Hey Reddit, help me figure out why old tube TV’s when they shut of have a shrinking dot in the centre that slowly fades out.
Thanks
In: Technology
Tube TVs work by shooting a beam of electrons forward, and when the hit the from of the screen they cause it to glow.
Normally the electrons are going to go straight, but by using electromagnets the beam can get steered across the screen drawing each pixel.
When you kill power the electronics still sort of work for a little bit as the power stored in capacitors inside drain, but as that happens the voltage it has to work with drops. With les max voltage it can’t generate enough magnetic field to steer the beam all the way left and right, or up and down.
As max voltage gets lower and lower eventually the whole thing shrinks into a dot before cutting out.
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