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SERVICEMAN'S LOG All the IDakings of a Chinese puzzle Servicing often involves more than electronic expertise, experience and a set of service manuals. Knowing what to expect in particular sets often means knowing something of the manufacturer's history and even, as in this case, where the set was made. This was brought home quite forcibly by a recent experience with two TV sets, supposedly identical but actually as different as chalk from cheese. Both were 36cm GC-149 colour sets, made under the General label. Now the General label has had a somewhat chequered history. Originally a modest-size Japanese company in its own right, its sets were very popular and they appeared on the Australian market with the introduction of colour TV. More recently - about five years ago - the company was taken over by Fujitsu and many models are now sold under the Fujitsu General label. On the other hand, and rather strangely, some still carry the simple General label. (The company is represented in Australia by General Corporation Australia Pty Ltd , 10-16 South St, Rydalmere, NSW 2116). Routine but interesting The first set did not present any complex problems and was fairly routine in fact. But it was interesting in other ways. It was a faily new set, only some six months old and still under warranty, and was owned by one of my long-standing customers. More importantly, in this context, he is one of those loyal customers who would never consider taking a set to anyone else. The complaint was straightforward enough: sound and raster, but no picture. I pulled the back off the cabinet and this gave good access to several 72 SILICON CHIP useful check points. These included the R,G,B stages and I checked the voltages on the relevant transistor collectors. These all came up very close to the 123V shown on the circuit. I checked these same points with the CRO and wasn't particularly surprised to find no signal. Nor was there any signal on the bases of these stages. Again, no great surprise. From here I jumped back to the luminance circuit and, specifically, to the video drive stage, Q201 (2SA733AP), which is fed from pin 48 o( the jungle IC, IC201 (UPC1420CA) - see Fig.1. An output is taken from the emitter of this stage but there was no luminance signal at TETIA TV TIP Rank C-1851 Symptom: weak sync. Flagwav• ing at top of picture on reception of TV channels, total breakup of picture when viewing video recordings. Cure: C556 (10µF 16V electro) dried out. This capacitor passes pulses from the AFC pulse amp (TR505) to the flywheel discriminator ahead of the line oscillator. TET/A TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler. 16 Adina St. Geifston Bay, Tasmania 7015. this point. Nor was there any at the base, which couples to pin 48. Back tracking from here took me to transistor Q3, the first video amplifier. There was luminance signal at the base of this stage, and also at the emitter, from whence the signal goes to pin 42 of the IC. So yVe had signal into the IC but no signal out. Before jumping to conclusions, I checked the voltages on the IC pins. These voltages did not tally exactly with those on the circuit they seldom do - but there were no gross abnormalities, and I felt my original suspicion was justified; the IC was crook. I didn't have a replacement and it is a type I don't normally stock. The failure rate is low and it would be stock lying idle. Nor was I keen on buying a replacement since, under warranty, I would not be reimbursed financially but only with a replacement device - which I might not use for years. So the plan was to remove the suspect unit and return it to the local company for direct replacement. A real mess It was only then that I removed the main board and turned it over to attack the IC connections. And what a sight met my gaze. If I hadn't known . the set's history and the honesty of the owner, I would have assumed that some striped apron merchant had been at it with his traditional tools of trade. Not to put too fine a point on it, it was a right proper mess. And since I did know its history, it was obvious that this was the way it had come from the factory. Now it is not unusual to find, in any new set, that there has been some additional work done in the factory. As sets come off the production line and are given a preliminary test, there will inevitably be a small proportion that don't work. · These will be diverted to a production service bay, the faulty compo- 3 /l4BLII C15 NA TERM! NAL o.o, ·o Cl 51 1------1 CHROMA PROCESSOR VIDEO AMP SYNC AMP.VERT OSC.HOR.OSC IC201 UPC1420CA R.l06 s.&< C31 \ \!S(]P C3\2 \!S(]P C3\3 1110P n~ ~~,...~-it-.-_-_-_-r--.-v-------i~---0-~ . Fig.I: relevant portion of the General GC-149 circuit. The jungle chip is at the bottom, the video driver stage (Q201) at left above it, and the 1st video amplifier transistor (Q3) at top centre. The problem turned out to be simple enough, although the PC board on which the parts were mounted was a real mess. nent or connection tracked down and replaced or repaired, and the set returned to the testing line. And one can usually spot such work; a hand soldered connection will leave a ring of rosin flux - something which doesn't happen with the flow soldering process. Nor is there any objection to this procedure. After all, it would be stupid to discard a whole board, simply because one minor component was faulty. But there was nothing minor about what had happened to this board. For starters, cuts and scratches had been made in the board between most of the pins of the IC in question, and