Michael Lawson wrote:
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.
Do a net search on "eletro-migration".
Over time the electrons carry some of the ions that make
junctions either P or N. Electro-migration increases with heat,
I think it doubles for every 3C degree increase. This is why
overclocking CPUs cn lead to unexpected failures.
So, does that mean it might not be a bad idea to
do some restoration work (or have it done) on
the newer radios when they reach 20 years or so,
sort of like the older tube radios?? I imagine that
the caps last longer than the old paper caps or black
beauties, but fixing up an R-70 or an FRG-7700 (if
in otherwise decent shape) hadn't occured to me before.
You can't restore ICs, of course, but you can replace auxilary
transistors, capacitors, resistors, etc. I know that some of the older
transistorized clock radios (the ones made in Japan prior to the
microchip age) tended to have the radio die gradually over time. This
happened prior to the motor which flipped the numbers dying. I know that
happened to an old 1971 Juliette which was my first radio. The radio
gradually got weaker and weaker and finally went silent, then the
numbers stopped turning. Those clock radios were pretty cheaply made and
were not worth restoring, but a tabletop SW radio like a 7700 would
definitely be worth restoring if it was otherwise pretty good.
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