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SERVICEMAN'S LOG Instant servicing: no such thing Customers who demand instant, while-youwait service can make life hard for everybody – including themselves eventually. On the other hand, customers who are confused by modern VCRs and similar systems have a genuine gripe. It’s about time we had some really easy-to-use devices. John Carter runs a security firm just down the road from my workshop, selling and installing alarm systems. One day, some time ago, he brought in a Mintron MTV-3001CB CCD colour camera and asked if I fixed these things. I told him that I’d stopped fixing them a few years ago, when the circuits and the mechanics became almost too small to see with the naked eye. John pointed out that this camera was fairly ancient but he couldn’t find the service agency for it. In view of that, he asked if I would give it a go. Eventually, I agreed to give it 15 minutes when I wasn’t busy and, if I wasn’t getting anywhere, I’d let him know. In due course I removed the metal covers and found that the camera was split into several modules: one for the actual CCD camera, one where the output sockets were mounted, and three Fig.1: the relevant section of the Sony KV-F29SZ2. Transistor Q604 is at centre left, while voltage regulator IC303 is at top centre. The OFF MUTE connections are at lower right. horizontal boards stacked neatly one above the other next to a metal can. First, I checked the +12V rail at the input to a 3-pin IC regulator and confirmed that there was 5V coming out. I tapped it, heated and froze it but otherwise it was completely dead. Next, I tried to find the service agency but I had no luck eith­er, which meant that the circuit wasn’t available. I didn’t bother to venture inside the sealed metal can as I had no idea what it did. Anyway, I had given it my best shot and reassembled it to give it back to John. When he called, I told him I couldn’t fix it economically. He said that the camera was no good to him and told me I could keep it for spares. I thanked him and put it aside. Months passed and after being burgled, I decided to upgrade my security system. I had already obtained a time lapse video recorder but what I really needed now was a camera. That’s when I remembered John’s Mintron and thought I would give it a few hours of my own time at weekends (talk about a busman’s holiday). Anyway, I reopened the camera and examined each board assembly very carefully. I also unsoldered and removed the covers of the metal can and had a good look round. By and large, the soldering was quite good and some boards used double-sided print­ed circuit patterns. Finally, with all the covers off, I connect­ ed the camera to a monitor and power supply and switch­ed on. Once again I tried tapping, heating and freezing, desperately trying to coax some life into it. And then, having unsoldered the screening can, I sprayed freezer onto a little board inside and to my excitement a picture suddenly appeared on the monitor in full colour. Well, the problem seemed to be in this area but what could it be? I tried heating to reconstruct the fault but the picture was still there. Tapping it didn’t make any difference either. MARCH 1999  19 In fact, I couldn’t fault it at all. I examined it carefully and, on second thought, felt perhaps the soldering could be reworked – maybe there was an invisible hairline fracture though I really couldn’t see anything that was cause for concern. After soak testing it for an hour I decided that it had fixed itself. On reflection, that was a ridiculous hope – on a par with winning the big one! I reassembled it completely and switched it on. You’ve guessed it – the picture had gone again. I disassembled it once again and repeated the freezing treatment as before. Once again, the picture returned. This time, I’d tried to be very careful where I sprayed the freezer but it still hit an area of at least six square centimetres. Unfortunately, because the covers were metal, it was too risky trying to reassemble it while it was switched on. Instead, I did the next best thing – I reassembled it a step at a time until the picture disappeared, which was just after resoldering the metal screen covers to the small module. I unsoldered them again but still couldn’t find out what was causing the trouble. Next, I reworked all the solder joints – again without suc­cess. However, when I moved a blue lead on 20  Silicon Chip the screen side of the double-sided PC board, I noticed that some if the component pigtails had pierced the plastic insulation and so were shorting to the inner conductor when the metal screen was in place. All I had to do was re-route the cable, clear of the pigtails, to execute a complete repair. Although the cause of the problem was simple, it took a long time and a lot of trial and error, with a few red herrings, before it was eventually tracked down. Initially, John wanted it back but the repair cost was higher than he was prepared to pay and, in the end, he was quite happy to let me keep the now work­ing camera. Quick fix wanted Mrs Evans wanted a quick service call on her TV set, a Sony KV-F29SZ2 (G3F chassis). Unfortunately, I couldn’t oblige as I was snowed under with work at the time, even though the no-sound fault sounded simple. Instead, I had to insist that she arrange for her husband to deliver the set to the workshop. As a sweeten­er, I offered to lend