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SERVICEMAN'S LOG I hope the purists won’t spit their dummies Dave Thompson I love a good restoration; it’s great when old gear is kept working into the 21st century in original condition. But sometimes that just isn’t possible, and it’s a good enough result to get something working again while keeping it looking original. So what did I do that will get certain knickers in a twist? Read on to find out... As I mentioned last month, all these lockdowns are (generally) bad for business, but they do give us time to do those jobs that were waiting for the shipment of round tuits to arrive. One of these jobs is a 1940s Gulbransen valve radio a friend had given me a while ago to check over. It has been sitting in a corner of my workshop gathering dust for a while, simply because it looked like a huge mountain to climb. This is one of those large mantel radios with an oak-veneered timber case. It has a gently-glowing dial displaying 46 Silicon Chip the many short and long-wave bands available at the time, a nifty ‘magic-eye’ tuning indicator and a sizeable built-in speaker, all giving it a typically warm valve radio sound and aesthetic. The problem with this radio is it had been stored in an outside shed for the last 40 years, and the moisture has really gotten into it. The timber finish has cracked, faded and lifted in places, and the fawn-coloured grille-cloth and paper speaker cone now almost Australia’s electronics magazine Items Covered This Month • • • • The week old vintage The self-made (repair)man Yamaha E303 keyboard repair Peak Instruments component analyser repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz siliconchip.com.au non-existent (possibly due to rodents or other critters chewing on them). Worse still, the metal chassis and internals are so corroded they are – in my opinion anyway – beyond reasonable repair. The guys from the Vintage Radio section of this magazine will likely scoff at this assessment. It seems that anything is restorable and/or worth restoring to them! I’m imagining them right in their beautiful, wood-panelled office with Venetian blinds, stippled-glass windows, walls of filing cabinets and not a computer screen in sight, scoffing away. But keep in mind that I’m new to this vintage stuff, and I don’t want to start a job that I can’t finish! For me, the problems arise when I quote to the customer the huge amount (including many labour hours) it would take for me to restore this radio to health. Someone – a specialist restorer perhaps – might be able to do it less-expensively, and I put this to him as an option. He (rightly) had a minor coronary when I told him how much I would charge, and told me in no uncertain terms it simply isn’t worth that kind of money to him. I surmised as much, as I’ve been down this road many times before. People assume it’s just a lick of paint, a few lines of code, or the push of a button that fixes their prized possession; but we know it’s much more involved. That said, he did say this radio was owned by a favourite relative whom he used to visit as a child, and so it has much sentimental value. It would also be great to get it going again. So what could I do? Unless someone really wanted to put the time and love (and money) into this radio, I wouldn’t consider it a viable restoration project. For one, Collier and Beale (made locally under license from Gulbransen and distributed by HW Clarke) likely made many hundreds, if not thousands, of this radio model back in the 1940s. So it probably isn’t all that special, aside from the obvious sentimental value to my client. By now, I imagine dedicated restorers/collectors are frothing at the mouth at what I’m saying. But I suspect the vast majority of these have ended up in refuse tips all over the country. The tuning gang is seized, the valves have simply gone, and the chassis is siliconchip.com.au so rusted it would need stripping and mechanical restoration, I’m just not up for it; at least, not without being paid handsomely. Consider that the wiring, the valve sockets and every other electronic component would likely need replacing. While I have a reasonably extensive collection of new, old stock (NOS) and salvaged parts from old valve and early transistor radios and amplifiers, I just don’t have what this radio needs. So I’d need to spend time sourcing and purchasing those parts before I could even get stuck into the restoration. The woodwork wouldn’t be a problem for me, given my proclivity for working with timber, and I suppose the metalwork restoration wouldn’t be too onerous either when it comes down to it. But if the customer doesn’t want to spend the money, what am I supposed to do? Sadly, working for the sheer love of it doesn’t pay the bills, and I just can’t do that these days. The customer then came up with the idea of replacing the guts with modern components, keeping the radio’s outward aesthetic