pretty roughly at that. The green varnish which normally covers the board had been scraped and cut, and some of the cuts were quite deep. But it wasn't only around the IC. There were quite a number of cuts at odd random spots on the rest of the board. The meaning of life What did it all mean? Was I wrong in my diagnosis of a faulty IC? Was there some more subtle fault, possibly intermittent, which had eluded the factory tests and was now in my court? JANUARY 1991 73 arrived and was fitted. And that was it, the set worked first time and turned in a first class performance. Beauty really is only skin deep! So the set was duly returned to the customer, who was delighted with the performance. But he was quite shocked to learn that it had been made in China, rather than Japan, where he imagined it had been made. Truth to tell, I doubt if he would have bought it had he known. On the other hand, there was no point in worrying him unnecessarily - the set could go for years and never miss a beat. So I kept my findings and impressions to myself, simply answering his inevitable question with the truth; it was a faulty IC. SERVICEMAN'S LOG - CTD Perish the thought! In any case, the IC would have to come out and be replaced. If my worst fears were realised, someone else, like the local General Corporation, could take on the job. But the whole situation alerted me to something I had overlooked up until this point. The set had not been made in Japan - they would never allow a set like this to reach the market. Nor had it been made in Korea, where the quality control, while not quite as good as that in Japan, would never pass anything like this. No, the fine print on the spec. plate indicated that this set had been made in The People's Republic of China. This was the first time I had encountered anything from this region and, superficially at least, it appeared to be exactly the same as the versions made in Japan - even down to the components used. A grotty effort There was only one exception; the printed circuit board. Forced to look at it closely I realised that it was a pretty grotty effort, with very rough edges and dags on the copper tracks. While the other major components had obviously been imported, I tip that the board had been made in China. And this, I suspect, was the reason for all the cuts and scratches; the rough copper pattern had resulted in bridges between tracks, preventing the set from working in the first place. There may have been only one or two such bridges, but the technician had adopted a blanket approach, cutting and scratching between all suspect tracks until the set came good. This, in turn, suggested a fairly low level of service expertise, low labour cost, and a situation where time was of little consequence. And in support of that last point I would judge that several hours had been spent working on that board; a lot longer than would be tolerated in most factories. Nor was this service confined to cuts between tracks; closer investigation revealed that several copper tracks had been cut and subsequently bridged. Obviously another blind approach to solving the problem. And in a couple of cases, the tracks haq. been cut and left cut; apparently part of some modification process which must have been legitimate, because the set had ·worked (and eventually worked again). Anyway, there was little I could do about that; time did not permit a detailed analysis of situation. I simply pulled the IC out and sent it back to the company for replacement. Then I went over the board and did my best to clean it up. There wasn't a great deal I could do but it did look a little better when I'd finished. Granted, it wouldn't make the set perform any better, but it did give me some satisfaction. In due course, the replacement IC Dropped General And that brings me to the second version of this set. In fact, it came into the workshop while I was still working on the first one. The owner is another regular customer and he was somewhat agitated. He was leaving on an extended caravan holiday the following day and was loading the set into the van when he dropped it. Now it didn't go! Could I have a look at it and perhaps do an emergency repair? Surprisingly, there wasn't a mark on the cabinet even though, by all accounts, it had taken a pretty hard knock. But one glance inside told the whole story and points up what I consider is a serious weakness in many sets on the market today. The main board sits in the bottom of the cabinet, supported by its right and left hand edges, which slide into 0 ••• ~-r TM~ TV , 1'HE 'PEOPLES 'RePUSt.-1C OF ClilN~ •• 74 SILICON CHIP slots moulded in the cabinet. And that's all the support there is. When it receives a jolt, even a relatively mild one, the weight of the horizontal output transformer is just too much, and the board cracks. That was exactly what had happened in this case, which didn't really surprise me. In fact, I already had an AWA Mitsubishi in the workshop which had suffered the same fate. Again, there was no damage to the cabinet and, as far as I could determine, the drop had been quite moderate. Nevertheless, the board had cracked under the horizontal transformer, severing about 10 tracks in the process. But that's another story. The damage to the General was more severe. It had cracked roughly diagonally across the rear right hand corner, under the transformer. Fortunately, it had not cracked right across, so there was still some mechanical support. I went over it with a glass and, at a rough count, there were 37 broken tracks. And those were only the ones I could be sure of. I