her a portable set while it was being fixed and so we struck a deal. When it was delivered, she added that the width was also intermittently distorting. My decision to tackle it in the work­shop instead of the customer’s home had been the correct one. On checking the picture, there was obvious intermittent east/west pincushion correction. Apparently, the fault had oc­curred when a little girl had been turning the set on and off repeatedly. I was hoping that there was a common part that connected these two seemingly unrelated faults. I started by examining the sound circuits, suspecting that a common voltage rail had failed that was shared by the sound and east/west correction circuits. However, there was 9V, 12V and 30V to the sound circuit, which was correct. Having checked the supply voltages, I tried running my fingers over IC202 and IC203 but this didn’t produce any sound in the speakers either. I had to have the set face down on its front to get access to the underside of mother­boards A and D to do this – another good reason to have it in the workshop! Next, I connected an audio probe (a small battery-powered transistor amplifier) and found that sound was reaching pins 19 (R OUT) and 20 (L OUT) of IC202 (TA8776N) but not pins 2 & 4) of IC203. Between these points are two muting transistors, Q209 and Q210, and I found that shorting pin 1 of the “OFF MUTE” connector (CN108) to chassis restored the sound. I followed the lead back to pin 1 (OFF MUTE) of connector CN0528 on the D board and then to the power supply and the col­lector of transistor Q604 (2SA1309A). This PNP transistor has its base connected to a 15V rail (pins 2 & 3 of connector CN117) and this rail also supplies IC303, a 5-pin voltage regulator. As I quickly discovered, there was roughly 12V on Q604’s collector. However, when I shorted its base to its emitter, this voltage would collapse (ie, the transistor would turn off) and the sound would recover. The abovementioned regulator (IC303) provided a 12V rail at its output and this was fed to the emitter of Q604. But the best news was that this same 12V source also fed the pincushion con­trol IC2504. And the output from IC303 wasn’t exactly 12V but was slightly lower. It was also varying, thus switching on Q604 in the muting circuit. Replacing the IC fixed both prob- Fig.2: the switchmode power supply from the Sony KV-G21S1 (G21S11). IC601 is at left, transformer T601 (black) is at centre, and IC602 at lower right. lems simultaneously, and the customer was happily reunited with her set after it had been soak tested for a week. An arrogant customer The major drama this month was undoubtedly Mr Sutherland’s (no, not his real name) Sony KV-G21S1 TV set. Initially, he wanted me to call and fix it in his home after a power surge had killed it. Well, I nearly did and probably would have if his attitude had been less demanding and arrogant. When he rang, he demanded that I call immediately and was really quite abrupt and rude. He obviously thought that I had nothing better to do but wait by the phone, ready to drop everything the instant he called. When I told him I couldn’t call right away, he told me that he thought I was an overpaid idiot. And he said that he was going to get someone else to do the job who was “quicker, cheaper and undoubtedly more intelligent”. Not that that bothered me – I’d rather not deal with petulant customers. That was three months ago. I thought I’d heard the last of the matter but then, earli­ er this week, a much chastened Mr Sutherland (please call me Peter) turned up clutching his KV-G21S1. It was covered with tickets from at least three other service centres. Apparently, he had been hawking his set halfway round the world, trying to get it fixed quickly, cheaply and (presumably) more intelligently by someone else. Finally, he had collected the set from the last of those centres after his patience (if he ever had any) had run out. Anyway, please, please could I fix it? Not wanting to show my obvious pleasure at his supreme discomfort, I humbly booked it in with the pride and dignity befitting my lowly station in life. Ahem! Well, I may have won the battle but I certainly hadn’t won the war. The set was dead, despite having high voltage reaching pin 1 of IC601 STR-S6707. This pin is the collector of the internal chopper transistor in the power supply. It couldn’t even raise a “chirrup” on start up and, apparently, wasn’t even trying to oscillate. A quick examination revealed that a lot of work had been done around transformer T601, judging by the amount of fresh soldering. Someone had been trying all sorts of components, not all of them original manufacturer’s replacements. I knew this wasn’t going to be a straightforward job and I felt I needed to have an edge of some kind. I didn’t want to waste lots of time and money ordering spare parts that might not fix the problem. Fortunately, I am on good terms with our local Sony service agent and it was just lucky that a similar set, a KV-G21S11 (note that type number) which had been dropped, had just come in. The tube and cabinet had been smashed but the motherboard was OK. They had already scrounged a few parts from it but, provided these were replaced, they still considered it a “goer”. This was great. I now had all the parts to hand I could possibly need. The only items missing were the Teletext module, the horizontal output transistor (Q802) and IC602 (SE115N), the