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SERVICEMAN'S LOG It's torture having a broken phone It isn’t often one gets to be on the other side of the servicing coin. These days, most of the time when something goes wrong, I can sort it out with the deft turn of a screwdriver or a quick touch with the soldering iron. But when you don’t have any tools handy, it's a bit hard to fix something, even if you're the world's best serviceman. If you've been following my travails in this column, you will know that I was recently staying in the Dalmatian coast of Croatia. Since then, I've driven to Munich, in Germany. The trip was very straightforward, as the wellsigned highway system is designed to carry vast amounts of traffic. I loved the high-but-safe cruising speeds, the exotic cars on display in their natural habitat and the ease of navigating through three different countries to get where we were going. I marvelled at the vast wind farms and massive solar arrays that dotted the landscape, especially through the Austrian Alps and the Bavarian countryside. siliconchip.com.au Every farmhouse we saw had almost the entire roof covered with panels, and we guessed that during winter, when the snow was deep and power supply dodgy, that they would very much come in handy. I didn’t get to see the back end of these systems, so I do not know how energy was stored or the panel output processed, but whatever was used, it was very prevalent. We also saw fields that would otherwise be sewn with wheat or hops covered instead with solar arrays, set up to track the Sun’s path across the sky. In some spots, all we could see were these solar fields and this is alternative Australia’s electronics magazine Dave Thompson* Items Covered This Month • A broken phone and a serviceman without tools • R&S CRO repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz energy on an industrial scale, a bit like the tourist industry itself in Germany. Welcome to Germany, please open your wallet On the face of it, everything there is designed to extract money from the visitor. Want to park somewhere? That costs money – even hotels and motels charge for precious parking spaces. Need a toilet break during your visit to any of the town-sized shopping malls? Better have some small change in your wallet, or you’ll be holding it in. I got the impression that if they could charge for the amount of air you breathed, they would. That aside, it is November 2018  57 a beautiful place and this trip ticked off a few of my bucket-list entries, so all was forgiven. Next time (if there is one), I’ll be hiring a faster car than the Hyundai i20 we were driving. Then again, it's well known that there is no faster car than a rental car. But as this was a brand-new car when we picked it up, it hadn’t been thrashed to within an inch of its life yet. We did around 7000km in it in the past four weeks so I’d say it is probably run-in by now! However, the trip was not without its dramas, which brings me to my point (as usual, a while coming). Shortly before we left on our Deutschland sojourn, my wife and I treated ourselves to a new mobile phone each, taking advantage of the sharp pricing available in Croatian stores. We both got a 2018 Samsung J6, a smaller phone than the Lenovo I was replacing but with a far better OLED screen, an octa-core CPU and 32 gigs of storage. They also take two SIMs, one of my buying prerequisites; having a work number and a private number in the same phone makes things a lot easier. I liked it, and from day one was snapping photos with its excellent 13-megapixel camera. I’d bought a local SIM, which would roam all over the EU without invoking the crippling charges our Antipodean telcos seem to relish in gouging from overseas travellers. It's great; travel from, say, Slovenia to Austria and literally as you go through the border, a text message informs you that you are now connected to an Austrian provider and that charges and rates will be the same as they were in your home country. Time to spend a penny So I was loving this phone. The first day in Germany, we checked into a hotel in central Munich and after wandering about the town and shopping, I went into the bathroom to wash up. My phone was in my pocket, and given the tiny size of the bathroom, it was in the way. So I put it on the glass shelf above the sink. As I washed my hands, I saw out of the corner of my eye my phone, in the sort of slow motion worthy of an action movie sequence involving the protagonist leaping away from an explosion, sliding along and off the now obviously forward-sloping shelf and straight into – you guessed it – the toilet bowl. 58 Silicon Chip With a sickening gloop and porcelain thunk, it sank into the (thankfully) clean bog water and immediately came alive, only to go dark a brief second later. Nooooooooooooooooooooooooooooo! My new phone! Only weeks in my possession! Down the toilet! I could only curse my imbecility. Panicking, I fished the phone out and tried to power it down, only for it to appear dead/non-responsive. It had only been in the water for a matter of seconds but the damage was done. About now is where I stretch the bounds of reader’s credibility; that very morning whilst shopping, we’d found an Asian foods store, something very rare in our part of Dalmatia. We bought, among many other things to create eastern-inspired meals for the family, a one-kilo bag of Jasmine-scented basmati rice. You couldn’t make this stuff up. Desperate times call for desperate measures While I soaked as much moisture from the outside of the phone as I could with a copious number of tissues, my wife located the bag of rice and tore it open. She also found an old zip-lock bag among our stuff, so I put the phone inside and filled it up with rice. I evacuated most of the air and zipped the bag up. The drama over for the moment, I could only rue the decision to put the phone on that glass shelf. I also resolved that whatever phone I ended up with next, I’d buy a proper protective case for it at the first opportunity. Not that this would prevent stupidity on my part, or even water-proof the phone, but it does seem awfully vulnerable in its naked state. While I’ve seen phones with cracked screens that had been in decent cases, at the very