Many computer monitors will make a sound like a "thump" when first
powered on, when the degaussing system switches on. My HP mx70, for
example, has done this since it was new; many color TVs will make a
similar sound as well when the degausser switches on and before the
raster appears. As the last poster suggested, there is no way to
reduce or eliminate the noise, but it usually lasts only a second or so
as the degausser is not meant to run for any length of time. If you are
hearing the buzzing sound you report for any extended length of time,
the degaussing system is probably operating all the time, which will
actually remagnetize the CRT. (This is a rather common problem with
color TVs as well). The relay that switches the degausser out of
circuit may be sticking in its on state. If your CRT display has color
distortion (rainbows, etc.) after power on and after the raster
appears, I would check that relay. I would also try disconnecting the
degausser entirely. If the buzzing sound disappears, the problem is
somewhere in the degausser (relay, thermistor, etc). If your monitor
works well otherwise, the degausser is very likely the cause of the
loud buzz you are reporting. That your other Sony monitor makes a
similar noise (only not as loud) when degaussing also suggests to me
that perhaps something in the other monitor may be loose and vibrating
while the degausser is working.
Kind regards,
Jeff, WB8NHV
Fairport Harbor, Ohio USA