but using the likes of modern amplifiers and tuners. He asked me if it would be possible to combine modules that he’d seen advertised on eBay and AliExpress to do this, and I agreed it should work, and would cost a lot less than a full restoration job. He was OK with this option, so I did some research and ordered some inexpensive modules and a suitable speaker from our Chinese friends. While I waited for them to arrive, I set about tidying up the cabinet. I will be keeping everything I remove (the chassis etc) in its original condition, just in case the customer wants to do a complete restoration later. I won’t be altering anything externally to maintain the radio’s authentic look, other than to re-finish the timber bits and pieces. I only say this to deflect any blowback I’ll be getting from the vintage radio mafia! Gutting it and cleaning it up The first thing I had to do was remove everything from the case. This involved just a few screws and unplugging a few interconnecting wires. Obviously, I was very careful in keeping the integrity of the original parts, but in the end, I needed to get it all out so I could work on the case. Veneer is a tricky material. It looks Australia’s electronics magazine April 2021  47 fantastic, but is just a hyper-thin layer of some more-expensive timber laminated (glued) onto a cheaper timber underneath. Better-quality radios and stereograms were made out of solid, furniture-grade timbers like oak, walnut and elm. But sadly, not this one. Veneer is usually so thin that any damage to it, such as a hole worn through it, renders the rest of it pretty useless. Patching it often looks awful, unless you are very skilled, know what you are doing and have a selection of similar veneers on-hand. I am not skilled at veneer repairs, don’t know what I’m doing and don’t have any suitable materials on-hand, so that’s three strikes and out for me. Fortunately, in/on this case, the veneer had simply lifted and cracked a little here and there, most likely due to moisture dissolving the glue that held it down in the first place. So I thought that it might not be too challenging to repair. There was the odd chip, probably where something had fallen onto the radio while it was stored in the shed, but these dings were all small. So I thought I’d be able to get away with merely soaking and re-gluing the veneer down, sanding it all lightly and then re-oiling the whole thing with Danish oil. It actually turned out quite well, given the age and damage and my lack of skills in this area, and once it was oiled and I applied a couple of clear coats of lacquer, it looked very nice and still maintained a realistic vintage vibe. The other problem that I had to solve was the dial glass. The magic-eye tuning indicator is mounted in the middle of it, and it is connected to the rest of the old electronics via a flying lead/valve socket arrangement. The glass was quite dirty, and many of the screen-printed station markings were a bit worse for wear. I was unsure how to clean it without damaging it further. I started with soap and water, then progressed to methylated spirits with a very careful application in one hidden corner to make sure it wouldn’t wipe the whole thing totally clean. The outside surface was no problem; just soap and water cleaned off all the accumulated dust and grime quite well. I managed to remove most of the dirt from the inside – the printed side – without damaging any more of the station information. We’d not be using any of it now anyway, but I wanted to retain the radio’s original look. Now for the fun bit The modules and speaker I ordered arrived not long after finishing the case. I purchased an 8W amplifier module, an FM tuner module and a Bluetooth receiver that could be connected to a smartphone, complete with a small remote control. Grand total: $29. You just couldn’t make any of this hardware for the money. The speaker I bought is a 5-inch, 20W multi-range model that would happily handle anything the amp would throw at it, for just $11. The most expensive part I had to buy was the replacement grille cloth. While there were more modern-looking cloths available, I wanted a traditional look, so I had to buy a square meter of it, expecting to use just a third of that. No matter; what I don’t use will go in my parts bins for another project. Fitting all this gubbins into the case was the next challenge. Once I removed the chassis, there was nothing left to mount anything on. And I still needed to sort out a light to shine through the old dial gauge to give the appearance of a soft-glowing bulb. First, I needed to mount the new speaker, which had a completely different footprint from the old one. I made up a thin, custom timber insert with the correctly-sized hole cut into it, and tacked it directly to the old speaker-mounting facia. I then removed the old grille cloth, squeezed the new one in around the sides, and stapled it after pulling it taut. It looked almost original, and I was quite pleased with it. Next, I’d need a power supply for everything. The modules required ei- Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column? If so, why not send those stories in to us? We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. 