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 Post subject: Zenith 6s362 Tuner Tension spring adjustment
PostPosted: Sep Thu 16, 2021 2:20 am 
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Joined: Jan Sat 30, 2021 10:52 pm
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Was wondering if anyone has experience on how you set the tension on the clock spring that applies tension to the tuning capacitor? The unit I am working on appears to lock up the tuner. Thanks


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 Post subject: Re: Zenith 6s362 Tuner Tension spring adjustment
PostPosted: Sep Thu 16, 2021 2:28 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: S. Dartmouth MA 02748-1225 USA
The spring is to balance the weight of the rotor so the tuning condenser does not move on its own weight.

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 Post subject: Re: Zenith 6s362 Tuner Tension spring adjustment
PostPosted: Sep Thu 16, 2021 2:34 pm 
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Location: Near Brandon, Iowa
The spring is there to bias the gear train in one direction so that gear train slop is not readily apparent. Later models used the far superior split-gear approach to solve this problem. The "clock spring method" has the inherent problem of winding up at one end of the dial, which can make for a frustrating tuning experience if the spring has been installed with excessive preload.

To set the spring preload, first clean the gear train of all old grease and then lube with light oil. Very little effort should be required to turn the tuning cap with the spring removed. Install the clock spring such that when it is fully wound up at one end of dial pointer travel, its force is just barely insufficient to backdrive the tuning cap.

This is a somewhat twitchy adjustment since there are no real installation metrics, every drive being ever so slightly different for any other identical unit in terms of inherent friction caused by lube condition, wear, dust accumulation and so on. The general idea is to set the spring preload light enough to not allow it to backdrive the mechanism at its "fully wound up" end of travel, but heavy enough to provide some torque bias when the tuner is at its opposite end of travel, when the spring has minimal stored force.


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