OOps! I replied to the sender on this, but meant to hit
the whole list. Maybe someone knows more. So, here
goes..
.........
There are different types of clocks. I'm not sure which
were put in Sunbeams. The type this may be refering to
winds itself with a noticable thunk every few minutes.
Is that what yours does?
If so, here's the deal. When the small spring that
powers the clock has unwound itself enough, a contact is
closed, enabling some sort of electormagnetic device, a
solenoid or something, for just an instant. This is
enough to wind the spring for a few more minutes of
running, when the cycle repeats.
When the battery voltage drops far enough, the available
power is not enough to make the solenoid move when it is
turned on. So it just sits there, drawing current full
time, and heating up. This leads to the eventual
failure of the clock.
It's possible that the instant of normal operation would
not be enough to blow the fuse, but the sustained
operation at low voltage would. A 2 Amp fuse, for
instance, will pass a whole lot more for a few
milliseconds. Most need a fairly large part of a second
above the rated current to blow. There is a small mass
to be heated up and melted, after all.
Rather than a switch which you would forget, you need
some sort of little electronic cutoff that would
disconnect the clock if the voltage dropped below 10V.
Stu brennan
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