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The risk of passing the buck The more complex our technology becomes, and the more specialised the services needed to keep it working, the more risk there is that. one specialist will pass the buck to another while the customer gets little or no service. It's something we need to watch. Something like that could have happened with the story I'm about to relate. The fact that it didn't was due to a number of factors; the honesty of a colleague, the patience and understanding of the customer, and what I like to think of as a policy of attention to detail on my part. And if that last remark sounds at all self-righteous it is not meant to be. It is no more than good business practice; the kind one needs to stay in business. Anyway, enough of the philosophy, let's get on with the story._ It started about 18 months ago and mvolved one of my long standing customers who owns a Thorn 63TI colour TV set. This set uses an AW A "Q" series chassis and is about 6 years old. Also important is the fact that he lives on an escarpment overlooking the sea, in one of our southern seaside suburbs. And in certain conditions, he cops a lot of salt spray; something which plays havoc with all metal fittings from door hinges to TV antennas. The site, in the TV sense, is a bit of a mixed bag. To the north, in the direction of the local VHF transmitters, it is quite severely shielded. In fact, he just about gets by. On the other hand, he has a clear path down the coast to the south. UHF channels It was for these reasons that he pondered the possibility of being able to receive the UHF transmit- 74 SILICON t.HTP ters then being set up to the south of Wollongong. One attraction here was the fact that major sporting events are often blacked out in Sydney but are available from outof-town transmitters. In fact, a number of clubs were then installing eleborate UHF antennas so that they could receive these sporting events from Wollongong. I was also aware that other viewers in this general area, in favourable locations, were receiving quite acceptable signals. So when he put this idea to me I agreed that it might just work. But I do very TETIA TV TIP Philips KT3A·1 chassis Symptom: Set hiccupping. Both line output transistor and tripler ~ere changed, without any success. E-W diodes D562 and D567 were removed for checking, and the fault was found as they were being replaced. Cure: Dry joint at the earthy end of C567, where it joins with C562 and the two E-W diodes. It's hard to see why this fault had such a dramatic effect but obviously the circuit relies on the full capacity of C562 being present. TETIA TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania 7015. little antenna installation work these days; just keeping the workshop running is a full time job. Instead, I normally refer such work to one or other of my colleagues who specialise in antenna installation: field strength surveying, selection of antennas and the erection of suitable masts. So my colleague duly visited the site and made the survey. The results were a bit "iffy", and my colleague advised against making an immediate decision. Not all the transmitters were yet running at their full authorised strength and he suggested waiting until the whole system was up and running. The customer was happy enough to accept this advice but suggested that, while he was there, my colleague give the existing VHF antenna and coax a general overhaul. This was duly done and involved little more than a general clean-up and the securing of some loose coax. After that, all went well for a few weeks until the customer complained to my colleague that performance on the VHF channels seemed to have deteriorated somewhat. My colleague went back, checked the antenna mechanically, then made another field strength measurement. This produced figures similar to those taken before; in other words it was not an antenna problem. So was it the set? He didn't feel competent to make a firm decision on this but a rough check suggested that the set might be a bit down. It produced an acceptable picture when fed via the owner's video recorder (due to the extra gain of the recorder) but was quite poor when fed directly from the antenna. So the ball landed back in my court. I try to avoid house calls as far as possible these days but this was clearly a case where the pro- blem had to be assessed on the spot. So armed with my own field strength meter, I made the call. And my findings seemed to tally with my colleague's; signals from the antenna were about what I would expect but I had to admit that the overall performance seemed more marginal than previously. I offered to take the set back to the shop and give it a complete check but the owner elected to let things stand for the present; he could get by and had some programs he wanted to be sure of seeing. So we left it at that for the moment. Snow & confetti A few more weeks went by and then there was another call for help. It was no marginal situation this time; for all practical purposes all signals had been lost. So I made another call. And he was right; there were just some faint images behind a curtain of snow and confetti. Fortunately, I had taken the field strength meter with me again, otherwise I may have gone off on a false