48 Silicon Chip Australia’s electronics magazine ther 5V or 12V, so it wouldn’t be too difficult. I thought about purchasing a power supply module at the same time as the others, but fortunately, I’d already bought a suitable one a few years ago for another project and had never used it. It would do nicely here. The only extra component to add was a power transformer, and as I have about 200 of the things lying around after buying a transformer-winding machine a while back, it didn’t take me long to find one to do the job. The amplifier would require the most power, with the Bluetooth module and tuner lapping up the remainder. I mounted the transformer directly to the bottom of the timber case with a couple of wood screws. Inter-wiring was done using standard light-gauge cables, routed and tied-wrapped into place. The mains lead was simply clamped into place (to proper specifications) and run directly out from the back of the box. The FM antenna was routed around the inside of the case. Our FM reception here is generally OK, so this ad-hoc aerial should suffice. I used stand-offs and long screws to mount the other modules to the inside sides of the case close to where they needed to be. They all use terminal blocks for interconnections which made things simple, and P-clamps and cable ties kept everything looking nice and neat. Tuning was the next challenge. The various FM modules available online are tuned with either a remote control, a manual up/down push-button or rotary tuning using a potentiometer. Many of these modules come with comprehensive LED displays, none of which my customer was keen on. A vintage-looking radio with an LED display chopped into the front isn’t that appealing. We decided that, since he usually tuned into a single station, he would forgo any gaudy displays and just manually tune it, hopefully using something resembling the original knob, if possible. Volume control was similarly problematic; many of the modules used a digital volume adjustment system. But in choosing an amplifier module that used an old-fashioned pot, that made my job much easier. All I had to do was remove the pot from the module and, using suitable flying leads, connect it via an adaptor to the case where the original volume pot used to be. siliconchip.com.au Our capabilities CNC Machining UV Colour Printing Enclosure Customisation Cable Assembly *** Box Build *** System Assembly Ampec Technologies Pty Ltd Australia’s electronics electronics magazine magazine Australia’s siliconchip.com.au Tel: (02) 8741 5000 Email: sales<at>ampec.com.au Web: www.ampec.com.au April 2021 2021  49 FEBRUARY 37 The original knob obviously wouldn’t fit the new pot, so I turned up a simple brass adapter so it could fit onto the much smaller shaft of the new volume control. I did the same thing with the ‘tuning’ pot, and a new rotary on/off switch that mimicked the originals. It actually all ended up looking very stock-standard, and the customer was happy with how it presented. A bit of solder here and there had the speaker and other ancillaries connected up, and it was ready to test. It worked very well, especially as he is a ‘set-and-forget’ user. The only thing left was the dark dial. Obviously, I couldn’t tee up the new tuning with the old manual dial-cord system or magic-eye, but he wasn’t worried about that. What would make a difference is the glow from the old dial. To this end, I simply rigged up a couple of orange LEDs and, after a bit of experimentation, adjusted the series resistors to provide a convincing soft glow. I could have gone for blue or something a bit more modern, but instead tried to maintain the vintage look of the original radio. All in all, it ended up looking OK and working very well, and as a bonus, he can stream music from his phone if he desires. The sound is excellent and the volume punchy, so all in all, it was a good solution to the problem. Another happy camper! The self-made (repair)man S. G. of Mildura, Vic had a frustrating time chasing a fault which seemingly he had caused, but he still can’t figure out how... You might laugh at my story, but you wouldn’t if it happened to you! I just spent over a week trying to repair one of my stuff-ups. A couple of weeks ago, I purchased an amateur band radio for the 2m and 70cm bands. This was going to replace the 2m radio that I had in the back of my Pajero ever since I first got my license. It also involved installing a new antenna on the bullbar, where the old UHF CB antenna used to live. I moved the UHF antenna to the side of the bonnet and mounted it with a special Z bracket, so the bonnet will still close. This works fine, and so does the new VHF/UHF antenna for the new radio. The only thing that I had left to do was to drill a hole in the firewall, right next to the cable feeding 12V to the caravan. 