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#11
March 8th 05, 03:18 PM
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wrote in message ups.com... wrote: My wife and son are both E.E.'s and their explanation is that IC's begin to degrade slowly as a result of impurituies in the wafer. Simple components like capacitors dry out and resistors begin to open up. Wish I knew more, but I can hear what they tell me in the radios I've owned. I owned one of the comparison radios, the Panasonic RF5000b. Big beast of a 24 pound radio with four antennas. It was pretty insensitive by any measure. Sure it would catch the big nighttime SW's but that was about it. Other radios, such as a Radio Shack DX150b were still pretty sensitive (and still raspy sounding) after 25 years, so the rate of degradation isn't a constant. I'm not an EE, but I do fix electronics as a hobby. In my experience, degraded (but not totally dead) ICs or transistors are among the least likely failures and failed semiconductors are almost always caused by exposure to excess voltage such as static discharge or funky power supplies, reversed voltage or drawing excess current through them. Spilled liquids can be a menace. Bigger problems are poor solder joints, dried up electrolytics, cracked circuit boards, drifted carbon composition resistors and home handyman alignments. If you're looking for esoteric failure modes, don't forget tin whiskers. Tin plated conductors, such as the leads on most IC packs, can grow fine whiskers from the tin plated leads which might short out adjacent pins. The most likely parts to fail on tube radios are paper capacitors, electrolytic capacitors and carbon comp resistors. Tubes age as well, but they're usually OK. Frank Dresser |
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