trail. Because, although it looked like the set was at fault, it was really the antenna. So what had my colleague done wrong? Nothing really. I noticed that the customer had a team of painters on hand and, in answer to my query, he realised that the signals had been lost about the time they started work. I went outside and took a closer look at the coax. This comes in under the eaves from the mast, runs down the wall where it is held by a series of nail-in clamps, and then runs under the house and up through the wall cavity to an outlet in the lounge room. And the painters, in their enthusiasm, had pulled the cable away from the wall - by the cable itself apparently - in order to make a smooth paint job. They'd also made some attempt to put it back in place but it was a clumsy effort and all too obvious. The result was equally obvious to the ohmmeter; the cable was open circuit. So my colleague was called back again and a new run of coax fitted. That put everything back to more or less normal but it had all been a bit of a circus. Privately, I hoped that that was the end of it. But it wasn't. Several weeks went by and then came another call for help; the system had dropped its bundle again. The owner had been in two minds whether to call me or . my antenna colleague but finally chose me because he felt that the antenna had been so thoroughly worked over that it had to be the set this time. And he was right. I took my field strength meter along and quickly confirmed that the antenna was doing its job. So it was the set and my first reaction was that it was probably a tuner fault. In any case, it was not a problem I was prepared to tackle in the customer's lounge room so I loaded the set into the van and took it back to the shop. On the bench I made a few routine checks and I was contemplating what to check next when I suddenly had an impulse to check the AGC trimpot setting. It wouldn't be the first time that I have found that, for one reason or another, this setting is less than optimum. And in any case, the set's behaviour when this is adjusted can sometimes produce a few clues. Anyway, I slipped a screwdriver into the slot and exerted gentle pressure in an effort to turn it. And that was all it took. The set suddenly burst into life and produced a bright snow-free picture with all the indications of maximum sensitivity. Further tests confirmed this the only fault had been a dead spot on the AGC trimpot. I was a little surprised at this because it appears to be a quality component, with the track on a ceramic base, and very well made all round. It was only much later that the full significance of its failure became apparent. For the moment it was a simple replacement job, although I didn't have the exact type available. The closest I had was of similar quality and fitted physically. So the set was back home in a few hours and it hasn't missed a beat since. Shoving ducks That, technically speaking, is really the end of the story, although there is more to come on the same theme. But the point I hinted at SEPTEMBER 1990 75 SERVICEMAN'S LOG -CTD earlier is worth some attention. This is the risk of confusion and buck-passing when, as in this case, a service problem has to be split two ways. It is all too easy for an antenna technician to duck-shove a difficult situation by blaming the receiver, or for the serviceman to do the same by blaming the antenna. That simply leaves the unfortunate customer as the meat in the sandwich. And it has happened, as I'm sure some of my readers could testify. Fortunately, in this case, we know each other and respect each other's work. Which is how it should be. But to get back to technicalities, as I said that was the end of the story as far as that set was concerned and I soon forgot about it. Then, a few weeks ago, another set fitted with a "Q" chassis, an AW A C5319, landed on the bench. This was a later model but uses essentially the same chassis. And it also came from a site on the edge of a bay where it was subject to salt spray contamination, although the significance of this as.caped me initially. The complaint was partial frame collapse, the picture being only about two thirds normal height. I slipped a screwdriver into the height pot to make an exploratory adjustment - which can often reveal a lot about this fault - but got no further than exerting a minimum of rotary pressure. Then the picture collapsed completely and it took a deal of fiddling to get it back again - and then only with a setting that gave gross overscanning. Naturally, it was the trimpot the same type of pot. which had failed in the set in my first story. But that was not all. Having replaced the pot. and set up the height correctly, I decided a smidgin of linearity adjustment might be appropriate. But this pot. (another of the same type) turned out to be so jumpy as to make the job impossible. So that pot. was also changed. That was the end of that story. But a couple of weeks later another "Q" chassis (an AWA C5328 just out of warranty) appeared from a customer who lives almost opposite the owner of the set I have just described. His problem was poor sensitivity; the picture quality had become progressively worse over the last couple of months, until i~ was now virtually unwatchable. He had called in my antenna colleague, who had made a field