Re: ThunderClock Plus

[mjmahon@aol.com (Michael J. Mahon)]

Bill Garber wrote:

>I can set the time and it holds it, but it
>does not run. The time is not incrementing, but it
>will hold the time that I set it at. Very strange
>that it does that much. 

The clock normally runs after the setting software
has done its thing--there is no separate "start"
operation.

This behavior indicates that everything is working except
the oscillator.  There is an external 32kHz crystal and
a couple of small-valued capacitors (around 30pf),
one of them variable, for trimming the frequency.

This hypothesis can be confirmed by probing with
an oscilloscope and a high-impedance probe,
but you can also just try to fix it--not much to lose. ;-)

If there is surface dirt (maybe a transparent film) in
the area of the crystal or its associated printed wiring,
that could keep it from working.  (The crystal circuit is
very high-impedance.)

A light brushing with non-oily alcohol, followed by
a little rinse, should take care of any surface conduction

If that doesn't do it, the crystal may be bad--for example,
it could have been damaged in a fall.

The good news is that 32kHz crystals are almost
literally a dime a dozen--they are in every $1.75
wristwatch, stick-on clock, or old PC motherboard.
You probably have one or more within arm's reach.  ;-)

Now, the bad news--they must be soldered very
quickly and preferably with needlenose pliers for
heatsinking, since you want to keep its frequency
stable.

I'd recommend cutting the leads of the old crystal
with enough left above the board so that tiny crimps
can be made to matching crimps on the new crystal.
Then, while holding each crustal lead with pliers,
quickly "dot" the crimp with a well-tinned soldering iron,
taking only enough time for the solder to wet the crimp.

If the crystal is the problem, that should put it right.

-michael

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