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Servicemans Log

Sometimes, it's a good idea to keep quiet about certain jobs, especially when the other party is in a position to return a favour. Such was the case in the middle of England's winter of discontent.

by the Serviceman

Items Covered This Month

• Jim’s induction heater

• Goin’ nuclear

• 1950 Philips Radioplayer 124

• 1965 Hacker Sovereign RP18 multi-band AM/FM radio

My first story this month comes from D. D. of Coogee, NSW and concerns a very unusual fault in, of all things, an induction heater. Here’s the story in his own words . . .

Many moons ago, when I was much younger than now, I started work in the chemistry department of an English redbrick university. I was a brand new graduate from a university in a nearby town and I think that the main reason I got the job was that the two new professors who interviewed me were originally from the university where I studied and had only recently moved.

I was employed to set up an electronics workshop, which I thought sounded quite grand but things were not quite what they seemed. I knew all sorts of “useless” things like the energy distribution of electrons in common semiconductors and I could calculate the currents and voltages along a twin-wire transmission line using the exponential form of complex numbers. But as to anything practical, well you just had to “learn on the job”.

It soon became apparent that the main reason I was hired was that it was much cheaper to have me service all the expensive electronic equipment, rather than call in service personnel from the manufacturers. I did learn on the job and like “The Serviceman”, have had many interesting and humorous experiences.

Jim’s induction heater

One morning, while sitting in my workshop wondering what I was doing here, the phone rang. It was Jim the glassblower.

Now Jim was one of those old-fashioned characters, a real gentleman and very skilled at his craft but he didn’t trust electricity. “I mean, you can’t even see it”, he would say, “how can all those electrons fit in that tiny wire – it beats me”.

Click for larger image

I used to try to reassure him that everything could be explained but he was far from convinced.

Anyway, on this particular winter morning Jim was really spooked. “Dave, can you come to the glassblowing workshop straight away? I’ve just got in and something very strange is happening”. So I donned my white lab coat and grabbed my trusty AVO meter and headed off.

When I got there, Jim met me at the door, grabbed my arm and said “look”, pointing at his brand new induction heater, “I haven’t even turned the power on yet”. So what was wrong?

Well, as with all the university’s rooms, there was a distribution board with circuit breakers and a main switch just inside the door. Jim ALWAYS tuned the power off before leaving so he was completely freaked out to see the power indicator light glowing brightly.

I must admit I was a little perplexed as well but I told myself to approach this logically, so I checked and indeed the power was off. Next, we cautiously approached the machine. It was a fairly big box, about 1m high by perhaps 75cm wide, with a perforated metal back and sides. It was basically a big RF oscillator with dials to set frequency and power and a metal ring protruding from the front panel.

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