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Re: [Amps] Shaded-pole Tube Blower

To: "Harold B. Mandel" <>
Subject: Re: [Amps] Shaded-pole Tube Blower
From: R.Measures <>
Date: Sun, 21 Nov 2004 00:12:21 -0800
List-post: <>

On Nov 20, 2004, at 3:10 PM, Harold B. Mandel wrote:

Pat Stein at Commander Amplifiers readily admitted that the Dayton 4C761
shaded pole turntable-type blower motors run very hot in the Commander
amplifiers, like 180 to 200 degrees F.

Dayton motors are a big advantage on Antarctic DX-peditions.

One of the fresh air inlet grates is directly below the fan motor so there is some
cool air going across the motor body.

I didn't find any lint or debris in the bronze bushings and there was some oil
still floating around and the armature spun freely. I can't imagine why the fan
refused to start other than in the new series of Commander amps the fan motor
is on the soft-start circuit AND has a 75 ohm resistor in series with one
of the fan motor leads (that is shorted out for a fan speed increase in

Since the technical information about shaded pole motors does say they are
hard to start, I wonder if the combination of series resistance and
soft-start circuitry sometimes prevented the motor from starting?

Hal -- My SB-220 fan's shaded-pole motor has a 75-ohm resistor in series with it when the exhaust air-temp is cool. When the air gets hot, the 75-ohm R is shorted by a thermostat to speed up the fan. There has never been a problem with the motor not starting,

... ...
Richard L. Measures, AG6K, 805.386.3734.

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