Ben:
I do not understand why an original clock could be polarity
sensitive. There are no transistors or ICs. The electrical
system consists of a small magnet (bobbin) and a make and break
switch which is part of the balance wheel. Transistorizing the
clock does make it polarity sensitive. The only reason I can
think that is MAY BE polarity senstive is the direction of the
current across the switch contacts causes greater burning of
them.
In standard form a full twelve volts passes between the steel
contact pin on the balance wheel, and the tungsten contact
mounted on a pivot. You can actually see the spark. This
voltage and the constant rubbing eventually causes the steel
contact pin to burn through. The arcing also causes oxides to
build up on the contacts which decreases the current flow enough
to cause the clock to stop. The transistor greatly reduces the
voltage and the contacts don't arc and burn through or stop
because of contact resistance. I fused the clock on my TD before
I had put the transistor in it. When the car wasn't being used,
I just pulled the fuse.
Blake
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