Apple Colorsync 850 Monitor "phosphor burn" Questions

...down the video so you do not permanently burn that line you see into the phosphor coating of the CRT.At any rate, the vertical sweep circuits need repair before the unit will work again.Good

phosphor burn on it, chances are the red gun inside the picture tube is out. A sure-fire way requires an oscilloscope. Check the voltages on the three color guns at their corresponding pins on the CRT

...develop 'burn-in' and having them go inactive after a period on non-use made sense to avoid damaging the phosphor but LCD monitors don't suffer from that so the feature isn't as useful as it once