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Electronics Forum / Repair / July 2009Scott 558T AM/FM tuner - no longer remembers station presets
Before AT&T shuts off my Usenet access, I'll get in my one last question and hopefully someone can help. Scott 558T digital AM/FM tuner, bought in October of 1983 but probably built a year or two before. It doesn't remember station presets anymore when switched off. I looked inside briefly for a coin cell battery or large capacitor but nothing caught my attention. How did digital electronics of this age remember things when switched off? Thanks all. > Before AT&T shuts off my Usenet access, I'll get in my > one last question and hopefully someone can help. [quoted text clipped - 7 lines] > > Thanks all. Usually a backup capacitor. Probably physically near the control microprocessor. Maybe on the front panel under a display tube for example. I'm losing usenet through ATT as well, but I have another binary server I can use. Hopefully they do a little better job of filtering the spam. Mark Z. > Scott 558T digital AM/FM tuner, bought in October of 1983 > but probably built a year or two before. It doesn't remember > station presets anymore when switched off. I looked inside > briefly for a coin cell battery or large capacitor but > nothing caught my attention. How did digital electronics of > this age remember things when switched off? I don't know anything about that Scott tuner but a lot of stuff designed in the early 80's used these serial eeproms like an 93c46. It's a 8 pin dip (usually) and was fairly simple to use and incorporate into a design. Most were only a half k or 1K in size but was more than enough to hold a table of stations or other settings. They were used in many products including alarm panels, car radios and various other consumer electronics that were "cutting edge". They did not last forever. There was a lifespan to them, read cycles were in the 100's of thousands but write cycles were in the low thousands. There might of been a general lifespan in years too. -bruce bje@ripco.com I have a Lux 5T50 from 1977. It used a small nicad battery recharged when the unit was turned on. The memory lasted a few days. I later installed a 5V power supply that was on as long as the unit was plugged in. That was later replaced with a supercap. You might look for a small nicad battery. There has to be /something/, but you'll probably have to look closely and patiently. |
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