error amplifier. And I knew that the set was virtually brand new – this against Mr Sutherland’s set which everyman and his dog had had a go at and which now had how many faults? I decided to fit a new horizontal output transistor and SE115 IC to the scrapped chassis, then swap the chassis over. When I did this, the sound and raster came on straightaway but no pictures – just wavy, noisy pattern­ing. I thought tuning would fix this. However, five minutes later I concluded that the set was unable to display a picture, perhaps due to the motherboard not having its Teletext module fitted. Chassis comparisons I began comparing the two chassis in closer detail. One was made in Malaysia and the other in Japan, the major difference being the Teletext module. The KV-G21S11 had two extra links fitted, A and B, plus some surface mounted components underneath. Though I tried various combinations of links and swapped the tuners, IF transistors, jungle IC and all coils, I couldn’t get a picture. Reluctantly, I went back to plan A; ie, revert to the original KV-G21S1 chassis and use the borrowed G221S11 as a component source and test bed. First, I swapped IC601, T601 and IC603 to see if I could get any life. I also swapped all the electrolytic capacitors but to no avail. OK, I knew it wasn’t going to be easy. Next, I placed the two sets side-byside and compared the DC resistance to chassis for each pin on IC601. Everything meas­ u red OK until I reached pin 9, where I noticed that the faulty set (G21S1) had less resistance to chassis than the borrowed chassis (G21S11). I then spent some time measuring all the com­ponents around MARCH 1999  21 Serviceman’s Log – continued pin 9 before concluding that C634 (470pF) was leaky. The only problem was C634 was surface mounted, this device being about 1.5mm long by 0.5mm wide and glued on. However, this problem wasn’t insurmountable and I soon had it off and another 470pF capacitor fitted in its place. This turned out to be the culprit and the power supply now fired up, but there was still little life in the set. I measured the main HT rail and got a reading of 150V instead of 115V. Whoops! I quickly switched off and fitted a new SE115N error amplifier 22  Silicon Chip IC (IC602), which stabilised the rail accurately at 115V. I also had 16V on the cathode of D606 and 9V on pin 2 of IC521 but the set was still dead, except for brief periods at start-up during which I could hear the familiar 15,625kHz whistle from the EHT transformer. It was difficult to decide what to try next so I con­centrated on restoring all the desired voltage rails. I replaced several fusible resistors (such as R851) and also IC102 (a 33V IC zener) and eventually re-established each voltage rail but there was still no picture or sound. In addition, the horizontal output stage was closing down after it had been on for about 30 seconds. This turned out to be due to pin 50 of the jungle IC (EHT X-ray) being activated by Q1513 because there was no vertical timebase signal. I replaced IC551 (V-OUT) but it wasn’t until I replaced IC801 (uPC­ 4558G2-EI, PIN-AMP) that the vertical pulses reached the jungle and output ICs and the safety circuit stopped cutting in (IC801 is another surface-mount component). We now had a raster at last but not much else. I was beginning to suspect the main microprocessor IC001 but decided instead to swap IC013 – the memory chip EPROM – if only because it had eight legs and was therefore much easier and quicker to change. Another good move; I now had on-screen displays and move­ment in the raster. Setting up the autosearch produced all the stations in living colour! The sound problem turned out to be the sound IC (IC203, TA8248K). Just for the hell of it, I went back to my Sony friend and told him the full story and he gave me the Teletext module (OPTK200) to try. First, I fitted it into the KV-G21S1 and it worked straightaway. Pressing DISPLAY, 5, VOLUME + and POWER on the remote control puts it into the service mode. I then set up the Text Picture Contrast and Text Mix Mode Picture and Blanking Off Picture according to the Service Manual, then wrote it into memory. I then removed it and fitted it into the KV-G21S11. This restored sound and picture perfectly but funnily enough there was no text. I suspect that in all the messing about, I had made a mistake somewhere. Anyway, enough was enough. I refitted the original chassis and put it aside to soak test while I perused the bill. Mr Sutherland was about to find out what the word “expensive” means. He will probably think that I’m being vindictive but that’s life. Mr Pile’s VCR Mr Pile had just bought a brand new NEC FS-6391 stereo TV set and a VHG-105 VCR from a local electrical discount house and was very dissatisfied with them. This surprised me as it seemed to be a pretty desirable package and I really couldn’t under- stand why he was phoning me, as I was not an NEC dealer. Anyway, he couldn’t get Channel 10 or Channel 28 on the VCR. What’s more, he no longer had any faith in the retailer who had the temerity to deliver and install the combination but didn’t give any lessons on how to use it. In fact, Mr Pile thought that this was disgraceful. I tried to explain to him that, with the profit margins available nowadays, he was actually very lucky to have it in­stalled, let alone delivered. I also asked what was wrong with the instruction book? He disagreed with me, saying that