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SERVICEMAN'S LOG Whistles aren't always carefree As a kid, I had quite a repertoire of whistles. I could whistle on a gum leaf, I could whistle through my teeth, and I could whistle through my hands. Unfortunately, not all whistles bring such simple pleasure. critical, due to standing waves in a room and the disposition of furniture and curtains. In addition, the actual level itself can vary due to temperature changes and other factors. All of which can easily add up to situation where a customer can hear it and a salesman, or serviceman, cannot. It's not so bad if the salesman or serviceman knows that this can happen. But if he doesn't, it can lead to serious misunderstandings and to a totally dissatisfied customer. More about that later. In this case, the set belonged to a young couple, was about one year old, and was still under warranty. The wife rang me and complained about an "annoying noise" coming from the set but without much indication as to the nature of the noise. This was important because I had recently had a similar complaint about the same model set, which turned out to be a noisy power transformer. And I do mean noisy ; it c ould be ' 1: I heard in the next room. It was obviously due to loose laminations but there was little I could do to tighten them. The transformer I is enclosed in a steel . . case, so I simply replaced it under war-.,.,---::-;:_-:::-· ) ranty. .::------_ I After some questionCf-,_:),r1'1 v§r-.". ing on my part as to whether it was a high pitched or low pitched I CP.Rf:FUl-L'-f ?OS I'll ONW sound, and a consulM'-f GOOD E:.P..'R ••. _ And that's the theme of my main story this month. It is about a Samsung colour TV set, a 34cm model (type CB336H), and a fault which is now relatively rare. It was not always so. In the early days of TV, it was a common problem which plagued many a salesman and, in some cases, lost sales. I'm talking, of course, about the high pitched 15,625Hz whistle which emanated from the horizontal output transformer. This whistle was caused by the magnetostriction effect; ie, the physical distortion of the transformer core due to the magnetic field. One problem with this fault is that there are a number of variables which can make it difficult to pin down. Not everyone can hear frequencies this high. In general, young people are more sensitive to it than older people, and women more so than men. The listening position can also be ~~ ex~ it L 51 --- ~nr-z 54 SILICON CHIP tation with her husband, she replied that it was high pitched. And it then transpired that, contrary to the usual rules, it was the husband who found it most annoying, while his wife could hear it only occasionally. I advised her to bring the set in. In the event, there was someone else who had difficulty hearing it yours truly. Age has taken its toll and these tired old ears have not had much to do with that part of the spectrum for some time now. That's not to say that I am totally unaware of the problem, if it exists. I can hear something but I doubt ifit is at 15,625Hz. I think it is more likely that there are some lower frequency components present - sub-harmonics if you like - and they serve the purpose. Initial checks Anyway, when the set arrived I plugged it in and made a preliminary check. Initially, none ofus could hear anything. Then the husband said he could hear it faintly but his wife could not, and neither could I. Then, according to the husband, it vanished but then re-appeared again a few minutes later. I suggested they leave it with me. Later, when I had (literally) a quiet moment, I pulled the back off the set, plugged it in, and let it run for about half an hour. This, according to the husband, was when the whistle was most likely to appear. I then positioned my best ear as close as safely possible to the horizontal transformer. And yes, I could sense something. More importantly, by probing around the area near the transformer, I could make it come and go. So, there seemed little doubt that this was the offender. Nor was there any doubt as to the cure; a new transformer. I've never encountered any satisfactory repair technique for this fault. In any case, the set was under warranty. So a new transformer was ordered, duly arrived and was fitted to the set So what did that leave? As far as I could see, only the side pincushion transformer, T402, which is effectively in series with the deflection coils. My suspicions were further aroused by the fact that this transformer sits close alongside the horizontal output transformer; so close , in fact, as to make it difficult to differentiate between the two on an audible basis. On the other hand, if this was the culprit, it also would be a first in my experience. And that left me wondering ifl could risk replacing it on spec, having already made one mistake with the horizontal output transformer. Technical help And that did seem to fix it. I certainly couldn't hear anything, nor could the husband when he came in to check it at my request. So he tucked the set under his arm and went on his way. Sam still whistles All was quiet - at my end, anyway for about a week. Then the lady was back on the phone. All was not so quiet at her end; the fault was back. As she described it, "the set still does it a bit", although it was not nearly as bad as