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SERVICEMAN'S LOG Putting the wind up an anemometer When the wind blows but the anemometer doesn’t go, it should be a breeze to fix. Actually, Dad’s entire weather station was playing up but first, I had to figure out why the batteries in his transistor radio were quickly going flat. I got a call from Dad the other day, asking if I could help him out with a couple of jobs that he can no longer do. It’s tough seeing time taking its inevitable toll and watching my oncecapable father growing old just doesn’t seem fair somehow. Once upon a time, he could repair anything and I’ll never forget the story one of his friends from his younger days told me. Apparently, they’d taken their motorbikes on an up-country run and the friend’s bike had spluttered to a stop out in the middle of nowhere. No problem for Dad; he took out his tool kit and stripped down the bike’s engine by the roadside and while his mate couldn’t recall exactly what had been wrong with it, it ran well enough after it had been re-assembled to get them home. There were other times too, like when we got stranded out in the middle of the ocean in a boat because the “V” drive failed. On that occasion, Dad jury-rigged something up so we could limp back to port. It seemed that no matter what pickle we got into, Dad could fix it. I loved that feeling of security and it was only natural I’d become a serviceman; it’s in my blood. Over the past few years, Dad has been breaking down his workshop and it’s now strangely empty. The various machines and tools have gone to either my brother or to myself but I doubt they’ll ever be used as they were in Dad’s workshop. He still has the basics though; a soldering station and other smaller tools and it was these I used recently to repair his old Panasonic workshop radio. This particular transistorised receiver has been in his workshop longer than I can remember and with its leather case and strap, it’s the epitome of the late 1960s to early 1970s style of portable radio. I well remember working in his workshop after school, listening to the latest music (and the rubbish the DJs always seemed to come out with) on this radio, so it really was part of the furniture. I doubt that anything made today would last anything near as long as this one but now it had a problem. Flat batteries A couple of months ago, Dad finally got around to putting some batteries in it after it had been sitting silent on a shelf for some years. It initially appeared to work OK but when he tried it the following day, the batteries had gone flat overnight, even though it had siliconchip.com.au Dave Thompson* Items Covered This Month • • • • Fixing a weather station Electric plunge furnace repair Kenwood TS-450S transceiver Beyonwiz DP-P2 HD PVR been switched off. Thinking he might have chosen some half-flat batteries from the pile in his battery drawer, he replaced them with some known good cells and the same thing happened; they were dead flat the following morning. Obviously, something was draining the batteries but what? Could the workshop elves be coming out and partying all night? It was up to me to find out! Years ago, in an effort to avoid going broke due to constantly buying batteries to feed this radio, Dad had installed a power socket so he could run the radio from a small plugpack supply instead. This simply involved breaking the positive line from the battery holder to the circuit board and wiring the socket so that when the plugpack supply was plugged in, the battery was disconnected. Conversely, when the plug was removed, it would run on batteries once again. Basically, the socket had to be wired this way because the batteries weren’t rechargeable types and wouldn’t take kindly to being connected across an external power supply! To be honest, I was half-expecting to open it up and find everything covered in leaked battery gunk. It’s so easy to leave batteries sitting in a device and forget all about it, only to come back years later and find it in a sorry (and usually non-working) state. I’ve done it myself, leaving many very cool and probably now highly-collectible toys and other 60s-era gadgets ruined. The goo that leaks out of old, dead batteries can be highly corrosive and it tends to attack everything it touches. Over the years, I’ve often had to tell customers who have left batteries in June 2016  57 Serr v ice Se ceman’s man’s Log – continued devices that those items were now fit only for the rubbish bin. It’s a real shame, because it’s a totally avoidable waste of good electronic gear. Anyway, when I got to the radio, I discovered that Dad and my sister had already had a go at it. Impatient, like many good servicemen, Dad had “sis” take the covers off and, acting as his eyes, have a look to see if they could determine what was going on. My sister isn’t really into electronics, so it isn’t surprising that she and Dad couldn’t find anything wrong. When it was shown to me, I was pleasantly surprised to find there were no leaked batteries; just a wire adrift from the old power socket. Dad mentioned it’d come off when they were poking around in there but that I should be able to see where it came from and take that into account when trying to find out what was going on. I removed the already-loosened case and had a good look around inside it. I could see the power socket that Dad had put in all those years ago and it was now looking very old