"John Blake" wrote in message
:
John Blake wrote:

Any ideas what might have gone wrong in reassembling a Casio F-91W
digital watch (or similar) after a 3-V cell change that's making the
audio transducer inaudible? The LCD lamp-button works, as do other
setting buttons.

The alarm works, dislaying a blinking LCD symbol when it activates, but
no beeping sound. THe usual beep when changing modes is also missing.
I'd like to know what to look for if I take it apart again.

Thanks for your tips.

John


Many thanks for the replies. Don't think I
left out a spring.

These springs are usually quite tiny and can fly out as the back is removed,
in which case you might never have had a chance to see it!

But there was a bent-up
tab on the back plate (not the screw-on rear
case plate), located just above a tiny
metallic cylinder that I suspected might be
the transducer.

The metallic cylinder is probably the quartz crystal, the watch's main
timekeeping component. The "transducer" is usually a thin piezoelectric
element laminated directly to the inner side of the case back. There will
typically be a dull silver-colored conductive coating on the surface, which
shows marks readily. If the case back has been removed and replaced properly
a few times, there should be an obvious place where electrical contact was
made. Also, there must be a second connection to this piezo element through
the case back itself, which may be made near an edge away from the element, or
with metal-cased watches, via the case.

Initially I tried installing the back plate
180 degrees twisted until I saw the the
Casio's 3 push buttons didn't match the three
grooves on the watch 'chassis'.

Also, the original cell had a tiny piece of
black insulating tape on it (sticky both
sides), located just above the transducer. I
didn't put any replacement tape on the new
cell, thinking it might have been just to
hold the cell still during assembly. The back
of the watch chassis had a piece of white
tape on its back, and I substituted clear
Scotch tape when I reassembled it.
John

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Alan "A.J." Franzman

Email: a.j.franzman at verizon dot net

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