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Old 7th Dec 2017, 9:23 am   #16
Radio Wrangler
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
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Default Re: Revox A700 flutter only at 7.5ips?

There is a useful amount of moment of inertia in the capstan motor bell, so it will be quite difficult to make it flutter a lot. If this is being caused by the speed servo loop, I'd expect a significant signal at the flutter frequency on the drive to the transistor regulating the power to the motor. A scope would show this.

If the capstan rotation is fluttering through mechanical means, then if the flutter is within the loop bandwidth, you'd see some signal there too as the loop fought the flutter.

Could it be wear in the capstan bearing and at one speed, the capstan exhibits a pronounced wobble?

Flutter in the rest of the tape path may be more likely.

I'm looking forwards to seeing what this one turns out to be.

David
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