strength reading, pronounced it normal, and then confirmed this with a portable set which produced a normal picture. So it was over to yours truly. The proverbial dog A quick check confirmed that the set was as sick as the proverbial brown dog but I had more than a gut feeling that I knew what was wrong. Sure enough, as soon as I touched the AGC pot. the set sprang into life. I replaced the trimpot, adjusted its setting, then checked the height and linearity trimpots on spec. But they were OK, so that was the end of episode number three. Episode number four involved an AWA C5324 "Q" chassis, and happened only a week or so ago. It came from the same general locality, was also not long out of warranty, and was another case of partial frame collapse. I replaced the height trimpot, then checked the linearity pot. It was also jumpy, so I replaced that as well. Having set up the height and linearity, I realised that there was a colour balance or grey scale problem. This turned out to be due to incorrect setting of the G2 pot. in the green gun. This, in turn, was due to yet another of these pots. which had gone erratic. So that too was changed. All the others seemed to be OK. So there we are; four sets and seven trimpots, all from a salt laden area. Which is significant because I cannot recall ever having had any other trouble with these pots in other areas - and a goodly number of "Q" chassis have passed through my hands over the years. It simply means that these trimpots, reliable as they are in most environments do not like to be beside the seaside'. She'll be right mate --..11 ~-"'.::,i;...;:_ 76 SILICON CHIP And now for a change of scene, here is an incident related to me by a colleague from the Illawarra district, south of Sydney, which is slowly being changed over to the UHF TV system. And although he relates one particular incident, he stresses that it is becoming an increasingly common one. This is how he tells it. This story concerns one of my customers from way back who purchased an AW A video recorder (model AV52), although I hasten to emphasise that this is no reflection on AW A. It could just as easily have been any brand you like to nominate. It is also important to add that this customer lives some distance out of town in a poor UHF signal area and this compounded the problem somewhat. On the other hand, he did have a good antenna set-up, covering the local VHF channels, the Sydney commercial VHF channels, plus a recently installed UHF array. It all started about a month before I came on the scene, when this chap had bought the recorder, as a result of a "special offer" by an out-of-town outlet. It was one of those transactions where the recorder was simply handed to him in its sealed carton, with the salesman's assurance that he would find all the necessary instructions in the manual inside. In TV TEST EQUIPMENT (AUSTRALIAN MADE) 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-VOLT AGE PROBE Built-in meter reads positive or negative 0-50kV. Can also be switched to check negative voltages. For checking EHT and Focus voltages as well as TVs and Microwaves. Hi-tension voltages. $98.00 + $5.00 p&p LOW-VOLT AGE PROBE Ideal for checking microwave ovens and TVs. The ~ ranges are from Oto 5kV and from O to 1 OkV. Double insulated for safety. $79.00 + $5.00 p&p m happening. From his attempts to explain it I gained the distinct impression that, with the VCR in circuit, he could not even get normal reception on the TV set. And as for signals via the VCR's tuner, the best he'd managed was a couple of snowy pictures but he wasn't even sure which channels they were from. The only thing he was sure of was that the so-and-so VCR was no so-and-so good and he reckoned that it ought to be fixed under warranty. Which was fair enough if the thing was crook. So I said, "Bring it in and let's have a look at it". I was quite prepared to find that he couldn't get signals through the VCR into the TV set. It is not the first time this has happened. A faulty splitter amplifier would be the most likely cause. But that was only a figment of his confusion. On the bench the recorder performed perfectly as a link between the antenna and a bench set. On the other hand, trying to get signals through the recorder's tuner into the TV set which I guess was what he had other words, "she'll be right mate". Well, this bloke took it all home and poured over the manual. But we all know about manuals, don't we? They make beaut light reading after you've worked out - or been shown - how to use the device. He did manage to work out the connections between the antenna, the recorder and the TV set. Then he tackled the job of setting up the VCR tuner etc. And this is where it all went horribly wrong. It was quite an undertaking anyway, because he was aiming for five UHF channels, two local VHF channels (4 & 5A), plus the three Sydney VHF commercial channels (7, 9 & 10). That can be quite an involved job even when you know what you're doing; it can be positively frightening the first time around. The end result was - not to put too fine a point on it - what one of our politicians would call "a monumental screw-up". And so he was on the phone to me. And such was the order of his confusion that he was unable to give me a clear picture of what was ANTRIM TOROIDAL TRANSFORMERS QUALITY TOROIDAL POWER TRANSFORMERS, MANUFACTURED IN U.K. NOW AVAILABLE EX-STOCK AT REALISTIC PRICES. General Construction Ou1£A tNSUl,.IION OUllll WINDIIIIG - DEGAUSSING WAND Strong magnetic field, larger than usual coil with multicore centre. Double insulated for safety with momentary switch operation. 