On 10.12.13 12:17, Vedran Vuk wrote:
No, no picture deformations whatsoever.

Mike,

I tried reducing the brightness level then did the same test, the problem doesn't occur then. Also, this monitor has a "Highlight" function where you can define either a portion of a screen or the whole screen and additionally bump the brightness in the defined area. But regardless, if the "highlight" is turned on, or just the standard brightness control is too high, it will dim to a certain level below its standard 100% after a short period. With reduced brightness setting this doesn't occur.

So, I'm guessing some circuit is at fault here rather than the tube. Now, I'm not a professional, but I do know the principle of a CRT and all the dangers that come with servicing it. So my question is, where do I start looking for the fault? I'm guessing something that feeds the flyback transformer might be giving out?

Check whether something overheats. See if cooling cures the
brightness change.