and corrod- ed. It also looked to be a bit mangled, as if something other than a plug had been forced into it at some stage. On closer inspection, the spring-loaded contact that broke the battery circuit when the power plug was inserted appeared to have been twisted around and appeared to be shorting out across the other contacts. My guess was that it was this that was draining the batteries. Dad wasn’t interested in keeping the power socket there so I just fired up his soldering iron, de-soldered all the wires that were left on the socket and reinstated the original connections directly from the battery holder to the PCB. However, before I connected the positive lead, I put my multimeter in series with the wiring and after setting it to measure current, turned the radio on. It drew around 15mA at medium volume, which seemed reasonable to me and certainly wouldn’t drain the three Csized batteries overnight. Finally, I reconnected everything, replaced the back, switched the set on and marvelled at how much better this radio sounded than anything else I’d heard in a long time. They really don’t make them like they used to! Weather station With the radio now working, my next job involved taking a look Dad’s weather station. My parents have had this station for years; it consists of a bunch of stuff sitting at the top of a 3-metre pole rising from a deck at the front of the house and an LCD screen in a frame hanging on a wall in the lounge room. The two sections con- 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. 58  Silicon Chip nect wirelessly, the sensors on the top of the pole sending the data to the base unit which displays all the relevant information, including indoor/outdoor temperature, humidity, air pressure, wind speed and direction and rainfall. As well as showing all this weather information, the touch-screen base unit also shows the date and time. At least, it should display all that stuff but there were a few issues with Dad’s unit. For a start, the wind speed indicator showed nothing, which wasn’t surprising as the anemometer had lost most of one of the three little cups it uses to catch the wind and measure its speed. This meant that the device didn’t turn much at all, leaving a flatline display on the base unit. Several other functions were also displaying either a “0” or flat-lining, indicating that the batteries in the remote sensors were probably dead (or dying). Dad had reminded me to bring over some tools to drop the pole and so armed with a Phillips screwdriver I first removed the screws holding the supporting brackets. After carefully removing the last one, I then gently lowered the pole down before laying it on the deck in order to get to the sensor units. Before I could do anything though, I had to remove the mass of cobwebs and dead insects that seemed to fill every nook and cranny of the array. I had to be a careful though, as the plastic was almost powdery in places due to UV and weather exposure. There was nothing for it but to remove the anemometer entirely so that I could take it home and fit another cup to it. To do this, I had to undo three small machine screws and carefully release the wire from the clips holding it in place along the plastic shaft. A few of these clips literally shattered as I put pressure on them, such was the state of the framework. With that part clear, I needed to remove some of the plastic covers in order to unplug the anemometer unit. The device utilises RJ11 plugs and sockets (the same as US-style phone connectors) and these are removed by pushing a small plastic tab in on one side in order to release the plug from the socket. Once again, spider webs and the remains of their insect meals were everywhere underneath the covers, which probably wouldn’t be helping siliconchip.com.au the accuracy of some of the sensors! Indeed, some webs were so thick I literally had to push them off with the screwdriver and then pull them away with my fingers. Finally, I uncovered the battery compartment and removed the two old AAsize cells. One had started leaking a little, so they had obviously done their dash, with Dad complaining tonguein-cheek that batteries don’t last like they used to, as these had only been in service six or seven years! I gave the terminals a quick rub over to make sure there was nothing on them, then installed two new cells and replaced the battery cover. Leaving the anemometer to one side, I then hoisted the pole with one hand and attached the supporting brackets with the other. We then made our way inside and tried the base unit but, rather disappointingly, it still showed nothing. Suspecting that the problem may lie in the base unit itself, I took it down and replaced the batteries with fresh ones, even though Dad had told me that he’d recently changed them because he thought that might be why it hadn’t been displaying the data from the sensors. When I put the last new cell in and replaced the cover, most of the readings were now being displayed. The wind speed wasn’t showing up because I had removed the anemometer but the outside temperature wasn’t showing up either, so there was still a fault on the pole. Once again, I went through the process of dropping the pole and removing all the covers. I was thinking that perhaps the anemometer had to be plugged in for the outside temperature to be shown; that maybe they were on the same circuit, or something like that. I plugged the wind speed sensor