240VA/C 2.2 amps. As important as having a soldering iron! $75.00 + $10.00 p&p TUNER REPAIRS We repair most tuners on an exchange basis. From only $17 .00 + p&p The Largest ex-stock source of toroidal power transformers in Australia. Models available to suit most project kits. Specials made to order. Enquiries from resellers and manufacturers welcomed. Quantity and tax exclusive prices available on request. Call for data sheets. Cheque, Money Order, Bankcard or MasterCard -:T.V.TuNERs) 216 Canterbury Road, Revesby, NSW 2212 Phone (02) 77 4 1154 HARBUCH ELECTRONICS PTY LTD 90 George St., HORNSBY NSW 2077 Phone (02)476-5854 SEPTEMBER 1990 77 SE:\J~N "'t~IM'POTS F\L.L FROM ~ .SAl--r LAOE-N been trying to do, to confirm that the tuner settings were correct revealed a hopeless mess, even from my antenna which delivers quite adequate signals. He had managed to get close to a couple of channels; close enough to lock the picture but nowhere near close enough to make the best use of the much weaker signals at his place. But the real gaff was that he thought he had tuned in the two local VHF channels, whereas he had actually tuned in the UHF channels which were relaying these programs. Verily and forsooth, confusion had reigned supreme. I spent about 20 minutes setting up all the channels he wanted, which gives some idea of what's involvE;Jd, considering that I didn't have to work it out from the manual. The result was pretty good, though I doubted whether he would do as well at his place, and I warned him about this. Then, with this thought in mind, I made some sensitivity checks on both the VHF and UHF channels. I've been caught before this way on nBw equipment. There's seldom much wrong with the VHF side but UHF is a cl.ifferent matter. The sen- P.:RE;.A sitivity of the tuner can vary greatly, even from set to set of the same model. So a set which appears to be OK in a good location may be quite useless in a lesser location, even though another such set will perform well. So the only sure answer is to measure the sensitivity. In this case, the readings were good so I felt that the client would get about the best results possible from his set-up and location. It must have been good enough, because he was quite happy with everything the next time I saw him. Philosophical reflections It's not always like that. Sometimes UHF performance on a new TV set or recorder is way down, in which case it should go back to the firm concerned. On the other hand, it is sometimes only marginally down and that makes it hard. In such cases, I usually find it difficult to get much satisfaction. There will be excuses, arguments about equipment accuracy, and much buck passing. The whole exercise can be very time consuming and seldom very satisfactory for the customer. So I am more or less forced to ig- .1.m:.,.;. ri:.~:i:.11~ RCS Radio Pty Ltd is the only company which manufactures and sells every PCB [, front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. 78 SILICON CHIP nore it unless there is a very strong case. Yes, I know it's not fair but that is about the state of the art, UHF wise, at the present time. As for this exercise, the only slightly sour note was the need to charge for my service. In fairness to the company concerned, I could not claim for repairs under warranty. There was nothing wrong with the recorder; just the client's inability to set it up. I did keep the charge down to a bare minimum and he didn't complain. But my original dig at the salesman, the read-the-manual she'll-be-right-mate type, still stands. What happened wasn't the client's fault. It is ridiculous to expect the average bloke in the street, skilled handyman though he may be, to tackle a job like this, even with a good manual - and I've yet to see one of these. More to the point, this was not an isolated incident. More and more I am being called on to set up VCRs and TV sets which people have bought in similar circumstances. Most of them have no idea that any setting up is involved. They fondly believe that they can take it home, connect power and an antenna, and it will bring in all the stations. When it doesn't, they imagine, as did this client, that there is something wrong with it. And not all of them are so philosophical about paying for the job. So what's the answer? Should such specialised equipment be sold without adequate installation backup? Granted, it probably means an attractive first cost but much of this is lost if the buyer has to call in a serviceman to get the thing working. Nor is it fair to expect the manufacturer to carry this cost via warranty. After all, the retailer's mark-up is supposed to cover this service. So I suppose it's a case of "buyer beware" but that doesn't seem quite fair either. Well, that's my colleague's story and it offers a sobering insight into TV problems outside our city areas. My colleague also had quite few remarks about the problems being encountered in establishing the UHF service. I might encourage him to expand on this in a later issue. ~