Why does my crt monitor go blank and make a clicking noise before coming back on when I change the resolution?

Question

When using Windows Media Center for example switching from full screen to minimized it always does this and I'm wondering why, and if it's harmful at all.
Otherwise the monitor works well, this just happens when I change resolution.

Answer 1

It is to do with the horizontal drive circuitry that moves the electron beam left to right and back in the CRT.


To produce a linear image on a flat screen the electron beam has to move faster at the edges of the screen compared to the center. This is usually done by a capacitor in the circuit called the S-correction cap.

The problem is that different horizontal frequencies (and so different resolutions or refresh rates) need different values of capacitor. The typical solution is to have a bank of small and large capacitors switched in and out of the circuit by relays.

What you are hearing is the clicking of the relay contacts as the monitor changes which capacitors it uses to create the correct S correction capacitor value.


Some monitors use solid state switches, and do not click. Some perform the S correction by other means, and do not click.

Answer 2

Guess they all do that. My CRT monitor does that as well and always has right out of the box.

Answer 3

All CRT's do that when changing resolution. It's just how they operate.

Note: It's not harmful.

Answer 4

for different resolutions monitors have different power needs...these sounds are made by the relays and the capacitors...there is nothing wrong with it...most of the monitors make this sound..