Video Asylum

Posted by GrandpaBobby (A) on February 28, 2004 at 17:47:34

In Reply to: Re: Sony 36HS510 HDTV Wega...transient noise on power up...is it normal? posted by kjmarte on February 26, 2004 at 07:47:35:

The degaussing is actually a magnetic event rather than one having to do with static electricity. The metalic shadow mask (located just behind the face of the crt) is suseptible to magnetic fields. Any magnetism on the mask (perhaps caused by a vacuum cleaner, childs toy, moving the set in reference to magnetic north, etc.) can cause color inperfections. The fix to correct this is to demagnetize the mask each time the set is turned on.

A circuit allows a large inrush of ac power to a coil (resulting in the "boing" sound) located in proximity to the face plate. The current is then allowed to taper to zero. The action of this diminishing alternating field is to randomly orient the magnetic domains, thus destroying any static magentism. The actual sound is a function of the type of picture tube, its size, the construction of the degausing coils, etc. Every set has this feature -- some you can hear and some you can't.

Robert