shook my head; even assuming that I could find time to do the job in the few hours available, there was no way that I could guarantee it, with the set being jolted around in a van. To have any chance of a permanent cure I would need to run it on the bench for a substantial period, give it a good shaking from time to time and, ideally, subject it to a range of temperatures. And even then, we'd both have to accept that it might bounce after several months. But a quick fix for use in a van? No way. When I made these points to the owner, he accepted the situation philosophically. "I'll go out and buy another portable. You hang on to that one and see what you can do with it while I'm away. See ya in a few months". Easier than I thought And so the set was pushed into a corner until such time as things were slack; an ideal way to tackle a job like this. In fact, the repairs to the board took less time than I had anticipated and went without any problems. But I couldn't help noticing the difference between this board and the previous one. Both sets were made in China but this one was as neat and well made as any I have seen. Is Your Product Or Service Getting The Exposure It Deserves? 25,000 consumers will read this page. They need to see your advertisement if you want them to buy your product. Contact Paul (018) 28 5532 or Ian (03) 696 5411 to reserve this space. So I pass. More to the point, the set functioned at first switch-on, which was more than I had hoped for. Unfortunately, after my initial elation, I realised that all was not perfect. It was exhibiting more than normal purity error in the top left corner (bluish) and about halfway down the right hand side (magenta). Apparently, the fall had moved or distorted the shadow mask slightly, and there is little that one can do about that, at least directly. The real solution would be a new tube but the cost would be hard to justify. The best I could do was give it a purity adjustment and hope that I might score some improvement. So I slackened off the yoke retaining screw, and juggled the assembly for the best result. I didn't score a great deal but any improvement was worthwhile. Then I re-converged it and this came up very well. So the final result was usable even if something less than perfect. To tell the truth, I imagine most viewers would probably be unaware of the fault unless their attention was drawn to it. And there this job rests, still in the workshop, waiting for the owner to TV TEST EQUIPMENT THAT WILL EARN YOU MORE MONEY (AUSTRALIAN MADE) 12 Months Warranty SHORTED TURNS TESTER Built-in Meter to check EHT transformers including split diode type, yokes and drive transformers . $78.00 + $3.00 p&p HI-VOLTAGE PROBE Built-in meter reads positive or negative 0- S0kV. For checking EHT and focus as well as any other Hi-tension voltages. $98.00 + $5.00 p&p LOW VOLTAGE PROBE Ideal for checking microwave ovens and TVs. The ranges are from 0 to SkV Negative and from 0 to 10kV Positive. Double insulated for safety. $84.00 + $5.00 p&p &p . $75. • ,.... DEGAUSSING WAND 7,700 apere turns. Strong magnetic field, larger than usual coil with multicore centre. Double insulated for safety with momentary on/off switch. 240V NG 2.2 amps. This one is just about as impot1ant as having a soldering iron in your toolbox! ... ..,. <REMOTE CONTROL TESTER . (INFARED OR ULTRASONIC) $85.00 + $4.00 p&p TUNER REPAIRS TV . Designed to test any lnfared or Ultrasonic control units. With the extension lead you can also test infared units which cannot be placed in front of the testing unit. Requires a 9V battery . Output is via the LED diode and piezo speaker. trom only . we also repair most tuners on an exchange basis. "• • s11.oo + p&p Cheque Money Order Bankca;d or Masterca~d 11JNER51\216 Canterbury Road, Revesby, ~ NSW, 2212, Australia Telephone (02) 774 1154 JANUARY 1991 75 ~ ~~~<at> o• ~ t·~~/J ' ; l f ~?~ ~ ~ - ( ~ ~~~~~:::~ ~~ 14 I .) ' ' iE r al l llh I' return from holidays. I hope he won't be too disappointed. But the moral is obvious; TV sets don't like being dropped. The ghostly antenna And now, for a change of scene, here's a funny one from my southern correspondent, J. L. of Tasmania. And when I say "funny" , it was more "funny peculiar" than "funny ha ha". Here's how he tells it. This is a tale about a ghostly car radio installation. It comes from a colleague who runs a small business specialising in mobile communications. To appreciate the story, it is 76 SILICON CHIP first necessary to understand how an automatic radio antenna works. These systems usually have two leads (plus an earth) attached to the antenna actuating motor. One is a permanent connection to the 12V supply while the other is a control line and is usually connected to a switched 12V output from the radio. This operates a DPDT relay to control the direction of current flow through the motor. When the control line is low (ie, at 0V), the relay connects the antenna motor in the "down" configuration and the antenna retracts until, in the fully retracted position, a limit switch is activated. Conversely, when the control line is energised, the relay switches the motor to the "up" configuration and the antenna extends until, at full height, another limit switch is activated (see SILICON CHIP, March 1990, page 30, for additional details), In the ideal case, the control line is connected to the switched 12V output on the radio. This is energised when the radio is switched on, thus causing the motor to run forward and raise the antenna. If the radio has no such outlet, an alternative approach is to connect the control line to