Back in the mid 60s I spent one summer between semesters working in a local TV repair shop. There were three of us EE students helping the owner that summer. Each of us had some practical experience with tube electronics, so we were fairly efficient in troubleshooting and repairs.
One day the owner announced a challenge: His landlady had a small “all American five” AM radio that had an annoying noise/oscillation in the audio and he had spent over a week replacing parts and scratching his head. He offered $5 to any of us who could fix it (to save face with his landlady).
I had just a couple of TVs to work on that day, but both the other guys had more on their plates, so I decided to take on the challenge.
I don’t recall if we had any schematic for it (or even the brand), but picked it up anyway.
After “auditioning it” and hearing the annoying noise, I began to think… what hasn’t he changed? Hummm. What about the line cord?
Hey, nothing to lose… so I turned it off, unplugged it, and unsoldered the wire ends, got a replacement, and soldered it in. Then, while I was expecting to hear the dreaded noise again, I plugged it in, turned it on…. and… I heard clean audio.
I tuned the dial… no extra noises. I checked the full range of the volume control… still clean.
I hurried over to the owner’s office and asked him to come out and listen. He couldn’t believe his ears! We probably wasted the next half hour speculating on what the line cord did to create that noise.
I suggested there might be a small break in wiring and the AC was arcing that tiny gap, but we decided enough time had been wasted. I got the $5 and he got his reputation back with his landlady.
Don “Analog” Jones began his EE career with Westinghouse in 1967, Northrop-Grumman acquired them in the mid 90s, so he has been with the “almost same” company for 43 years… still designing electronic circuits.