SolarEdge inverter also indicated what the grid voltage is. On going into the garage to check it, I noticed that only one of the two lights worked. I found that the SolarEdge inverter was not functioning. That made 98 Silicon Chip me think that perhaps the TV was working because it supported an input voltage range of 110-240V AC, as much equipment does these days. It used to be that mains-powered devices had a switch or link to choose between 110-120V AC and 220-240V AC operation, but that’s far less common these days as most devices use switch-mode supplies with a wide input range. So I phoned United Energy, the company that owns the poles and wires in the street. After a few button presses, the answering robot indicated there was a problem with the electricity supply, but it did not say that the electricity supply was off. It also said it should be fixed by 11am today. Presumably, the computer knows your location from your phone number. So this pretty much confirmed that the TV and lights were working with the supply voltage down to around 100V AC. I decided to determine what else was also working at 100V AC. The WiFi modem was working; the electric kettle display was working, but it took a lot longer for the water to boil; the microwave oven display was working, but it only made food warm and not hot. The display on the LG fridge was working and indicated that the fridge and freezer temperatures were OK, but that does not mean it would have been able to maintain these temperatures all day. It was also good to know that the trusty 50-year-old Fluke multimeter was still working. Later that morning, an SMS from United Energy said, “We’ve restored power from the outage that was caused by a wildfire.” I found that both lights in the garage were now working, and the oven was too, just in time to have lunch ready before our guests arrived. All had a good Australia Day lunch. Component-level repair of a Daikin aircon B. C., of Dungog, NSW spent quite a bit of time investigating why his Daikin air conditioner was no longer working. It turned out to be a reasonably simple fault to repair, once he had pinned down the component that was on the fritz... One cold winter’s morning, we switched the kitchen air conditioner on to get some heat, but no air came out Australia's electronics magazine siliconchip.com.au IPX R ATEX D Keep your electronics operating in Harsh Conditions WATER RESISTANT SWITCH PANELS FOR BOATS OR RVS FROM 7995 $ Marine Switch Panels LOCKING LATCHES FOR EASY ACCESS • IP66 water resistant • Integrated 6-20A circuit breakers • LED illuminated switches • Pre-wired - easy install 4 Way SZ1906 | 6 Way SZ1907 Sealed Diecast Aluminium Boxes • IP65 dust and hoseproof • Internal guide slots • 6 sizes from 64Wx58Dx35Hmm to 222Wx146Dx55Hmm • Flanged versions available HB5030-HB5050 Industrial ABS Enclosures • IP66 weatherproof • Stainless steel hardware • Supports DIN rail components • 2 sizes HB6404-HB6412 FROM 1595 $ Switches for wet & dusty conditions 21 $ FROM 3995 $ STRONG, SAFE & SEALED 95 EA Durable Metal Pushbuttons • IP67 dust & waterproof • 12V LED illuminated (red, green or blue) • DPDT momentary action • SPDT with blue power symbol SP0800-SP0810 FROM 16 $ 95 Illuminated Pushbuttons • IP65 dust & water resistant • Momentary or On/Off • DPDT SP0741-SP0749 Explore our wide range of harsh environment products, in stock on our website, or at over 110 stores or 130 resellers nationwide. Other harsh environment products include: • 15 x Sealed IP65 Polycarbonate Enclosures • 14 x Sealed IP65 ABS Enclosures • 9 x ABS Instrument Cases with Purge Valves • Range of Waterproof Multi-pin Connectors, including Deutsch-type • Range of Sealed Rocker & Toggle Switches • 10 Waterproof Cable Glands jaycar.com.au/iprated 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. The control PCB for the Daikin aircon. of the head unit at the end of the start-up cycle. The Daikin RY60GAV1A A/C was a fixture in the house when we moved in about eight years ago. Holding the CANCEL push button on the remote control for more than five seconds allowed me to enter the FAULT CODE MODE. Then repeatedly pressing the CANCEL pushbutton allowed me to go through all the codes listed and finish at 00 (normal operation). All of the fault codes and their meanings are on a label under the hinged filter cover of the head unit. For example, if there was a long beep after pressing the CANCEL push button with C4 displayed, there could be a problem with the indoor thermistor. However, when I went through the list, there were no long beeps. It appeared that there could be a fault in the outdoor unit, which might not be one of the listed codes. I isolated the power and removed the top cover of the outdoor unit. I checked all the wiring in the outdoor unit but found no broken or loose connections. After powering it up again, I found that the outdoor fan would start up after about two and a half minutes, and I heard a solenoid valve operate at about four minutes. However, the compressor did not start. At the right-hand end of the outdoor unit, in its own compartment, is a large control PCB labelled EX304-3. This PCB is populated mainly with leaded components. Of interest were the Fujitsu MB88515B microprocessor IC, Toshiba TD62004 7-channel Darlington array and seven magnetic relays MRn (see the photo above). I noted that the green LED (near the microprocessor) was flashing at about 1Hz, indicating that it was running OK. I isolated the power again, removed the control PCB and took it to the test bench. I tested all the electrolytic capacitors (ELNA brand) with an ESR meter and found them all to be within specifications. 