back in and checked the base unit, which I’d cleverly taken with me to save my ageing serviceman’s legs from making repeated trips into and out of the house. Of course, plugging the anemometer back in had no effect on the temperature reading (but you probably already knew that) so I had to look elsewhere. I stripped the other sensors off again and cleaned all the phone-style sockets, then made sure that the various plugs had perfectly clean contacts before putting everything back together again. This time, after “rebooting” the base unit again (by removing and replacing the cells), all the figures showed up and appeared to be accurate, if the old mercury thermometer mounted outside the house was any- thing to go by. And so the pole went back up again and the base unit was placed back in its niche on the wall. That just left the wind speed sensor which I then took home with me. It’s really just a brush-motor fitted with three small hollow cups mounted at 120° intervals to catch the wind. Depending on the wind speed, the motor’s armature generates a small voltage at the output of the field and this is fed to the wireless sender via a single RJ11 connector. As mentioned, a large section of one of the cups was missing. I’m not sure how it got knocked off but going by the state of the remaining plastic, heavy rain drops could have done the job! I thought that half a ping-pong ball might make a good replacement so I fished one out of my bit’n’pieces 3D PRINTERS | TAPS & DIES | DRILLS & REAMERS LATHE & MILL TOOLS & ACCESSORIES | AIR TOOLS | FASTENERS WORK HOLDING | MEASURING & MARKING | METALS | CONSUMABLES SILVER STEEL High Hardness, Ground Finish. Available in Metric & Imperial Sizes from 1/16” & 2mm. 300mm lengths. 3mm $3.08 IDEAL FOR X1L MILLING MACHINE A small mill with a 400mm long table! Ideal drilling, slotting and face milling in your hobby space. 10mm Drilling Capacity, 12mm 4mm $3.30 DIGITAL 150MM CALIPER End Mill Capacity, 16mm Face 6mm $6.33 Zero Point, Metric/Imperial, Mill Capacity. 145mm x 330mm Table Travel. MT2 Spindle. 150W 10mm $14.03 Data Output,0.01 mm DC Motor. Call us for a Resolution. package deal! Also available: 200mm - $110 SHAFTS! 300mm - $175 $75 $689 STEAM ENGINE KITS These quality kits include all fasteners and materials, detailed drawings and instructions. Ideal for a beginner or experienced machinist alike! You will need access to a lathe and hand tools to complete this project. 20mm bore, 20mm stroke, horizontal orientation. Also available: 20/20 Twin - $350 20/20 Vertical - $170 16/16 Horizontal - $160 16/16 Vertical - $160 PROMO CODE: 09SCJUN016 OR MENTION THIS AD. PRICES INC. GST & VALID UNTIL 31-6-16. PO BOX 134 MITCHELL ACT 2911 siliconchip.com.au www.minitech.com.au $190 1300 421 553 June 2016  59 Serr v ice Se ceman’s man’s Log – continued Electric Plunge Furnace Repair A simple but puzzling fault can completely cripple a large piece of industrial equipment. D. T. of Prospect, SA recently got a large metal furnace going again with replacement parts costing less than $5.00 . . . A friend’s brother recently rang me, enquiring if I had any experience with repairing electric smelting furnaces. Apparently, they were in big trouble as no-one had been able to repair their plunge furnace and they desperately needed to get it going again. This was definitely not in my normal line of work but I’m always up for this kind of challenge. And so I offered to have a look at it and see if I could help. It was just like a massive machine monster from a horror movie! It consisted of a large crucible some two metres across which could be tipped to pour molten metal into moulds. I was fascinated to see recipe books which listed the exact mix of different scrap metals required (in carefully weighed portions) in order to produce just the type of metal needed for each project. Included in their metal stockpile were copper pipes, scrap stainless steel and even steel parts from an old bike! Three 150mm x 3m-long rods made of what looked like carbon were suspended at the ends of chains above the pot. These were in turn connected to three motors hanging from the roof. The control panel consisted of three very large current meters with full-scale readings of over 250A, press buttons to raise and lower the rods and a power on/off switch with an auto position. It was all quite daunting, even while sitting there turned off and not moving. When the power was turned on, it turned into a loud fire-breathing monster. The rods were lowered into the mix and as soon as a rod touched the mix it started arcing through the load to the crucible, causing fireworks and lots of noise. The problem quickly became apparent. As soon as an arc was struck, two of the three rods would correctly retreat and then return again to maintain the arc and thus continue heating the metal. By contrast, the third carbon rod just continued to push on into the load. At the same time, its associated current meter was pinning its needle at full scale until the whole system tripped out. I began my troubleshooting procedure by analysing how it was all meant to work. The plunge motors on the carbon rods were 3-phase 1hp (750W) types driven by three 3-phase contactors, one to activate the drawer and compared it with one of the remaining cups for size. Amazingly, it was exactly the same! The problem now was cutting the ball in half. I don’t know if you’ve ever tried it, but cutting a ping-pong ball in