Demag CD's really!?...
torstai 9. marraskuuta 2017 10.42.03 UTC+2 Brian Gaff kirjoitti:
I have a demag cassette from tdk this is simply an oscillator withe a small
button cell and a microswitch behind the coil that pusheds up to the head
when play is pressed. it is designed to tail off slowly.
Demagnetizers (proper name degaussers) for reel to reel machines
work in a similar way, but are more effective than their cassette
machine counterparts.
The principle is simple: an electric solenoid, or coil, powered
by alternating current, which produces a magnetic field the
strength of which alternately expands and contracts.
With the tape machine switched off, the degausser is gradually
moved into the close proximity of each head in turn
(but not touching it) and gradually pulled away after a few seconds.
All three heads are normally degaussed, (although the erase head
does not require it:-) It is important to degauss the tape lifter
path, and the capstan also.
I remember that one of our instructors used to wipe the end of
the degausser probe with a small piece of chamois leather,
which he then waived mysteriously in the air to allow the magnetism
to fall to the floor:-)) Strangely enough, most of the assistants
followed his example, and did the same thing.
This same instructor, a serious and rather quiet chap, had a wonderful
sense of humour. He once told an assistant in the lift, who was carrying
a box containing a 2" 24-track tape that the lift compartment,
made from sheet steel, lacked a Faraday cage, so he (the assistant)
should keep turning in an anti-clockwise direction all the time
the lift was in motion.
Some months after this, the technical director mentioned that he was
taking some visitors on a studio tour, and shared a lift with a
very courteous young fellow carry a multitrack tape, who kept turning in circles in front of them.
But back to degaussing, after which the tape heads, lift mechanism,
and capstan need to be cleaned with the proper fluid using a
cotton bud (or the same piece of chamois leather from which the
magnetism has been shaken:-)
Degaussing a CD would perhaps involve the same routine, but with a larger and higher quality of chamois leather, available separately from a specialist audio dealer at a very high price :-)
Iain
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