least, it would give me some peace of mind. The phone sat sealed in that bag of rice for the next three days, while I relied on my wife to take photos on her phone that I would have liked to save. On the morning of the fourth day, I carefully removed the phone and extracted the SIMs from it (my original and the new local SIM) and the 16GB SD card I’d transferred from my old phone. On reflection, I probably should have removed them right away but two things prevented me from doing this; firstly, all I could think about was getting the phone into the rice and secondly, this phone has a sealed back and the SIMs and SD card are seated in small plastic trays before being slipped into the side of the phone. To remove them, you need one of those pointy tools or a bent paper clip, neither of which I had on hand at the time. Once the phone was in the rice, I didn’t want to be removing it unnecessarily. I didn’t know if this rice pack would work; I’d read about it online and had seen it mentioned on police procedural TV shows. I’d even heard of clients trying it but for the life of me, I couldn’t recall whether their outcomes were successful or not. Even if it's only an urban myth, it does make sense; I suppose a bag full of the silica gel bags you get packed with everything these days would work even better but a grain of rice does have the ability to soak up a huge amount of moisture, relative to its size, so perhaps this would achieve something. It's dead, Dave But as I removed the SIMs and memory card from the phone, I could see the display showing half the charging 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. Australia’s electronics magazine siliconchip.com.au symbol and the LED flickered dimly away all by itself, telling me the phone was not happy. I, of course, tried pressing the buttons with the same underwhelming result as before; I thought the phone must have had it. Nonetheless, with great faith, I placed the phone back into the bag of rice and put it in my suitcase. There it would stay until I got back to Dalmatia and could look into repairing it. Not having the SIM popper tool was bad enough; not having any tools whatsoever with which to disassemble the phone was a form of torture. I knew if I could get into it and physically separate and dry the parts, I’d have a much better shot of getting it to work again. But getting into phones is tricky at the best of times, and I was sans tools and workshop. I know what you’re thinking; I could have found some German repair guy to open it up for me but given how expensive we found Germany, it likely wouldn’t be worth it. I recommend that clients in the same position as me make an insurance claim, as the device is likely going to have a significantly shortened lifespan even if you do manage to resurrect it. When we got back to Croatia, I put the bag out into the sun, just to sweat any further moisture from the phone. Temperatures in Germany were about half those in Croatia, with some rainy days involved, so the rice bag didn’t get very warm; maybe this would help. While it baked in the sun, I looked for a YouTube teardown video for this model phone. I couldn’t see any way to get into it except through the screen, like an iPhone, and my suspicions were confirmed by the video I found. I’d need a heat gun at the very least, and some very thin spudgers to disassemble it. Plus, I didn’t have my screwdrivers or usual workshop facilities either, a recipe for disaster given the number of screws and small bits inside the phone. Opening it up myself simply wasn't an option. A serviceman hates to give up And so for a few days, we did nothing about the phone, and when I finally removed it to test it, it was still dead. It wouldn’t power up or display anything at all and when connected to my laptop, it showed no signs of charging. Nor did the laptop recognise there was anything attached. Excellent. siliconchip.com.au There was nothing for it but to go and buy another phone and relegate this one to the scrap heap and a possible insurance claim once we got back to New Zealand. It left a bitter taste going to the same store and buying an identical phone mere weeks after buying the last one, but it had to be done. With the new phone suitably bought and configured to my liking – a story in itself – I found the SD card from the "toilet phone" was no longer working properly. It randomly dropped in and out of the system, causing alerts and notifications. While it was working, I spent ages copying the 15 or so gigabytes of magazines, saved photos and other data from it to the new phone’s internal storage. A few days after this, my Croatian brother-in-law came by for a visit and said he knew of a local guy who repaired phones and didn't charge the world, so I went to grab my toilet phone. After getting it out of the rice bag, I tried the power button, just to see what would happen. The Samsung logo flashed onto the screen and the boot process began. It seemed to be working! I had no SIMs or memory card installed but the phone booted into emergency call mode and a quick check showed everything was operational. Still suspicious, I took it over to my laptop and connected it, firstly because it only had a 5% battery charge left and secondly because I wanted to get the data off it while it was alive. And I did manage to grab all the photos and videos I’d taken in the few weeks I’d had it – which was a huge relief. My brother-in-law rang up the aforementioned repair guy and asked what he would do. He suggested leaving it for the moment, since removing the screen to access the logic boards has its own risks. He felt that (toilet) water was far less caustic than other liquids he often finds inside phones, such as beer or cola, so it might have actually escaped any lasting damage. I agreed with his suggestions. Great! Now I have two identical phones. I left the toilet phone connected to the computer until it had charged to 100% and stuck it back into the bag of rice. It can stay there for now, until I’m convinced every drop of moisture is gone. I’m reasonably certain it will live a normal life but I can’t really sell it on in good conscience, so I will hang Australia’s electronics magazine November 2018  59 The inside of the CRO shows multiple different trimpots