the accessory position on the ignition switch. In this case, the antenna will be raised whenever the ignition switch is in the running or accessory position, and will be retracted when the ignition is turned off. Now to the story. It seems that a new radio had just been fitted to a vehicle, along with an automatic antenna, when the customer arrived to take delivery. The last connections to the antenna control circuit were still to be made and the installer was working against time. And, since this radio did not have an automatic antenna power outlet, the control line had to be connected to the accessories terminal of the ignition switch. The installer turned on the ignition and searched for an active 12V line. He found one and connected the control line to it. The antenna worked perfectly, and so did the radio - for about three days. Then the owner found that whenever he turned sharply left the antenna retracted, then went up again as he straightened up. The same thing happened when he accelerated - the antenna would retract and then shoot up again as he eased off the pedal. It reached the point where, in stop-start traffic, the antenna was continually winding itself up and down, which made reception virtually impossible. This pattern continued for a couple of days then cleared up, only to show up again later in the week. The owner wasn't too happy about it and brought the car back to have the antenna system checked. Just fill 'er up This time it was examined by a technician, rather than the installer, ·and he found a most bizarre reason for the problem. The 12V control line had not been connected to the accesories side of the ignition switch, as intended, but to the petrol gauge line. At the time the installation was done this line measured 12V, but this value was fated to vary as the fuel level dropped. With a full tank the system worked normally but, as the level dropped, the fuel sloshing about put lower and varying - voltages on the antenna control line, which eventually dropped below the hold-in level of the relay. Hence the mysterious effect. In fact, if the tank had been taken down to nearly empty the antenna would not have worked at all. The symptoms cleared each time the tank was filled but, in between, the owner thought his car was haunted! Which just goes to show that it doesn't pay to rush any job that even remotely involves electrical connections. Serviceman's boo-boos Thank you J. L. That's a new one on me. Very early in my career I earned HAUN"i'E.D( NO StR; '(OUR CAR IS ~ST E.X_C-1 i""E:-D :I my bread and dripping fitting car radios to the then popular vehicles like the Austin A40 and the first Holden. And we had our fair share of boo-boos. I once witnessed an incorrect connection behind the dash destroy a whole wiring loom on a brand new car. What the boss said to the hapless perpetrator doesn't bear repeating. At a personal level, the worst experience was more painful than anything. Groping behind the dash for a connection I managed to bridge an active terminal to chassis via the metal strap on my wristwatch. Almost before the pain registered it had melted two links out of the strap, and left their imprint burned into my wrist. The scar has now faded but was visible for several years. But patching into the petrol gauge no, we never did anything like that; that takes the prize. Correspondence And finally, I feel bound to reply to a reader, R.W.H. of TasmanJa, who has written to the editor, questioning some points raised in my October notes. His letter was reproduced on the Mailbag page of the November issue, together with a brief editorial comment. I refer readers to this for the full text. As far as the transformer is concerned, there is little that I can add to the editorial comment; my sentiments entirely. However, the transformer in question is sitting on my desk as I w:&ite and, if R.W.H. would like to conduct his own research, he can have it for the price of postage and packing! And the supposed excessive charges? Nowhere in my notes did I state that the customer was charged for the replaced driver transistor, Q501. Experimental replacement of minor components like this are a normal part of everyday sevicing. If it cures the fault, well and good; if it doesn't, one writes it off as a few cents - or even dollars, sometimes well spent. And it is a lot cheaper than wasting hours using alternative approaches. In fact, all the customer was charged for was the transformer and the output transistor, Q551. And, yes, the customer was told to " ... bring the set in right away"; and he agreed to do that. I rest my case. SC PHONE LINE AND MAINS FILTER/SURGE PROTECTOR Protection tor swering machines rdless phones csimiles The Arista model CPEP-1 ensures that lightning, power surges and spikes do not reach your costly communication equipment as it constantly monitors the PHONE line and the MAINS power line. 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With each purchase of a packet of plastic cable ties at the SPECIAL PRICE below you will receive a 12 month subscription to 'Silicon Chip', which has been prepaid by Sound Australia.Why do we make such an offer? We want you to try us at least once, even if it costs us money to do so. If you already have a subscription we will be happy to supply it to a friend, you nominate, with your compliments. 500 95mm x 3mm Cable Ties $30.00 Bonus Subscription ~ Your Price $30.00 500 190 x 5mm Cable Ties $65.00 Bonus Subscription ~ Your Price $30.00 PHONE TODAY FOR THIS LIMITED OFFER SOUND AUSTRALIA 28 Walker St. Dandenong, VIC, 3175 Telephone: (03) 7911622 JANUARY 1991 77