half is really, really difficult! I initially tried using my old Dremel Moto-Tool scroll saw but gave up after nearly taking one of my fingers off. I did manage to cut about half-way through the ball but in the interests of keeping my fingers intact, did the rest with a new blade in my scalpel. Even then it was as rough as guts but at least the ping-pong ball was now in two bits. I cleaned up one half down to the seam and then did the same with the other half, which was actually a little smaller than the first one. I then smeared epoxy resin glue over the inside of the smaller half and glued it to the larger half, making sure it lined up neatly. Once hardened, this made the ball very sturdy, and I made good use of that to rub the edge down on a piece of 400-grit wet-and-dry sandpaper. After sanding, it looked perfectly flat and I then used the same resin to glue the cup onto the remains of the previous cup. It was impossible to tape it into place while the glue set so I just sat and held it for five minutes until the glue hardened enough for me to sit it on the bench to fully cure. The finished job looked great and the overall balance of the complete assembly is good enough for this purpose. All I have to do now is put it back up the pole and that’s job done! 60  Silicon Chip Kenwood TS-450S transceiver K. G., of One Tree Hill, SA recently had a Kenwood HF amateur-band transceiver fall into his lap. The only catch was that he had to get it working before he could use it. Here’s how he went about it . . . I was recently given an amateur ra- motor and the others to swap two of the phases over to reverse the motor direction and therefore the direction of the carbon rod attached to it. Each rod and motor was supplied from the 3-phase supply via a large transformer which I estimated to be rated at around 350kVA. In addition, each carbon rod had a current sensor coil fitted to its supply to monitor the current through that rod. This obviously supplied a feedback circuit to activate the reversing function of each motor to maintain the arc from that particular carbon rod. I found that I could raise or lower the rods manually which indicated that the motors and any associated mechanical gear were OK. That meant that the fault had to be in the electronic control circuitry. This control circuitry was spread across three identical, sparsely-populated PCBs. These PCBs were so old that they were made from the now obsolete phenolic material. Unfortunately, spare PCBs were no longer available (and hadn’t been for years), while obtaining a circuit diagram was also out of the question. In order to prove that the faulty rod’s corresponding control PCB was the problem, I decided to swap it with one of the other PCBs. They were reasonably easy to unplug and remove, so I carefully labelled all the wires and swapped them over. The problem then moved to the other rod, so the fault was definitely on the control board. dio transceiver with the message that if I could get it working and make use of it, it was mine. It did not transmit and the receiver was a little “deaf”, resulting in very little audio output. The model concerned is a Kenwood TS-450S which covers the HF amateur bands from 1.8-30MHz and is rated at 100W PEP on transmit. In good working order, this model is still quite a capable transceiver, even though it is now 15-20 years old. As a result, I thought it was worth spending some time on it to see if I could fix its faults. An age of 15-20 years may seem to be quite old for electronic equipment, given that so much gear is discarded after just a few years. Some of it is now binned in less than five years even if it still working, the reason being that it has been superseded by the latest whiz-bang gizmo. However, amateur radio equipment generally has a much greater life-span than the average piece of consumer electronics. siliconchip.com.au I took both the faulty unit and a good board back to my workshop and had a closer look at the circuit. It proved to be a very basic feedback arrangement with an output much like that used to control the servo in a radio-controlled toy. I’ve fixed hundreds of these but the scale was different for this job. One advantage of being in the electronics game since the days of valve black and white TV is that you accumulate a lot of parts. The faulty board required a couple of very early transistors on the outputs to be replaced, since they had become leaky. As it turned out, I had the exact devices in stock, as they were used in some of the first solid-state portable TV sets. The two new transistors were duly fitted and I then replaced a couple of electrolytic capacitors which had high ESR readings. I then returned to the monster and refitted the two boards. I had everything crossed when the Auto button was pushed but it all worked perfectly, with the three amp meters settling down to about half-scale and remaining surprisingly stable. What’s more, the mix was reduced to liquid metal surprisingly quickly. This was definitely a diversion from my normal work but was very rewarding and interesting. I found out later that if the repair hadn’t worked, a replacement furnace would have had to have been purchased and shipped from South Africa at massive expense. With the radio set up on my testbench, I applied a 10µV signal in the 7MHz amateur band to the antenna terminals and tuned it in. Despite this strong input signal, the signal strength meter showed only