[G4] Speakers Interfering with Monitors

[Dave March]

As you've gathered from other replies by now, the
subwoofer's speaker magnet is throwing off the color
"purity" of your monitors.  Don't panic -- and don't
run out to buy a degaussing coil just yet.

Every standard CRT television or monitor has a
built-in degaussing coil, which powers up for a moment
when you turn the unit on.  These are usually powered
by a thermistor circuit, so they are most effective on
a cold start -- i.e., when all the internal components
have had time to cool down to room-temperature.  Now,
in the case of computer monitors, the circuitry
provides the option of activating the degaussing coil
when the unit is still warm, or even while in
operation.  When you restart your computer, for
example, the display reset cycle usually triggers the
degassing function as well (note: this usually doen't
happen if you're just waking the computer from sleep).

Also, as someone mentioned, most of the monitors still
alive today have the option to manually degauss, and
this is usually accessed from the monitor's on-screen
display, where you adjust brightness, contrast,
position, size, etc.  (you probably can't do this from
the computer's control panels -- use the buttons on
the front of the monitor itself).  If the monitor's
OSD doesn't have an option saying "degauss," then
maybe look for a "U"-shaped icon -- like a "horseshoe"
magnet.  If you can find it and activate it, you
should hear a click and a low hum, and the picture
should distort and jiggle for a second or two.  That's
what you want.

First, all the degaussing in the world won't help if
you don't deal with the cause, so you'll almost
certainly have to put that subwoofer somewhere else. 
Most computer speakers are "magnetically shielded,"
which just means that a non-ferrous metal cup has been
placed over the speaker's magnet to minimize the stray
magnetism around it.  It's surprising that Logitech
didn't put a shield on the subwoofer's magnet, but I
guess they were just counting on users putting it on
the floor, or somewhere other than next to a CRT
monitor (I doubt any flatscreen monitors would be
affected by speaker magnets).

So, move the subwoofer so that it's at least, say, two
feet away from both of your monitors.  That should be
enough.

Now, even after moving the subwoofer, there may still
be some residual magnetic "contamination" of the metal
parts inside your monitors.  The parts themselves may
have become magnetized, and thus will continue
"bending" the electron beam in unwanted directions
until the parts have been de-magnetized.

--Repeated use of the built-in degauss circuits should
be more than enough to clear this up.  But it may take
a while.  Give it at least 30 to 40 degauss cycles. 
(but don't do it all at once -- the degauss circuit
and coil draws a lot of current and generates heat, so
if you just keep hitting "degauss" over and over
without giving it time to cool down, you might fry the
circuit)

After that, if the color impurity still isn't getting
any better, THEN it may be necessary to go out and
find a handheld degaussing coil.  And if it doesn't
come with instructions ... ask me.

:-)



--- Ron Michaels <ronmichael at gmail.com> wrote:

> I just installed some new Logitech Z-2300 speakers.
> The sound is great 
> and I love them. The woofer is between my two
> 19-inch NEC monitors. 
> Suddenly my monitors have "screwed up" color.
> There's nothing in the 
> manual about this. Has this ever happened to you and
> if so, what do you 
> do about it. I can't imagine what would cause this
> interference from an 
> electrical standpoint, but I'm a relative novice. I
> have a G4, mirror 
> door, 1.25mhz with OS 10.3.9.
> Thanks for any help.
> Ron/Memphis
> 
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