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SOUTH ELECTR )))). 0-----------------• money. But those of you who've brought back a bomb from overseas know how hard it is to get service, much less warranty repairs. John wanted to give everyone a fair go; even passing tourists he'd probably never see again. Although we on government contracts were I • • assumed to be 24-hour-a-day b employees, the rule was more ~ 0 _: honoured in the breach. So I spent ,!, I\,./ l five or six hours a week when off• 'O tl duty, checking amps and cassette decks and the like . •• • t>• .. • I"""- ,. What do the natives do when their electronic organ fails? Call a serviceman of course. But the serviceman can get more than he bargained for. By J.L. ELKHORNE "How are you on organs?" I looked bemusedly at the telephone handset; I'd always wondered what an obscene phone call sounded like. After a moment's pause, the voice continued: ''Hello, hello, are you there?" There was silence for a second. Then: "Joe, is that you?" Now I recognised the voice. Not a phone phreak after all, but a New Zealand bloke who ran a big duty-free shop on the South Pacific island where we had lived for two years. In addition to providing genuine bargains for the tourists, he worked 50 SILICON CHIP up a thriving trade with the indigenous population and the hundreds of contract workers that were temporary strangers in paradise. Unlike some of his counterparts in the "civilised" world, John insisted that every piece of electronic gear be subject to a real quality control test before it was sold. One Japanese manufacturer averaged 40% failure rate right out of the export cartons; their quality assurance tags didn't mean much! Once the bugs were found (and they were generally minor) the equipment proved itself value for The job The telephone call I'd just received, on my day off, seemed to be an intrusion into my plans for scubadiving. It was not an emergency call, however; immediate action was not necessary, but there was a big problem. John had sold a large organ to the villagers on an adjoining island. These industrious and thrifty people had saved for seven years to purchase an instrument suitable for their church. It had worked splendidly for the first few weeks. Now, it seemed, there was not a peep out of it. A bit of service information had come from the manufacturer, and I had a fairly complete service kit and test equipment. But, in itself, getting to Manua (part of American Samoa) was the hard part. A supply boat made the trip once a week. It had left yesterday. There were a couple of flights by a Fokker Islander; if the seats weren't filled with passengers, excess cargo was thrown in. More than once, a small pig was admitted on board, even if he didn't pay full fare. John arranged that I should go to the airport on Tuesday of the next week. I was given the name of a villager who would escort me, since after the flight. there was still the PACIFIC: 'IHE OMC VERSION little matter of an hour's drive to the village itself - somewhere. With eager anticipation, I arrived at the airport as arranged. And waited. Long after the Fokker had climbed into the azure sky, I stood there. I even tried to call my part-time employer but the phones were out. That wasn't unusual - if the phones weren't dead, other public services would likely be impaired on our tropical paradise. The local power operators frequently put a generator on-line unphased - or tried to. Grumbling more than a little, I drove to the duty-free shop. John seemed surprised to see me. When I told him that the villager had been a no-show, he sent one of his lads out to find the bloke. When they located him, it took three days for him to dry out. Getting over to the 'big island' was quite a treat for him; it happened so seldom he wanted to make the most of it. Out from under the eyes of the village elders and the minister, our hero found the native version wine, women and song. The flight Several days after the first attempt, we managed to get underway. I'd never flown from our island in a small airplane before. It was different. The gusty crosswinds didn't seem to bother our pilot. I glanced at the Rolls Royce nameplate on the port engine for reassurance. I recalled that the last flying accident here had been ari aircraft stalling at the end of the runway and dropping onto the reef. But Snoopy powered us into the sky and, in a few minutes, we levelled off a hove the ocean. The afternoon sun bored in through the perspex windows; the drone of the two engines lulled one into a lethargic state. Surprise! One minute a person saw, despite drooping eyelids, the cobalt of the Pacific. Then, all at once, a sheer cliff of rocks and foliage soared up to the belly of the Fokker. There wasn't even time for one's life to flash before his eyes! My reaction must have given quite some amusement to the other passengers. They knew the airstrip had been bulldozed off the side of the mountain. The pilot simply took off and reached his flight altitude. He didn't even have to make a descent to land; he just took careful aim, throttled down and hit the binders. The Fokker came to a shuddering halt one metre from a wall of jungle. We got out with some haste, and a couple of husky fellows helped the pilot turn the plane around. My guide said, "There's our people". The Land Rover I turned to see three natives leaning on a vintage Land Rover. We picked up our parcels and went to meet them. After lengthy introductions, our drive began. And went on and on. It wouldn't have been unpleasant - what with the lush scenery - except for the fact that the supports on the hardtop had rusted and the passengers had to hold the damned thing together. It took some 45 minutes to make the side trip to my escort's £ale (village house). I couldn't exactly understand the driver's parting words to him, but I got the impression the poor fellow wouldn't be getting off Manua for quite some time thereafter. Eventually, we arrived at the village. The driver led me to the village elders and ritual introductions were exchanged. One had to move at their pace, of course; it was no use being impatient to get started with the job I had come for. But these people were impatient, too, to hear the majestic tones of their expensive instrument. ----------- SOR"R.'11 'BIGt-P\~S f>A'1 FULL f'A"R.