Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ukma!tindle
From: tindle@ms.uky.edu (Ken Tindle)
Newsgroups: sci.electronics
Subject: Re: DC motor noise in audio circuit
Message-ID: <15858@s.ms.uky.edu>
Date: 24 Aug 90 13:10:30 GMT
References: <31302@unix.cis.pitt.edu>
Reply-To: tindle@ms.uky.edu (Ken Tindle)
Distribution: na
Organization: U of Kentucky, Mathematical Sciences
Lines: 37

In article <31302@unix.cis.pitt.edu> fmgst@unix.cis.pitt.edu (Filip Gieszczykiewicz) writes:
>	Greetings. 

Greetings to you too.

>	Well, for one, they do keep the motor as far away
>	from the pre-amp as possible. One could shield the
>	pre-amp but that may not work... (well, for me...)

Well, when I layed out the board (which I'm now stuck with) I *did*
keep the head and mic pre-amp section away from the motor.  Now I find
that the pre-amps don't care about the motor, but a line-level op-amp
buffer circuit and the headset power amp *do.*  Not very nice.

I shielded the pre-amps to stop FM radio reception.

>	Oh but the do _do_ something to the motors. Not only are
>	the motors put in a metal container (with rubber vibration
>	"cups" (top and bottom)) but they also wrap the motor with
>	a metal "band". It provides additional shielding.

Well, that's a good description of these motors, except the "band" is
around the transistor speed regulator board inside the motor-

So why is this wonderful shielding not working?  Maybe magic can only
be made by Sharp Corp.?  Do I need to turn Japanese?

>	Take care. (ST:TNG sucks beans! ------+)

"Well, in this case, Captain, I disagree!  One hundred percent!" -
Beverly Crusher, ST:TNG, "Symbiosis".

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INTERNET:tindle@ms.uky.edu | "Could you please continue the petty bickering?
BITNET: tindle@ukma.bitnet |  I find it most intriguing."   ---    Data, 
Ken Tindle - Lexington, KY |  Star Trek, The Next Generation, "Haven"
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