before. But they were worried that it might get worse. Privately, I was worried too, but suggested that they try it out for a couple more weeks and see what happened. What I really wanted was for it to become bad enough so that there could be no doubts about the problem. And that's more or less what happened. Several weeks went by and then the lady was on the phone again. It was now much worse; in fact, according to her husband, it was as bad as it was originally. So I said, "bring it in and we'll have another look at it". It didn't take me long to confirm their observations, which put me in a bit of a quandary. If it wasn't the horizontal output transformer (two dud units in a row would be too much of a coincidence), then what was it? The diagnosis boiled down to nominating all those components which handled this frequency, then considering each in turn and questioning whether it could be the culprit. My first suspect - but one which I discounted almost immediately - was the horizontal driver transformer, T401. Granted, it handled this frequency but at much too low a level to be a serious candidate. At the other end of the chain was the horizontal deflection coil assembly. Well, there was plenty of energy there but, ifit was the culprit, it would be a first in my experience. In any case, the location was wrong. Even with my limited hearing, I could not reconcile what I heard with these coils; the source was somewhere on the board , near the horizontal output transformer. Finally, I decided to play it safe and tackle the Samsung service department with the problem and my theory. So I rang them and asked for one the technicians who has proved to be helpful in the past. And even while I was describing the problem, I had a feeling that he was way ahead of me. When I eventually asked if my diagnosis was correct, his reply was immediate: "that is the problem. We've had a few of these, but only on the chassis fitted to that model set". (He was alluding to the fact that the same chassis is used in several models, of different sizes and with varying refinements). Just why the fault should occur in only this model is not clear. My tip is that this pincushion transformer is different, either by design or, more likely, nominally the same but from a different manufacturer or even from a different batch. Anyway, that was the solution. A new transformer arrived a couple of days later, I fitted it, and could detect no sign of the trouble. More importantly, neither could the customer, in spite of prolonged observation before he took it away. That was several weeks ago now and, at a recent check, everything is quiet. So make a note of that one and don't write off a customer's complaint just because you can't hear it. The bush serviceman This brings me to the point I made earlier, about sales being lost because TV salesmen did not always understand the problem. It reminded me of an actual incident , in the early days of TV, in which I was involved. It was shortly after TV had started, JUNE 1991 55 SERVICEMAN'S LOG - CTD at a time when the first country services - one commercial station and the ABC - were being set up. At that time , I worked for a sales/service organisation in a large country town. My role was primarily that of a serviceman but there was always the opportunity for a spot of sales work on the side. The reward was a modest but worthwhile commission; a very welcome addition to the regular pay packet. I had scored a few such sales but one family that I had set my sights on were proving hard nuts to crack. They were a nice couple, long standing customers of the firm, and I had come to know them well on the basis of various radio and other appliance repairs. But the expense of a TV set was not something they were prepared to rush into. Against that background, my sales pitch was too much of a soft-sell. It often amounted to nothing more than a half joking, "when are you going to buy that TV set?", which invariably prompted a similarly lighthearted re- OYNAPULSFm 2QOM The DYNAPULSE 200M is an innovative and superior method of monitoring and recording vital personal health information. In conjunction with your PC this unit allows you to measure and map your blood pressure and pulse accurately, as well as printing, graphically displaying and storing your data for later comparisons. PEACE OF MIND FOR: $397.00 ply, "aw, someday". It became a ritual that went on for several months. Then one day, returning from a service job out in the bush, I passed their house on the outskirts of town. They were both in the garden and waved cordially when they saw me. Somehow I sensed it might be a good time to stop and have a yarn - a popular pastime in the country. It was only after I had left the van and was walking towards them that I realised there was a TV antenna on the house. This was a bit of a blow to my ego because it meant that the opposition had scored where I had failed. But that's the luck of the game and I was careful not raise the matter. So we yarned about the weather, its effect on the crops, and the season generally, in the usual way, until the woman said, "would you mind having a look at our TV set. We got it from your opposition but it's driving me up the wall. It has a terrible piecing whistle". Her husband's response was imme- SUPER SPECIAL LUMEN PC MIGHT-25 UPS: The affordable standby