Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/3/84; site teddy.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!harvard!talcott!panda!teddy!rdp From: rdp@teddy.UUCP Newsgroups: net.audio Subject: Audio Anecdote of the Message-ID: <1474@teddy.UUCP> Date: Mon, 21-Oct-85 16:07:39 EDT Article-I.D.: teddy.1474 Posted: Mon Oct 21 16:07:39 1985 Date-Received: Wed, 23-Oct-85 07:43:20 EDT Distribution: net Organization: GenRad, Inc., Concord, Mass. Lines: 129 AUDIO ANECDOTE of the (this time it was a week) Way back when I was working in our retail store (about 1974), the search was on for a high-quality line of receivers that would meet our criteria of high-performance, low-distortion, high-reliability, and good manufacturer support. After lots of trials, the new Yamaha line was selected (this was the CR/CA-400, 600, 800, 1000 line). In fact, we turned out to be the first dealer in the Northeast to carry this line, and did quite a bit of legwork to promote and support it. The units were quite good. Typically, they were underrated, power-wise, by nearly 40%, they had vanishingly low distor- tion, good, wide bandwidth amplifiers that were intelligent- ly designed, excellent tuners for the price, and were very pleasing, in their conservative garbs, to look at. The phono preamps had good transient characteristics and were essen- tially overload-proof under all but the most bizarre of con- ditions. We sold quite a few of them. Everybody that bought them loved them. Sure, their was the occasional complaint that the tuner cursor was sticking at times (due to the teflon track becomming unglued at spots) and the ever-present noisy switch now and then, but overall, the customer satisfaction was very, very high. At least for a while, it was. One day, about a 18 months after we started selling the un- its, a customer brought her CR-800 back, complaining (quite apologetically) that there might be something wrong with hers. She was quite unable to articulate exactly what the problem seemed to be, but she settled on an analogy, "It sounds like I live next to Logan Airport". Well, we agreed to look her unit over, and lent her a replacement in the meantime. We set up her receiver with a pair of speakers, and listened. AFter an hour, nothing happened. We gave up went home. Later, a call to the owner revealed that it only happened while playing records. Ok, so we'll listen to records. After another hour or so, still nothing happened. We were about to give up again when everybody got this very frightened look on their faces. The room started shaking. Soon, what sounded like a Boeing 747 on final approach was heard. It seemed like it was but yards away! The roar was deafening! I hur- ridly shut off the speakers bringing relief to all. Into the lab we went, where we set it up again. Looking at the output of the power amp, we saw nothing unusual. Then, looking all the way back to the phono input, again, nothing unusual. The output noise was equivalent to about .8 micro- volts total broadband noise on the input. For a while. After about 2 or 3 minutes, the noise started slowly increasing, then more rapidly. After about another 30 seconds, the ef- fective input noise level was now equivalent to almost 1/2 volt, severely clipping most gain stages after the phone preamp! Well, says us, that's an easy one, just find out which com- ponent is getting noisy with temperature, and replace it. This took one or two blasts of the spray cooler, and a sin- gle NPN signal transistor, a 2SC1345, was found to be the culprit. Wizz bang, out it came, a new one went in, and, presto, problem gone, customer happy, no charge, and Yamaha pays me $24 for 5 minutes work! But, and this would be a truly boring anecdote without a but, the unit came back about a month later, same problem (but different channel). Culprit? A different 2SC1345. Another 5 minutes, another $24 dollars. Boy, says I, this is one way to make a living. Soon, several others brought theirs back with the same prob- lem. I notified Yamaha, and they say they are unfamiliar with the problem. Now, other problems are starting to show up. Tuners are drifting (AFC driver happens to be a 2SC1345), stereo lights don't light up (lamp driver from MPX chip is a 2SC1345). Output stage blows up, taking tweeters with it (bias regulator is 2SC1345). Turntable starts run- ning at erratic speed, sometimes as much as 100 RPM (you guessed it, 2SC1345 is tacho sensor in turntable speed con- trol). I'm replacing 2SC1345's left and right, making a bundle on in-warranty repairs. It turns out that EVERY Yamaha unit we sold with a 2SC1345 somewhere in it came back for repairs. The Yamaha pulls a fast one. They say that they will no longer pay for repeat repairs on units with defective transistors. What this really means is they require repair centers to replace ALL 2SC1345's when the unit comes in for repair. A job that might take 3 to 4 hours on some of the more complex units. And how many repair people will butcher a board replacing upwards of 20 transistors? Interstingly enough, at the same time, Burwen Labs is having a similar problem in their noise reduction units, uncon- trolled noise after warmup. ALL Burwen units eventually had to be repaired. The connection: Both manufacturers were using semiconductor devices manufactured by Hitachi during a certain period of time. It was discovered that there was an impurity in the curing resin for the plastic cases that proved corrosive on the more delicate parts of semiconductor fabrications. I solved the Yamaha problem of not enough money/time to repair by simply sending the whole motherboard or the entire receiver back and let them handle the problem. Interestingly enough, they never officially admitted that this problem ever existed. As an aside, one CR-800 came back, also very noisy, but with different symtoms. Opening the case revealed a white residue covering much of the interior, along with what might have been very minor fire damage in an area that a fire could not have gotten started in (the tone control/tape switch board). I suspected that this was not a warranty repair, and we then questioned the customer. After grueling cross-examination, it turns out he was trying to free-base some coke on the shelf above and ended up spilling the whole mess into his receiver, and nearly burnt his apartment down in the pro- cess! Dick Pierce