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.

"cropduster" wrote in message
...
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.


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.

cropduster wrote:

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

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.