powersupply. • Designed specifically to back-up computer systems • Protection against mains brownout and blackout • 250 VA, 240V 50Hz output. • Fully self-contained, automatic operation • Inbuilt mains filtering and o/load protection • Typically 6 minutes backup diate and somewhat spirited. "Ya got whistles on the brain, woman. There's nothing wrong with it". By mutual consent, we ignored him and the lady ushered me inside. She switched on the TV set and we waited for it to warm up. I had a good idea of what to expect but I was a little worried that it might be too subtle for me to be sure about it, although my ears were better tuned to 15,625kHz in those days. But I needn't have worried; the thing was screaming its head off, as bad a case as I had heard. In the circumstances, I had no hesitation in advising the lady that she should insist that the trouble be fixed - or the set replaced if necessary. But no way should she tolerate it. And I gave her some background and a few pointers to let the salesman know she knew what she was talking about. So she thanked me, made me a "cuppa" and I took my leave. It would be wrong to say I didn't think anything more about it, because I was a bit miffed with myself for not doing a better sales job. How to blow a sale It therefore came as complete sur- ANTRIM TOROIDAL TRANSFORMERS THIS MONTH ON.LY: $399.00 FAXGUARO Surges and spikes, induced by lightning or power line faults can destroy your fax or computer. 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BOX 1174 GOSFORD STH NSW 2250 * All products are fully guaranteed • Authorised agent for Critec Aust. • Full range of surge arresting equipment for any application 56 SIUCO N CIIII' • Mail and phone orders welcome • We accept BankCard and VisaCard * I SY A to 62SY A :1vail:1ble ex-stock * I SY A to 2K YA :1v:1 il:1ble to order * Largest ex-stock source of toroids in Au stralia * Competitive pricing available for OEM s and resellers HARBUCH ELECTRONICS PTY LTD 90 George St. HORNSBY NSW 2077 Phone (02)476-5854 Fax (02)476-3231 TETIA TV TIP Hitachi CEP288, CEP289 (PAL3A chassis) Symptom: Reduced height, about 25mm of black at top & bottom of screen. No colour. The picture can recover to normal after 10 minutes but the fault does not appear to be heat sensitive. Cure: C753 (1 00µF/25V electro) open circuit. This capacitor is the input to the filter on the 20V rail and its loss causes the rail voltage to drop, in this case to 14V. The rail shows, no unusual ripple; just a lower than normal voltage. TETIA TV Tip is· supplied by the Tasmanian branch of the Electronic Technicians' Institute ofAustralia. Contact Jim Lawler, 16 Adina St, Geilston Bay, 7015. prise when, a couple of weeks later, the lady phoned and asked me to bring out a TV set for demonstration. Naturally, I had a set loaded and was on my way in nothing flat, but I was very curious as to what had happened. It was only after the set had been installed and running - without any whistles - that I learned the full story. What I hadn't known before was that the opposition's set was only on demonstration; no sale had been made. And, acting on my advice, the lady had made it plain that she wanted the trouble fixed. And that was where the salesman blew it. Whether he couldn't hear the whistle or could hear it but didn't know what to do about it, I don'.'t know. But he insisted, apparently quite curtly, that, "there's nothin' wrong with it". To which the lady replied that, if that was his attitude, he had better take the set away. And here he blew it again. He could still have salvaged the situation by offering another set. But no; he had apparently shifted into "high dudgeon" mode, loaded the set into his van, and gone on his way. Of course, his loss was my gain. The lady and her husband were both delighted with my set and, after a couple days' demonstration, the sale was concluded. So I scored a lot of goodwill for both myself and the firm, plus a very welcome commission. And now, in lighter vein, here's another off-beat story from my southern colleague, J.L., of Tasmania. Why do all the funny stories seem to come from down there? Is it because ... ? Anyway, here's how he tells it. TV TEST EQUIPMENT TO EARN YOU A HIGHER RETURN (Australian Made) SHORTED TURNS TESTER Built-in Meter to check EHT transformers including split diode type, yokes and drive transformers. The reluctant golf buggy Well, now I reckon I've done just about everything in the electronics repair field. A customer came in a week or two back and pleaded with me to repair the "volume control" on his golf buggy. Now this chap is well educated and, over the years I've known him, he's never been known to say something he didn't mean. So I had to believe that he really did have a volume control on his golf buggy and, because it involved electronics, I would have to try to fix it for him. In greater detail, as he explained the set-up, he had a motorised golf buggy and the so-called volume control was actually a speed control. That afternoon, during practise for the next day's championship match, the buggy had dug its wheels in and refused to follow him any more. He fiddled with the control and the buggy made "trying-to-work" noises, but didn't move an inch. He had to drag it around the final holes, and he didn't feel inclined to drag it around 18 holes the next day. So