100 Silicon Chip At this point, I decided to download a PDF of “Manual ED01-214A Daikin Room Air Conditioners GA (old)-­Series”. I printed out the wiring diagrams for the RY60GAV1A model on pages 7 and 8 and the piping diagram on page 10. These are a bit basic as to what is on the PCBs, but they were a good starting point for me to reverse-engineer things. When I went to download a data sheet for the TD62004 IC, it turned out to be equivalent to the common ULN2004 IC. I refitted the Control PCB back into the outdoor unit to perform further diagnosis, so I could determine why the compressor would not start up. I dismantled the Main Power Relay (K1Main) near the compressor and found that the contacts only needed a light dressing with a points file. This was despite many cycles of usage. The relay coil measured OK, and when mechanically operated, there was continuity through the double-pole contact set. After powering up and then waiting for the correct part of the cycle (compressor start-up), I found no voltage present across the coil of K1Main. Mains voltage should come through the MRcompressor PCB-mounting relay on the control board. So I once again isolated the power, removed the control board and swapped the MR1 and MRc magnetic relays. This was to no avail; after refitting the control PCB and powering it back up, it still wasn’t working. It was now time to go down to the component level and make some voltage measurements directly on the control PCB. The TD62004 IC measured +12V on pin 9 (Vcc), and each channel input should be at +5V when driven high from the microprocessor IC. Each magnetic relay (MRn) coil is fed from the +12V supply and then grounded through its own Darlington transistor when activated by the microprocessor. The outdoor fan input was on pin 5, the solenoid valve input on pin 1 and the compressor input on pin 3. Even though there was +5V present on pin 3 (from the output of the microprocessor), there was still about +9.5V on that channel output at pin 14. There would need to be close to 0V if the 12V coil of the magnetic relay MRc was going to pull in! Obviously, this channel was faulty, and the IC would have to be replaced. While I had previously found that the ULN2004 was equivalent to the IC used, I could only find a ULN2003 in my collection. However, after perusing the data sheet, the ULN2003 appeared to be a better choice. The ULN2004 required a minimum drive voltage of +6.2V and, in this application, the ULN2003 would work better with the +5V signals from the microprocessor. I duly fitted the ULN2003 and put the control PCB back into the Daikin outdoor unit. After powering it up, it was a great relief to hear the compressor starting at the correct time in the cycle and to have warm air coming out of the indoor head unit. The air conditioner has run faultlessly ever since. Sourcing parts for a Range Rover TD4 J. N., of Mt Maunganui, New Zealand recently had a strange problem with his 2005 Range Rover Freelander TD4, which he has named “Polly”. Getting parts for older vehicles has become a problem, so it’s good he was able to fix the faulty component… My wife needed to attend a doctor’s appointment, so we Australia's electronics magazine siliconchip.com.au jumped into Polly at the right time, only for me to find that she would not start. I tried to jump-start her with a small 12V battery, only to find that she was completely drained and would not even respond to my charger. Fortunately, my very reliable battery shop was on call. I dealt with them for many years when I used to repair electric golf carts, so they came and replaced our battery, and we were still able to meet my wife’s appointment. You guessed it; the same thing happened two weeks later. There was no way both batteries were faulty. I put my clamp meter on the negative battery cable and discovered that, in standby, it showed a little over a 1A drain. No wonder the battery was flat! As it happened, Polly was due for service, so I went to the same Range Rover garage I have used for many years. I approached Service Coordinator and booked Polly in, with a request to find and fix the problem of the excessive standby battery drain. A manager listening in said, “I am not sure about helping you with such an old model, as we do not have the records or parts we may need”. I was amazed at this and replied, “if your techies cannot find a fault without the onboard computer or your old manuals, which you should have, may I suggest that they simply rig up an ammeter in series with the battery and start removing fuses until the fault is located”. There was a bit of silence, then a grunt of approval. When I returned to pick up Polly, the serviceman went through the itemised invoice before payment. There was a charge for the service, plus a separate charge stating the battery had been tested, and the technician had found that the battery terminals were loose. He had tightened them and tested the battery, noting that the drain had dropped to the normal standby drain of 20mA. I expressed disbelief at this, as I knew my battery people would not be so remiss. However, I paid up and said, “let us see what happens”. On arrival at home, I tested the standby battery drain again, and sure enough, it was still reading just over 1A! Now very annoyed, I set out to do what I had suggested to the manager. It turned out that the main interior light unit had blown the passenger side bulb, which had somehow caused a permanent tracking to Earth (probably part of an electronic switching circuit). This unit is made not to be repaired and, like all European car parts in New Zealand, is very expensive. The garage refunded the cost of the repair that did not work, and I have ordered a second-hand replacement light unit from the UK. As I had a ‘new’ one on order, I decided to open up the old one to see what had happened and whether I could fix it. I could see some discolouration on the PCB that might have been due to excessive heat. I re-soldered all the joints, and it came right, but I will still replace it. The whole board looks like it was never soldered very well in the first place! Smoothing out problems on a dot matrix printer The main interior light enclosure for the Land Rover. 