~ ••• - - - - - ~ r··.- . . FEBRUARY1988 51 My surprise was indeed great when I was led to a large open fale. This is the classic structure of the islands, of course. Why I should have expected a conventional church, I can't imagine. Inside, on the woven grass mats - well away from the open side walls - sat a large bulky tarpaulin-wrapped object. To be sure, a fale has woven curtains that can be controlled at the sides, to keep out most of the rain ... when someone remembers. The tarp was used for added protection. It also ensured the containment of the wonderful 90% relative humidity salt air. I dreaded what I would see when this mummy was unwrapped. Fortunately, it was not too bad. Someone found an extension cord. Of course they had electricity - US surplus military generators have to go somewhere! I plugged the instrument in and turned it on gingerly. The power light came on. I tried both manuals, the pedals, several stops. Nothing. At least I had been spared an intermittent fault. Or an instrument that was three-quarters right but with irregular voicing faults, or some such. [Bear in mind that I had never worked on a large organ before but electrons is electrons). In a trice, I whipped the back off. Previous study of the available service information had paid off. I had a fair idea of the circuit flow - all I needed initially was to find the damned modules. Luckily, the power supply was screwed to the bottom of the console where it was easy to get at and the plug-in preregulator lived next to it. Begin at the beginning I told myself. Yes, of course there is AC in and DC out. No inordinate amount of hum. On to the the pre-regulator connector. Unregulated voltage in and naught out. Eureka! On to the circuit board. Hey, this is going well. The circuit used discrete components - with the spares I carried, there would be no problem, I reckoned. I thought I must have shaken something up when my trusty analog meter told me that there was good regulated voltage right through the PCB to the edge connector. Walking around the organ, I reached out and tapped a couple of keys. Then my foot nudged a pedal. Nothing at all. Curiouser and curiouser. Back at the back I picked a board at random and looked for the supply rail. No rail. I then used my meter on the amps scale to bridge the edge connector of the preregulator. Nothing blew up Tt\\S l S "<OU~ ES~-C-: and I got ~ reasonable > current readmg. VJ \-\0 W \ \.-l- GU l'DE" '{ 0 U Around to the front and SA.i='E.L"f TO '{0\)~ a stroke on the keyboard elicited a nice full note 'DE.STH,JP\T IOl'J, o, and an "Ahhh!" from the \ '\ onlookers. Every time I ~\~~ ~~ looked up, I saw more peo~ C ~~~~;> ple. By the time repairs <at> ,;::;;; •. . . ~-::;,_were completed, virtually · • lj ~ the whole village was -=watching. ~ Cutting the power o and pulling the preregulator, I saw the signs of corrosion on the contacts. A minute's work with a typing eraser and 52 SILICON CHIP aerosol spray solved the problem that had brought me on my adventure. Not that it had ended. I powered up and checked several things in the works. I tested stops and all keys and pedals. Everything seemed "go" so I buttoned it up. The music I went to the head man and told him it was finished. "No!" he responded. A short conference with the driver as translator indicated that while it made sounds, it hadn't made music. "You know about the organ, so play it," the head man was saying. "I know about the organ to fix it," I told him. The elder fixed me with a steely gaze and mumbled something to the driver who mumbled and said, "We must have some music before the chief is satisfied". Fortunately, many years before, I had studied piano [thanks Mum), even into university. Though a habit of playing jazz put paid to a glorious career in the concert halls, a knowledge of music certainly seemed worthwhile at the present moment. "Unfortunately, I don't think I know any hymns," I said, glancing at the band of people around me. The driver conveyed this to the chief, who shrugged and muttered a terse reply. "Is not Sunday," the driver translated. I'm not sure if any of those people ever had heard of Fats Waller but they sure seemed to enjoy "Ain't Misbehavin"' and other of his classics. Every time I stopped playing, someone said, "More!" Well, if I could get away with Waller, a bit of Jelly Roll Morton never harmed anyone. Next followed Cole Porter and it still wasn't enough. I switched tactics. A bit of my formal training came to the rescue and a free-form version of J.S. Bach's "Toccata and Fugue in D Minor" nearly took the thatched roof of the £ale. Phantom of the Opera, eat your heart out! When the last note died away, I raised my hands from the keyboard and dusted them symbolically. "Uma