could I please do something about it? He had dismantled the buggy and had brought with him only the handle and the control. He handed me a short length of square section metal tubing with a black cable running through it. On one end of the cable was a 6.5mm stereo phono socket; on the other end, a perfectly conventional 5kQ linear switch pot. It certainly looked as though it should be part of some kind of audio system, hence his description of it as a "volume" control. I used a multimeter to check the 5kQ pot section and it appeared to be OK. Nevertheless, I opened it and checked the condition of the track. It looked perfect so I simply wiped it gently with a soft cloth moistened with contact cleaner, then reassembled it. Unfortunately, the switch part of the device was tightly clamped together and I feared I might not be able $78.00 + $3.00 p&p DEGAUSSING WAND Strong magnetic field, larger than usual coil with multicore centre. Double insulated for your safety, also fitted with momentary on/off switch. 240V A/C 2.2 amps. Just about as important as having a soldering iron in your toolbox! $75.00 + $10.00 p&p HI-VOLTAGE PROBE Built-in meter reads positive or negative 0-50kV. For checking EHT and focus as well as any other Hi-tension voltages. $98.00 + $5.00 p&p REMOTE CONTROL TESTER (INFARED OR ULTRASONIC) Designed to test In fared 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. $85.00 + $4.00 p&p LASER DETECTOR PROBE A new addition to the remote control tester. Comparable with units costing $500 or more. You can test the laser pickup in compact disc players. $27 .00 + $2.00 p&p LOW VOLTAGE PROBE Ideal for checking microwave ovens and TVs. The ranges are from 0 to 5kV Negative and from Oto 10kV Positive. Double insulated for your safety. $84.00 + $5.00 p&p TUNER REPAIRS from $17.00 exchange + p&p Cheque, Money Order, Bankcard or Mastercard -;r-.v. TUNERS) :-:•:•·•:-·-•,:-:-:-:-:-:-:,::::::::•·-· 216 Canterbury Road, Revesby, NSW, AUSTRALIA, 2212 (02) 774 1154 ~~ (02) 774 1154 -a- JUNE 1991 57 SERVICEMAN'S LOG - CTD to refit the cover if I took it to pieces. It was a 2-pole, single throw switch and one pole was wired to the cable. This pole turned out to be faulty, being open circuit most of the time and closing only briefly as the contacts moved from off to on, or vice versa. Fortunately, the other pole was in perfect condition so I merely changed the wiring over to these terminals. I checked the cable for continuity, and the stereo socket for clean and firm contacts. All were in order, so I waited for the customer to return with the buggy. This proved 'to be a fairly conventional type of 2-wheel trolley with straps to hold the golf bag and a single handle with which to guide it. On the axle, to one side, was a surprisingly small DC motor geared to the axle. And on the other side, a battery box about the size one might expect to see on a motor bike. All in all, a most effective way to transport a golf bag. The motor speed control was obviously electronic and was housed in a small box mounted on the motor. The skQ pot was no more than a regulator and on-off switch but, being mechanical, was subject to wear, and it was this that had let the customer down.I haven't heard how he went in the championship match but I'm sure that he had no trouble with his buggy. Just the same, I thought the idea of playing golf was to exercise. Buggy fever But that wasn 't the end of the story. Last week he was back again, not with 58 SILICON CHIP his own buggy, but that of a friend with whom he plays each week. This time he brought the entire outfit, which appeared to have suffered the same fault as his had done earlier. It was a different brand from his but used an identical arrangement of parts and controls. I first tested the switch, which was perfect, then the continuity of the cable down the handle to the stereo socket. This differed a little from his, in that the socket was only a 3.5mm type as opposed to 6.5mm. But there was no problem anywhere to be found. I moved my attention to the short lead attached to the motor control box and, at first, I couldn't see any problem here either. Then I noticed that the tip was missing from the 3.5mm stereo phono plug. I wasn't certain which part of the circuit was involved with the tip, but it was obvious that the system wouldn't work with it broken. So I fitted a new plug. Now, if you ever repair one of these things, don't ever reassemble it on the bench. I made the mistake of reconnecting the battery while the control was switched on and advanced to top speed. The buggy took off along the bench and leapt into space before I could get my brain into gear. Fortunately, its wheels are very resilient and it bounced once', then headed for the door. I caught it before it got clean away, but the experience has taught me to be more wary of golf buggies in the future. I mean, TV sets and video recorders don't take off on their own, do they? It could'a been worse Fair enough J.L., and I'll take good care if ever one of these monsters finds its way onto my bench. But I can't help speculating on the scene had you not caught it. Where would it have finished up? Tearing down the main street, scattering pedestrians and vehicles in all directions? Or perhaps you don't have a main street, and it would have gone bush and never been found. Anyway, thanks again J.L. SC