102 Silicon Chip A. L. S., of Turramurra, NSW uses a dot matrix printer because he has old but helpful equipment that will only work with such devices. Not being able to buy a new one, he had no choice but to fix it when it started acting up... My ten-year-old dot matrix printer began to stop halfway through a print run, leaving only half an image. Repeating the print command occasionally produced a complete Australia's electronics magazine siliconchip.com.au image, but things slowly worsened. It began to produce a very annoying partial document, then nothing at all! My first theory was that the printing ribbon was spent because the print head was tapping away, but nothing much appeared, and when it did, the ink was slightly undercooked. I also thought the ribbon might have jammed. I ordered a couple of spares online, and when they arrived, I fitted up a new one only to be confronted by the same fault. In fact, it was worse because the printer failed to take up the ribbon’s slack and left a horrible length of floppy ink ribbon. I had to question myself: was a dot matrix printer the best option in this day and age of fancy laser and inkjet printers? Well, I use it with an Audio Precision ATS-1 audio analyser that only has a parallel printer port. I tried connecting it to various newer printers, such as an Epson laser printer with a Centronics port, but it just printed noise! Back when I first got the ATS-1 and couldn’t get it to print, I asked a friend who was very clever with these things. He immediately grabbed a brand new Epson LX300+ dot matrix printer out of his archive room, and bingo! Perfect prints! He explained that such an old analyser deserved only an old (but new-old-stock) printer and charged me only $100. Today, these dot matrix printers are still in high demand because they can handle continuous lengths of paper and carbon paper for invoices, delivery dockets etc. I was shocked to find that new ones today sometimes go for $2000 or more! So a new pre-owned printer was out of the question, and all of the pre-loved ones on eBay looked like the love affair was well and truly over. Therefore, I would have to repair mine. I did have a parallel-to-USB converter from avwidgets. com but unfortunately, it failed after I plugged it into a faulty oscilloscope (I subsequently got rid of the oscilloscope!). The converter worked but required 20 keystrokes just to print a graph, whereas the dot matrix printer required two button presses, and the hardcopy could then be scanned or photographed for storage. To give you an example, when I need to do a plot of, say, impedance vs frequency for a loudspeaker, I just attach the analyser to the speaker and then press two buttons, and it produces the graph. With another button press, a beautiful graph is printed together with the impedance value for up to 150 frequencies. This is an enormous time-saver when I need to test many different speakers. A previous contribution in the November 2021 issue documented my repair of an Epson V100 scanner. The fault seemed mechanical, but turned out to be faulty electrolytic Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column in SILICON CHIP? If so, why not send those stories in to us? It doesn’t matter what the story is about as long as it’s in some way related to the electronics or electrical industries, to computers or even to cars and similar. We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. siliconchip.com.au capacitors concealed beneath a panel, so I immediately theorised the same fault could have occurred here. The electronic control panels in the printer were also hidden from sight, so I began to split the case to get to the inner workings. The whole thing is held together with four screws, then all the panels interlock and come apart like a puzzle. Deep inside, there are two PCBs full of electrolytics. None showed any signs of leakage or swelling, and a quick test with an ohmmeter did not indicate anything drastic. My next step was to go to YouTube to see if anyone else had a similar problem. I found one guy who had a sticking Epson dot-matrix printer and described his repair in excellent step-by-step detail, but in the Telugu language, an ancient language spoken in India. He still used many English words such as “computer” and “printer ribbon” (I guess they weren’t around in ancient times), so it was still worth listening to. I could glean the rough meaning of what he was saying & doing. You can see the video for yourself at https://youtu.be/CqXDd8mAyTI Basically, he lubricated the track (which carries the printer head) with a silicone lubricant and ran it up and down by hand to ensure it ran freely. There were several other motions, like checking for problems with the cog and belt mechanisms, so I decided to check these out on my printer. Surprise surprise! The printer head was sticking ever so slightly; it felt like a mild brake was being applied at about halfway. I cleaned it up with a rag and tissues, and noticed that the lubricant had become black and sticky from dust and ink. I then used some alcohol to clean it and also cleaned the roller to remove any grease so the paper would not slip. I applied a little lubricant and decided to give it a go without replacing any electrolytics after all. Was this just a mechanical fault? Had I been influenced by my previous Epson electrolytic experience? Well, thanks to the Indian guy, it proved to be a mechanical fault. Now the printer never stops and never slips, and I vowed to treat it with loving care! SC Australia's electronics magazine June 2023  103