quite a low reading and the audio level from the speaker was anything but strong. That said, the signal was there and was on the expected frequency. So the various local oscillators in the set were on the correct frequencies. Next, I connected the radio to a 50ohm dummy load with an RF power meter in the line. Pressing the pushto-talk lever on the microphone and whistling into the mike should have produced an output power of 50W or more but in this case, no output at all was shown on my power meter or on the radio’s internal meter. Removing the top cover revealed a large empty space where the optional automatic antenna tuner would go. There were several shielded boxes siliconchip.com.au with other parts of the transceiver in them, including (most likely) the transmitter’s 100W power amplifier. I concluded that the low-level parts in the transmitter chain were underneath. Although it was possible that the fault lay in the power amplifier, I figured that the best place to start was early in the transmit signal path. Fortunately, there was a comprehensive user manual with the radio and this included the circuit diagrams. These showed that there were separate RF and IF units in the set and these were easily identified once the bottom cover had been removed. I expected that the audio signal from the microphone would go to the IF unit first, where it is converted to 455kHz. However, when I attempted to transmit, I couldn’t detect any 455kHz signal at the output of the IF unit which was clearly labelled on the circuit as “TXIF” on pin 4 of connector W1. However, there was obviously audio coming from the microphone and there was also audio on the output pin of the microphone amplifier IC (IC15, pin 7). From there, the signal path went to a mic gain control on the front panel and then through a further amplifier to balanced modulator stage IC8. Attempts to transmit resulted in a 455kHz signal at IC8’s output, so everything was OK up to there. Following the modulator is a set of three ceramic filters with different bandwidths, each selected according to the mode of transmission. For example, the 2.4kHz filter would normally be selected for SSB mode. The selection is done by diode switches and one of the switched DC voltages which controls the diodes is called “TXB” which I measured at a shade under 8V at the input to the IF unit on pin 4 of CN1. I then looked for the TXB voltage on diodes D11 & D12 but the swing from receive to transmit was nowhere near what I had expected. Next, I looked for the TXB voltage on pin 4 of CN5 but it was way below the 8V measured previously on CN1, even though the two connector pins are supposed to be directly connected together. Now we were getting somewhere. Measuring the resistance between the two connector pins resulted in a reading in the kilohms region. It was time to remove the IF PCB completely for a close examination and that simply involved undoing five or six screws and unplugging all the connectors. Once it was out, I put my multimeter probes on the two connector pins for another check and got the same high reading as before. As an aside, I had recently bought a pair of multimeter probes with needle-sharp gold-plated points. They’re just the shot for probing small pads and tracks on PCBs and for poking through tarnished leads and solder to get a good connection. I followed the track from one connector pin to the other and soon found the discontinuity at a small via. I then noticed some black “gunk” on the board which I realised had come from a nearby large electrolytic capacitor. On checking the circuit again, I discovered that this capacitor coupled signal from the audio power amplifier to the loudspeaker. I checked this capacitor using my trusty ESR meter and found that the ESR was about 80Ω when it should have been just a small fraction of an ohm. No wonder the audio output level was low on receive. I replaced the faulty capacitor with a new one and cleaned off as much of the gunk as I could with isopropyl alcohol (IPA). It was then necessary to link the two connector pins with a thin wire to restore continuity. With the PCB back in place in the chassis and all connectors replaced, I then tried the transmitter again and was delighted to find that it now worked. After making a few adjustments, I found that I could measure 120W peak at the output. June 2016  61 Serr v ice Se ceman’s man’s Log – continued Beyonwiz HD PVR Repair Regular contributor B. P. of Dundathu, Qld likes to rescue and repair non-working PVRs that are advertised on eBay. He bought this one for a song and repaired it using parts on hand . . . I recently noticed a Beyonwiz DP-P2 HD PVR listed on eBay as not working or for parts. The auction had a few days to run, with several bids already, so I kept an eye on it. As the auction neared the end, I placed a bid, which I considered a fair price for a non-working unit. I’ve repaired a few Beyonwiz PVRs in the past, so I thought I would take a chance on this one as it was a top model in the Beyonwiz range at the time. I won the auction and the unit arrived in the mail a few days later. To initially test it, I plugged it into the power and fired it up and sure enough, it stopped with “Error 0000” indicated on the display. I then unplugged it and took the lid off. I hadn’t heard the 500GB HDD running when I’d first turned it on, so I unplugged the drive cables, reconnected them and fired the unit up again. It still came up