50 Silicon Chip This cable is also used to supply a 6-way fuse block so I can run fridges from the auxiliary battery, as well as the CB radio and the new amateur band radio. I used a 25mm hole saw and a short length of 25mm flexible conduit to act as a gland through the firewall. I took care in drilling the new hole, as there are several wires in the area that go off in all directions on the inside of the firewall. Yes, I did check before drilling the hole, but still managed to take out the interior lights, the digital clock and the hazard and turn indicators! First, I decided to check the fuse. The Pajero has two fuse boxes, with one in the engine compartment that houses the fuse for the hazard lights. The second fuse block is under the dash and requires removing the trim piece around the steering column just to gain access. The clock and interior lights are both on the same fuse, and I fixed them by replacing the fuse. The hazards are fed from two power sources, one permanent power (from the fuse block in the engine compartment) and the other is the accessories circuit fuse block under the dash. This is so that the hazards will work independently of the ignition key. Pressing the hazard button changes over the power feed from accessories to permanent power. This hazard switch also links both the right and the left blinker circuits so that all the lights flash at once. After more head scratching, I checked more fuses. I pulled the Australia’s electronics magazine blinker fuse (not easy due to the poor access) but it appeared OK. Next on the list was the blinker can itself. The only way I could think of to check whether it was faulty was to try replacing it. I then had the idea to bypass the blinker can, which involved fitting a small link wire between the B and the L pins on the socket. I now had all of the hazard lights and blinker lights working. At this point, it looked like I would have to pull the whole dash apart just to gain access to the wiring loom. I took out the gauges, speedo and tacho cluster, just to see if I could find any damaged wiring, but it was impossible to see properly behind the dash. I even tried to feel for damage to the wiring back there, but if I found it, how would I repair it? It looked like the Pajero was built around the wiring loom! After some further checking of the blinker can, though, I struck gold. This was a three-pin can (some have just two pins), and on checking the can in my workshop, I determined that the third pin was a ground and was needed as it is an electronic type and has a constant flash rate, independent of the lamps. Tracing around the blinker can socket, I soon found that while power was present, there was no ground return. I ended up cutting the ground wire from the socket, soldering on a new ground wire and attaching it to the chassis. It still didn’t work, so I called it a day. On Monday morning, I popped into a local shop and bought a new can. siliconchip.com.au After fitting it, my hazards and blinders worked – I breathed a sigh of relief! I don’t know how the blinker can failed; there is not much in it in terms of electronics. It just looks like a 555 timer driving a small relay. Anyway, I don’t care, it all works now! Yamaha E303 keyboard repair J. K. of Castlecrag, NSW spent a long time tracking down a problem in his keyboard, but at least the fix cost virtually nothing once he had diagnosed the fault... I purchased a Yamaha E303 electronic keyboard about 10 years ago, siliconchip.com.au second-hand, for about $300. It is an excellent learning tool, and had been enjoyed by my grandchildren almost every time they visit. A few years ago, the highest note (high C) stopped sounding. Since I seldom used it, I didn’t do anything about it. Actually, that key plays an important role in one of the resets, but I did not need it for that purpose. In the last couple of months, several more keys stopped sounding. I jumped online and found the service manual, but it did no more than show how to disassemble the unit. Disassembly is fairly intuitive, but Australia’s electronics magazine removing the keys to expose the pressure pads was not obvious. Luckily, the manual provided some pictures which showed how to do it. There are 61 keys in total. Each is sounded by two carbon sticks contacting the pads on the keyboard, completing a circuit. The E303 is a touch-sensitive piano, so the harder the key is pressed, the louder the note. This happens because of the resistance of the carbon sticks on the pads changes with pressure. A very common problem is dirt on the pads or the carbon sticks. Spilling coffee or sticky drinks on the keyboard April 2021  51 will cause significant problems, but cleaning the carbon sticks and the pads (with isopropyl alcohol) did not help. So