From: utzoo!decvax!harpo!eagle!mhtsa!alice!rabbit!wildman
Newsgroups: net.audio
Title: Re: Pinch rollers and biasing
Article-I.D.: rabbit.169
Posted: Wed Jan  7 16:46:07 1983
Received: Sat Jan  8 04:49:40 1983
References: rocheste.364


Mark was right-- I did leave one thing out of my last note.
The record-on/record-off transient also can cause quite
a bit of head magnitization if the head isn't coupled through a
transformer(the usual case).  The startup and shutdown of the
erase oscillator were not carefully considered until a few years ago
in consumer machines, much to some pro's distress.

The startup transient, whether from power on or record on, is still
the primary cause now-a-days.  While it IS somewhat machine dependant,
it takes place to some extent on all machines, even (and, in fact, due to
the dircuitry required for better performance , to a greater extent) the
best of the bunch. (Direct coupled head amps have to do something with
the bias current...)

All decks do do it though, at least to some extent.  I am not
aware of any that have a really bad time of it, but I deal
mostly with higher end decks (Lowest is something like Teac V7 or so,
a nice machine) and may not enounter it often.
I do demagnitize all of my decks regularly, with the power off,
and with a line-supplied demagnitizer with a *LONG* snout.
I also use iso-propyl on the heads, and freon TF on the rubber parts.
(Yes, by ALL means keep it out of bearings!)


P.S.  Mark--I didn't mean you-- Look around this newsgroup.