scattered over one of the boards. onto it for spares, just in case – God forbid – I drop this new one, or otherwise ruin it. Rohde & Schwarz CRO repair M. H., of Albury, NSW, found a dual-trace cathode-ray oscilloscope that someone else had thrown away in a skip bin. While an accountant would immediately determine the cost of repair to be far beyond its potential value, he decided to try to repair it anyway... It was a fairly late model Rohde & Schwarz cathoderay tube scope with the top and bottom covers already removed, presumably because someone had a go at fixing it before giving up and chucking it out. A few blasts of compressed air removed the dirt and dust and then I took it to my workshop to try to figure out what was wrong. I rudely powered it up and jammed a 1kHz test tone into both inputs in an attempt to get a trace. Nothing appeared but I didn’t know whether it was because I simply didn’t know how to operate this unit. Maybe it was actually dead. After five minutes, eventually two traces appeared. Surprised, I continued to test some of its other functions. I found that the gain of one channel was way off. By com- On first power up, the traces settled after a long wait and calibration was OK but only on the lower volt/div settings. 60 Silicon Chip paring the inputs with my trusted Trio oscilloscope, the gain calibration of the faulty channel proved to be good until the volts per division knob was above 1mV/div and it was wrong on all of the higher settings. I wasn’t sure if it was a fault or it simply needed adjustment but with dozens of adjustable resistors and capacitors scattered everywhere on the PCB, I wasn’t convinced that I could figure out how to adjust it even if that’s all that was wrong with it. Oh dear. For any technician, sighting an adjustable pot or variable capacitor means one must immediately twiddle. If one cannot resist then at least one must immediately return any adjustment back to the original position. In this case, it was wise to resist. I had no circuit diagram or any hint of what each one did and the box was full of them. Twiddle time finished with no result. The next job was to remove the front panel to allow access to the cluster at the front where the fault was likely to be located. After removing many knobs, switches, retaining nuts and screws, the front was finally off but the fault had disappeared. Both traces were now correct and I could not reproduce the problem. So I switched it off and walked away. Mid operation: the offending variable cap is just behind the first plate of the switch with the knob still attached. Australia’s electronics magazine siliconchip.com.au ™ Next morning, I powered it up but after two minutes, there was still no trace. After an extended delay, I observed a faint hint of a trace on the top outer edge of the screen that would not be visible if the front panel was attached. The expected traces ever so slowly lowered themselves down onto the screen and eventually moved down to the (almost) correct position. But the fault in the one trace had returned. At this stage I was pretty sure that both the lack of traces initially and the incorrect position of the one trace were heat-related faults. With an SMD rework heat gun set on the lowest fan setting and with a fine nozzle, I applied heat onto a single adjustable capacitor, selected at random and close to the input connection. The faulty trace jumped instantly. Inspection of the underside of the PCB traces did not identify any dry joints on that component. I had to use a metal blade screwdriver to break the variable capacitor adjustment free and then I was able to use a plastic blade for the final adjustment. The first movements of the variable capacitor caused the trace to jump wildly. I exercised the variable capacitor back and forth until its actions on the trace become clean and linear. The driver circuit that allows adjustment of the traces up and down is located at the end of the delay line, which is a long cable coiled up in the bottom of the case. A few tweaks was all that was required to adjust the centre line correctly and this also included another variable capacitor that I needed to break free, like the last one. I then applied a frequency sweep from 100Hz to 4MHz and adjusted other variable caps at the front end to try to get a flat response. Eventually it looked good and the volts/div setting was now having the correct effect on both traces. So that I could check its power-on behaviour, I switched it off and walked away. After an hour or so, I switched it back on and the traces were immediately in the correct position. I heated the components at the end of delay line with no changes. I then heated the components at the start of the delay line and both traces moved in different directions as the board warmed up. I then decided to applied freeze spray to the components near the start of the delay line, using a tube to funnel it down to a single component at a time. Cooling any of the components had some effect on the trace. I concluded that this heat/cold sensitivity was normal and not likely to be a problem during normal operation. So I guess both problems were due to the variable capacitors all along. Exercising them may have been breaking away internal corrosion that was interfering with proper operation. The next hour was spent getting the covers back on. The scope was now working well enough considering its age. To verify this, I waited until the next morning and powered it up to find both traces in the correct position after a short warm-up period. Given how long I spent fixing it and considering how much I would have had to pay someone else to do the job, I could have easily bought a new digital scope instead. But electronics is my hobby and I enjoyed fixing it so I think it was well worthwhile. SC siliconchip.com.au DESIGN SOLUTIONS … with Battery Clips, Contacts and Holders THM and SMT Coin Cell Holders Coin Cell Retainers and Contacts Molded Case Contacts Cylindrical Battery Contacts 9V Battery Straps and Contacts Cylindrical Battery Clips and Holders IT’S WHAT’S ON THE INSIDE THAT COUNTS ® E L E C T R O N I C S C O R P. NPA PTY LTD 10 Gray Street, Kilkenny 5009, South Australia Ph: +61 8 8268-2733 • Fax: +61 8 8268-1455 www.npa.com.au November 2018  61