On Mon, 12 Aug 2002, Barry Gershenfeld wrote:

>>Left it on the car dash once and when I came back, the unit
>>was really hot, and the display was completely black.
>>it came back after it cooled off.  And this happened many times
>
>I had a LCD clock that I left on the dash that did that.  It
>worked after it cooled.
>
>Now for my question:  I've had a few LCD clocks that refused
>to work after I replaced the battery.  My guess here is that
>when the battery goes dead the internal circuits stop
>oscillating, putting DC on the display, ruining
>it for the next go.   Believable?

No, the LCD runs on a charge pump driven by the battery (if 1.5V at
least). No clock = no LCD voltage. Much more likely that there is gunk and
dirt in the main board and the oscillator's self bias resistor is not
enough to get it out of its stuck state.

Also some early chips were bad enough that they self destructed in time
(20+ years). I have a freind who collects stuff and I've seen a couple of
strange items.  If unsure scope one of the xtal pins.

Peter

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