lava pisupo," I stated. Which continued on page 65 SERVICE.MAN'S LOG found that all was well up to these points. But that was as far as it went; there was virtually no signal on any of the collectors. And since it was unlikely that all three transistors had failed simultaneously, it just had to be a voltage problem. A clue at last The voltage on these collectors is supposed to be around 125V but the best I could find was a mere 12V; small wonder we had nothing on the screen. But at least I had a clue to one of the faults - all I had to do now was find where this voltage originated and why it wasn't being supplied. Unfortunately, it is not practical to reproduce the circuit since it would be far too large to encompass all the points involved. In brief, however, the collector voltages are derived via 10k0 load resistors from a common 160V supply line. This line leaves the neck board at "Yl ", goes to pin 3 of socket C0-2S, and then to plug C0-2P on the horizontal scan board. (This plug and socket pair are separated by nearly the width of the circuit). From here the line follows a rather circuitous route to the vicinity of the horizontal output transformer, and pin 6-2 of this transformer in particular. In greater detail, this rail is derived from pin 6-2 via a 3.30 resistor, a small choke, a diode D553, and a lOµF 250V electrolytic filter capacitor, C564. Naturally, these few components were prime suspects although I couldn't rule out that a fault somewhere else was loading the line. The choke and resistor were quickly cleared, then I lifted one end of diode D553 and checked it. But the diode checked OK, leaving only the electrolytic capacitor (C564). I pulled the electro out and measured it. And that was it; instead of the supposed lOµF the best it could manage was a mere .OlµF. Well, at least I had solved one problem; replace the capacitor and I should have a picture on the screen, even if it was squashed. Then I could concentrate on the scan fault. So the electro was replaced and I switched on hopefully. And sure enough, up came a picture in full colour. But that wasn't all; all the other faults had vanished as well. The picture was back to normal height, the brightness and contrast controls were functioning correctly, and the distortion had vanished from the sound. All with one capacitor. Naturally, I was both delighted and surprised; delighted because I didn't have to look for any more faults and surprised because I hadn't realised the full ramifica- Servicing in the South Pacific literally translates as "The pea soup is finished," but really conveys finality. Cross-cultural relationships create some interesting language. Having acquitted myself of that sticky situation, I now found I had to face the honour of a meal. Four serving girls brought a number of curious dishes - which I alone ate in the centre of a throng of people, all eyes on me. Perhaps to see if I would refuse their food? Not likely, mate. For one who has shared unnamed delicacies in Saudi Arabia, few culinary surprises are left. continued from p52 I'm not sure, but I think they then made me an honorary member of the village. Suddenly, the driver realised how late it was and shouted, "The plane, the plane!" Bidding the people a fond and hasty farewell, we raced to the Land Rover - which no longer had its insecure hardtop. If that driver ever comes to Australia, he could have the pole position at the Adelaide Grand Prix, no risk! With not a moment to spare, we screeched to a stop at the airstrip. Lo, the Fokker was already revving its engines. I raced to the port side and tions of the 160V rail. I reached for the circuit again and indulged in a spot more tracing. Not surprisingly, I found that this rail also supplies the vertical oscillator circuit or, rather, part of it. As I mentioned earlier, this stage consists of two transistors, TR402 and TR403, employing a fairly straightforward feedback arrangement. But TR402 is fed from a 24V rail, while TR403 is fed from the 160V rail via the height control. Apparently, the 12V I found on the 160V rail was sufficient to keep the stage oscillating, but at a reduced amplitude. This aspect puzzled me somewhat because the waveform checks I had made, while not perfect, had not been all that far out. Then I looked at the circuit again and realised that the waveforms shown, and which I had checked, were all associated with TR402, which was functioning more or less normally from the 24V rail. The only remaining puzzle concerns the sound fault. I can find no direct relationship between the 160V rail and the sound system. The sound IC, IC251, appears to derive its supply from the commutator section on the deflection board and I have not been able to relate this to the 160V rail. Unfortunately, there is a limit to the time one can spend trying to work out all the smart tricks the designers pull. For the present, I am happy to accept that the fault has been cured, even if I'm not quite sure why. ~ threw myself into a seat as the craft started down the strip. If landing was a shock, the takeoff was a real thrill. At maximum revs, it was as though the island fell away under us. As I stared down at the blue Pacific, I noticed that one of my meter leads was caught in the door. The slipstream knocked it about until it frayed apart and dropped far down to the ocean beneath us. As we drew closer to the big island, I reflected that the life of a field service engineer holds many surprises - and that technical knowledge is often the least of your worries. ~ FEBRUARY1988 65