showing “Error 0000” but I could now hear the HDD running. However, it was very quiet, which explained why I couldn’t hear it with the lid on. Things weren’t quite so rosy on receive though. Certainly, the audio output had improved and the sensitivity was better but it still wasn’t up to scratch. The receiver’s internal noise could be heard and in addition, there was a faint but noticeable crackling in the audio with no input to the radio. Unplugging the RXIF input to the IF unit at connector W1 gave a drop in the noise but the crackling remained. An IF gain trimpot is positioned halfway along the IF amplifier chain and turning this right down reduced the noise and crackling to zero. That meant that the problem lay somewhere between the input to the IF board and the trimpot. To track this fault down, I first connected a 100nF capacitor across the output of the first IF amplifier just prior to the ceramic filters. The idea here was that this would act as a short circuit for the IF signal. The crackling remained, so that meant that the fault 62  Silicon Chip I then noticed some muck on one of the larger electrolytic capacitors on the power supply board. A closer look indicated that the capacitor had “erupted” and I then noticed that an identical one nearby was slightly bulging at the top. I whipped out my soldering iron and allowed it to heat up while I removed the power supply board. The two faulty capacitors were both 3300µF 10V types and these were quickly replaced and the power supply board refitted. I fired the unit up again and the “Error 0000” message had now cleared. In its place was a TV channel indicator on the front panel, so I connected the unit via an AV cable to a small TV set but I couldn’t get a picture, despite pressing the TV-OUT button on the remote to change the video output several times. I didn’t have a spare monitor or portable TV with an HDMI input, so I took the unit into my lounge room and hooked it up to our main TV set. I then got a picture and after connecting the antenna, I was able to tune in all the local channels. A quick flick through all the channels indicated that everything was working well, at least as far as TV reception was concerned. Next, I checked the recordings on the was likely to be in the vicinity of the ceramic filters. Just to be sure, I then placed the 100nF capacitor across the output of the ceramic filters and the crackling disappeared. I then remembered a similar problem that I had encountered in the past, when leaking electrolyte from a faulty capacitor had caused just the sort of crackling I was hearing. What’s more, the ceramic filters in the set I was working on were adjacent to the leaking capacitor I had replaced earlier and it was quite possible that some of the goo had spread out under one or more of them. That meant that all three filters had to come out so that the board could be properly inspected. Removing them from the closely packed board was a bit of a challenge to say the least. Two of them were small black rectangular blocks with five pins, while the third was a much larger device with a pair of pins at each end and a ground pin for the metal case. HDD and found that the oldest recording took place 24/8/11, while the most recent one was on 10/11/12. This indicated that the unit had been used for over a year but had not been used to make any recordings for the past three years. So was the unit able to record properly? It was time to find out. I set it up to record a program for that evening and all worked correctly. So the power supply had apparently failed in its first year of use. In view of that, it’s likely that the unit had been used in a poorly ventilated area (possibly enclosed in a cabinet), which caused the power supply to run hot and the capacitors to fail. All the other capacitors were still good but the two that had failed looked like a cheaper brand than the others, so they were probably doomed to fail anyway. I used two recycled Nichicon capacitors to replace the two faulty ones, so the unit should now have a new lease on life. It will eventually be used in our family room but I will need to find a monitor or TV that has an HDMI input, because it may not work on AV on our current TV, although I can test that later. In fact, it could well be the AV input on our small TV that isn’t working and I’ll check that when I get time. And so another piece of useful (and still reasonably modern) piece of equipment was saved from the scrap heap. The best part was that it cost nothing to repair it, since I used recycled parts. Eventually, I was able to remove the three filters without damage to the board and wasn’t surprised to see that some of the black goo had spread under the filter closest to the electro. Some more cleaning with IPA ensued, followed by a blow-off with compressed air. The filters were then reinstalled and the board put back into the chassis. Powering up the radio now resulted in just the expected noise from the speaker without any of the crackling. So I’d nailed it! A quick check with a signal generator set to 50µV showed that the receiver’s gain was now back to what was expected. While I was at it, I adjusted the signal strength meter to read S9. This is the standard setting for a 50µV signal at the antenna terminals for HF amateur radio receivers. The old Kenwood TS-450S transceiver now works well and is a useful addition for contacts on the HF amaSC teur bands. siliconchip.com.au