Ghost in the Radio

The first job is always troublesome; especially if you are lucky enough to be given responsibilities which coworkers think is not as per your experience and age.

Those were the days of portable radio receivers and cassette recorders, Televisions was just coming in. Given the responsibility of developing an indigenous TV set with better sound quality available in the market, I spent most of the time breaking-in into other sets. I was not given a dead line as there was much unknowns, I had to send a weekly "What I have learnt" to the Managing Director, who was also the technical head of the R&D.

The R&D cubicle had transparent glass walls, not even curtains. Occasionally people from other divisions would look through the glass, as the inside was darker than the outside, it was a little of a nuisance but one get used to it. Looks were one thing but the discussions, which was unheard for the first three months came through corporate grapevines to the MD and one day I found myself scheduled for an after-office-hour meeting with him.

The first thing he mentioned was that I should go through the radio, audio products, evaluate performance, give technical service to the service department and also give weekly one hour lessons on hardware debugging.

This was a little puzzling; deciphering the innards of the Television sets took up all of my time. There were specialists on every products of the company; they had five to ten years of experience in their respective fields. Anyway, I had no choice.

After the official notice, every Saturday forenoon these veterans clustered in the meeting room with technical problems, since I understood schematics better I somehow managed not to make a total idiot of myself.

But the problems began to get harder day by day. Ultimately, I had a big stack of problems on my table, begging to be solved. These products are out there in the market in hundreds and thousands but the ones on my table have some bugs making them fail within warranty period.

Working overtime and comparing similar circuits, slowly the stack of problems began to come down and I found out why the MD in his wisdom gave me this job. To earn the technical respect of the people who used to stare at me thinking -what that boy was doing sitting, sitting ideally over a single piece of paper day in and day out?

He succeeded in his strategy. However, I failed on one person of the radio department. He was the head of the radio service department for fifteen years. He knew the deceases of all the models by heart. All the problems he gave me took a lot of time to solve, but by his looks it seemed he still had a secret weapon, a one-shot knock-out for this young up-start.

One morning he waddled into my room, in his hand a radio receiver. By the looks in his eye and the smile on quite a pleasant face, I knew my omega point has come.

"This set has a strange problem, the model is one of the most successful one in the market. Yet for the last two years most of the sets comes back with the same problem, in the medium wave AM band, at frequencies above 1.2MHz the reception becomes poor, and tuning becomes very difficult during the nighttime. If I re-tune the coils, reception is better, but then daytime reception is affected. The problem is solved if new coils are inserted. But the problem reoccurs again after a few months."

With this, he dumped the set and the schematic on my table. "There is no hurry; I know it will take some time, if at all you....ah, it can be solved".

This was a puzzle with a hint; if the set becomes OK night and day by changing the IF coils then something must be wrong with the coils itself. The super-hetero dyne mechanism mixes a local oscillator frequency with the tuned-in RF frequency in such a way that the difference of the two frequencies is about 455Khz, This is called IF or intermediate frequency. This single frequency is amplified in three stages by tuned,band pass amplifiers.

The band pass frequency was dependent heavily on the coils and associated capacitors. The dumped set had the same problem. In the day time there was normal reception but during the night when I took it home the reception of frequencies above 1 MHz was very bad. I did not change the coils, at that time, we had no good high frequency LCR meters, definitely, the coil inductance or the small capacitance was changing, but what it has to do with night and day, heat had little effect, I ensured that.

I used to carry the thing in a plastic packet. When a series of natural holidays was forthcoming, I concatenated those with my leaves due, took the packaged receiver, my haversack and vanished from the world of technology.

After about twelve days when I returned home, I found that I had completely forgotten about the packaged troublemaker. As soon I unpacked it, a strange smell was in the air, there was no battery, where it is coming from.

The smell disappeared quickly but I decided to take out the metallic cover of the first Coil, the most sensitive one. after taking out the cover I turned the set upside down to de-solder the capacitor, but then decided I will rather do it in the office, I had the set upside down on a clean sheet of brown paper, when I was about to put back the paper I saw some whitish substance on it. On finer examination with homemade microscope, I was in no better position.

Across my office there was shop selling college lab equipment, I took the thing there and asked if I can see the substance through the compound microscope, that was on display. The old shop owner became very interested, as he knew I was working for the big company just opposite to his shop, he let me borrow a microscope on the condition he will come himself and take it back at 5 PM that evening.

Back in my room I found that the whitish dirt looked like spores, organic definitely, not paint or varnish, I carried on after 5 PM, but the shop owner did not come, the shop closes at 7, so I decided to take a last look and return the microscope myself. This time when I looked I found that the white dirt looked wet, soggy. On the thin tissue paper on which I kept them there seemed to be an imprint of wetness.

Next day I cleaned each of the coils with Ether. Heated each coil and varnished them with standard varnish. The problem was gone forever.

Humidity dirt and heat, they are the greatest enemies of electronic devices. It was the the respiration of the fungus, which was alcoholic in nature that was causing the problem.

The coils was hand made in dirty room of a supplier, somewhere in Assam, India, a place with high relative humidity on the average. The Fungus was dormant but after sundown, it used to secrete the liquid, which changed the Q value of the coil and therefore the trouble

In human beings fungus causes Athlete foot,Thrush. Of course there are different varieties of Fungus. One variety of fungus attacks the anti-reflection coating of the lenses of the camera. Nowadays Inductor coils are hermetically sealed. Generally Fungus prefer warm,damp and dark places.

My Biological tour to find the ghost in the radio set is a lesson emphasizing a point in troubleshooting.

Before you are exhausted by using all known methods to find the solution to a problem,do a background research of the part-manufacturer of the components under suspect.

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