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From: root@ninja.dell.com (Randy Davis)
Newsgroups: rec.audio,sci.electronics
Subject: Re: My CD player is running slow! (Correction)
Summary: Tape players move the tape at constant speed...
Message-ID: <6042@uudell.dell.com>
Date: 5 Jun 90 17:34:52 GMT
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In article <6382.266ac585@umiami.miami.edu> chuck@umiami.miami.edu writes:
|                                                    ..... I would rely on 
|the pitch of a CD over the pitch of a tape deck any day, especially since 
|the tape speed varies over the length of the tape, and the fact that the CD 
|player is (supposed to be) accurate to 1/44100 of a second.

  A nitpick:  Tape speed DOES NOT vary over the length of the tape in a
properly operating tape player, that's the purpose in life for the capstan
and pinch roller.  Tape speed is normally changable by adjusting the
potentiometer on the pinch roller motor control board.  On those decks, most
of them, that use a single motor, this is not too hard to find.  On those with
multiple motors, one needs to find the motor that drives the capstan/pinch
roller (normally the motor is connected to the pinch roller, and the capstan
- the roller that is wide and covered with some friction material - is simply
a passive component), and adjust the speed of this motor.

  In all the tape players I have seen, the take up reel is run at some high
speed (higher than normal tape transport speed) that can easily pulled down
to a lower speed by sufficient resistance.  This resistance is supplied
by the capstan/pinch roller regulating the speed - the take-up reel is trying
to turn at a higher speed and keeps tension on the tape from the capstan/pinch
roller to the take-up reel.  At the same time, the supply reel is kept under
a slight bit of reverse tension, in order to keep the tape taut from the supply
reel to the capstan/pinch roller which contains, incidently, the stretch (no
pun intended :-) that is in contact with the tape head.

|I never thought this would be such a big thing... :-)

  Misinformation always proves to be a major discussion point....

Randy Davis					UUCP: rjd@ninja.dell.com

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