he used to be in the car trade and they would certainly show their cus­tomers how to use the vehicle. I countered by pointing out that everyone takes driving lessons before obtaining a licence; they’re not taught to drive by the car dealers. More to the point, if I was called out, he would be up for my usual service call plus labour costs. He nearly had a coronary with that news but he was persistent and I reluctantly booked him for TV and VCR driving lessons the next afternoon. I arrived at the appointed time and was soon checking out the installation. Apart from little things like skipping unused channel sites and allocating station names, both the TV set and the VCR were installed correctly. The reason he couldn’t get Chan- nels 10 & 28 was because these were two digit numbers and the “-” button on the remote keypad had to be selected first. It was all in the manual, if only he’d taken the trouble to look. The VCR was connected via AV leads to get the best audio quality and is selected via the TV/Video button. I then set the VCR time via the menu (i) on-screen display system (OSD). Mr Pile had enormous difficulty in following this as he wasn’t used to concepts such as menu, enter (OK), memorise, edit, scroll and other computer type jargon. It became worse when I explained how to do timer recordings and record one channel while watching another. He had great difficult in keying in the numbers and often mis-keyed without checking for confirmation on the screen. I did my best to per­suade him to use G-code, which on this VCR did not need setting up, much to my relief. After an hour and a half and after watching him practise it five times, I finally managed to extricate myself, having charged for only an hour. Another call The next morning, there was a message on my answering ma­chine, logged at 7.15am, complaining that the system was still not working. I did my best to fix the problem over the phone but in the end I had to go back. This time he had made a real mess of it and the tuning of the VCR was all over the place. When I reconstructed Mailbag: continued from page 31 in the subject of technolo­gy. We collect old fax machines, disc drives, CD players and many old photocopiers. This last item results in many excellent motors, gears, clutches, chain, steel rods and bearings, to name just a few. With all this junk we have made many small model sanders, robots, cranes, miniature drill presses, small lathes, trucks and so on. One small problem does arise. A few motors are of the stepper type. Your excellent project on the “Universal Stepper Motor Controller” has been used on several occasions. I am work­ing on a modification to this circuit, to make the board much smaller, as on most projects we do not need the stepper function; just on at full speed and occasionally reverse. We have close to 50 of these, some with excellent worm drives and gearboxes – very useful. L. Beswick, Newnham, Tas. Doesn’t like digital phones I read with interest your article on page 44 of the January 1999 issue regarding Dick Smith Electronics selling a digital mobile phone for -$1. Your article states that there are over 1.8 million analog users yet to convert to digital. Perhaps I know why. I will now transfer to a digital phone. Many of us anaee a mobe aaa eee useee preaaaee th method mobile communieeeeaaa beep beep beep. Oh, I’m sorry, you didn’t under- what had happened, I discovered he had tried to get into the timer pro­ gramming menu but had accidentally placed the cursor on the wrong item and had selected the automatic tuning instead. This tunes all the stations automatically from program 01 until it stops. It took nearly half an hour to put it back the way it was and give him one last lesson. Of course, he had no intention of paying for any of this. I left him with instructions that he was now on his own; I would only help him over the phone and I wouldn’t call out again. I left with my fingers crossed. That probably sounds callous but I can’t afford too many free calls. The truth is, I have a great deal of sympathy for this customer and a lot of other customers who have similar problems. The problem is that many people really don’t understand current technology and are frightened of it. There certainly is a market for “nofrills” basic TV sets and VCRs using remote con­trols with large buttons, idiot-proof on-screen displays and LEDs to show that they are transmitting. In addition, the instruction booklets should be easy to read and understand. The manufacturers could help in this regard by not using jargon or new buzz words or incomprehensible acro­nyms. I know of one case where someone sent for an instruction book to explain his instruction manual – SC and received one! stand the last paragraph. Well, with the way these new-fangled phones “digitise” I’m not surprised. Many of us mobile phone users prefer analog as the method of communication because we can still hold a conversation in suspect signal areas and our phones work where digital ones don’t. I know of many analog users who will hang on to their phones until Telstra finally “flick the switch” because they know the digital system just doesn’t live up to the advertising hype. Dealers can offer any figure they like to convert. I for one will keep my Motorola “Brick” on line as long as the little green LED in the top left hand corner of the display keeps flashing. B. Sheargold, Collaroy, NSW. MARCH 1999  23