I had to check that the connections between the keyboard and the control unit were solid. That is a very tedious job which required tracing voltages through the connecting sockets and onto the keyboard. The control unit (DMLCD in the service manual) provides 3.3V to the two keyboard circuit boards 61L and 61H via multi-cable leads 1 and 2 (see the accompanying diagram). I traced the +3.3V DC supplied to CN831 on the DMLCD board, at pins 1, 4, 5, 8, 9, & 12. The 3.3V supply is referenced to Earth as it appears on the control boards, but there is no cable carrying the Earth connection. Instead, pin 7 of CN833 is about -0.2V referenced to Earth and that translates to +3.095V on each of the pins mentioned above. All the voltages were present and correct. I had hoped that the service manual or Yamaha themselves would give me some leads, but they stated that they do not get involved in repairs, and refer all such enquires to their “Service Agents”. Strangely, the Service Agent for the Sydney area is located beyond Windsor. Each pad serving a note consists of two contacts which are “connected” by the carbon sticks when a key is depressed. Each contact on the circuit board connects through a diode to other pads, then connects to the control unit. Its a very clever system, because just twelve or so leads convey information about which of 61 keys has been pressed and whether two or more keys are involved. The diagram shown on the previous page is part of the left-hand keyboard circuit board 61L. The squiggly lines are the contact pads, two for each note. So it became a job of tracing all of the 122 diode connections back to the control board. That’s when I found five copper tracks with no continuity. Some kind of corrosion or stress had broken the links. The tracks are very fragile, so even a small amount of corrosion could break them. I considered spraying the boards with a conformal coating, but the risk of some spray getting on to the contact pads discouraged that idea. If more connections break in future, I will know what to do. Luckily, the fix was relatively easy; I just soldered a short length of wire 52 Silicon Chip between each of the diodes with a failed connection. After doing that for the five tracks, all of the failed keys came to life! I expect that a very experienced technician would recognise the problem quickly and would simply replace the two (low and high) keyboard PCBs, 61L and 61H, with a component cost of about $100 plus the time of swapping the new boards in. Doing what I did – tracing the problem – took about 30 hours which would have cost about $2000-3000 at standard labour rates. Which is why, these days, most repairs are not made at the component level, and instead, the boards are simply swapped. I think the control board for this keyboard costs about $350 – more than I paid for the whole thing! Repairing the Peak of test instruments P. B. of Kaitaia, New Zealand had given up trying to repair a piece of test equipment, but then when he went to take another look, a solution presented itself... I am a retired service technician. Some 20 years ago, I decided that a Peak semiconductor component analyser would greatly assist my servicing work despite its relatively high price. I took extra care to ensure that I did not connect it to any live equipment, and that any capacitors were discharged before using it. At some stage in its life, the self-analysis check it does on startup came up with a fault code. Sadly, Australia’s electronics magazine the user manual gives no information on what the codes signify. Looking at Peak’s site, I rapidly concluded that returning it to the UK for service would cost more than purchasing a new one. Dave Thompson recently mentioned his Peak instrument in a Serviceman’s Log column (March 2021; siliconchip. com.au/Article/14784), which jogged my memory. I decided to have a look at it again and started by replacing the battery. However, as I went to remove the battery, I became aware of what seemed to be a dry joint where the negative battery spring terminated on the board. It looked dull grey and pitted. Ancient memory then stirred into life, of a discussion with a serviceman in the area some years back, of a similar fault of another piece of batterypowered equipment where the negative wire had dropped off. The consensus was that it was a common occurrence on aging batterypowered equipment, only affecting the negative terminal. Sure enough, a hot soldering iron and a shiny solder joint later, the analyser sprang into normal operation. I wonder if this is a form of electrolysis. Three different metals are in contact: the plating on the battery spring clip, the copper PCB track and the solder. With the passage of time and current passing through it, the solder joint deteriorated. The voltage drop was not enough to stop the self-analysis or the display working, but it was sufficient SC to trigger the fault code. siliconchip.com.au