/vr/ - Retro Games

I have degaussed my CRTV.
It has noticeably improved the image quality. There are no longer coloured splotches in the corner.
However there remain two smaller dark splotches in two corners of the screen.
Even after multiple degaussings I have not been able to get rid of these.
Is it possible that I have damaged the shadow mask by improper degaussing?
Did I move the degausser to quickly or too close the screen?
How fast do you have to jerk the degausser to cause damage?
How close can you move the degausser before it causes damage?
What does the damage from too-fast, too-close degaussing look like?