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How to correct the chime and strike on a Seth Thomas Sonora chime clock

11/9/2015

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If you have a Seth Thomas clock that chimes, there is a chance that it is one of their "Sonora" models. These can be distinguished by looking inside of the clock. You will see what looks to be not one, but TWO clock mechanisms within your clock. In reality, one movement (behind the dial) controls the clock and the hour strike. The other movement (near the back of the clock) controls the chime that plays on the quarter hours.

It's an ingenious design. With the addition of the independent chiming mechanism, this system allowed Seth Thomas to reuse simple striking clock movements and sell them as chiming clocks. The down side? If the chime gets out-of-sync with what the hands say, this model of clock has no means to correct itself. That job is up to you.  Here's how it is done.

There are two levers coming out of the back of the main clock movement (the one located behind the clock dial). The upper lever (A) will trigger the the hour strike. The lower lever (B) will trip the quarter chime.
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The Seth Thomas "Sonora" chime clock movements, as seen through the back of a clock.
IIf your clock is striking the wrong hour, momentarily press down on the upper lever (A) to trigger the strike. Repeat until the clock has reached the desired hour. If you need to correct the chime too, you might want to stop at the hour before the one desired (see below).

If your clock is striking the wrong part of the chime tune, lift up and drop the lower lever (B) to trigger the chime. It should play 4 notes at quarter past, 8 notes at the half hour, 12 notes at quarter of, and 16 notes on the hour. Once it has finished playing the full chime on the hour, this mechanism will then push on the strike lever (A) one time on its own to trigger the strike. The two mechanisms are playing tag with each other. On the hour, the clock tells the chime to mechanism to start. The chime mechanism plays, then finishes up by telling the main mechanism to strike.

Often, it is convenient to move the hands to the top of the hour (allowing the clock to chime at each quarter), then go about correcting the chime, allowing it to play the full 16 note tune. Finally, advance the strike using the upper lever until your reach right number of blows for the hour shown on the dial.

-Dug North, Clock Repairer
www.ClockFix.com

9 Comments
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    Clock Repairer Dug North

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    Dug North repairs antique clocks in and around Lowell, Massachusetts. He's also known for his mechanical wooden sculptures.

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