Sherlock Ohms: Corroded Copper Stops Dial Tone

Immediately upon seeing the title of this newest Sherlock Ohms adventure, I thought of my own experience with a telephone dial tone problem. In A. David Boccuti's case the culprit turned out to have an entirely different cause than mine. Read about Mr. Boccuti's issue resolution here. My dial tone dilemma was caused by corrosion as well, but mine was inside the phone itself. Being a lifelong avid fan of Charles Schulz's Peanuts comic strip, I decided to purchase a 1976 vintage Snoopy and Woodstock telephone from someone on eBay. It was promoted as being in working condition, but I discovered 'working' was a subjective term in this case. Indeed, it was possible to hold a conversation, but the volume in the earpiece was very low, and the dial tone was weak and intermittent. I have a more detailed description of the problem and resolution on my AirplanesAndRockets.com hobby website, but to make a long story short, it ended up being a two-fold cause. One offender was a dirty switch contact on the keypad assembly and the other was a bad diode in a polarity correction circuit at the input to the network block. This would be a great addition to my new Out of Order feature, but it's already been covered. Maybe I'll recount the story there at a later date after everyone has forgotten about it.

Posted  February 11, 2014