This jogged me memory about a pretty well known problem with early PC video control hardware that could, if programmed with really incorrect video timing, result in damage to the flyback power supply in monochrome monitors.
Here's a link to a more detailed exchange on the subject of monochrome monitor damage from software: How did this program burn out two monitors?
This post states:
This is an old known bug. You can burn out the IBM monochrome monitor by stopping the horizontal sweep while keeping everything else
running, and the Hercules card gives you enough control to do this
under software control. The video chip lets you select the horizontal
and vertical sweep rates independently, and zero rates are possible.
However, the horizontal sweep is used as the oscillator for a
switching power supply, as is typical in TV circuits, and with the
sweep rate at 0, DC flows through a coil with high inductance but low
resistance, producing an excessive current that burns out the coil.
Part of the problem is that the IBM monochrome monitor is a design lifted from an earlier, pre-PC product line, the IBM
Displaywriter, and in that product, there was no potential
vulnerability of this type.
and this post states
If you tinker with the registers in the 6845 CRT controller chip on
the video board, you can program in a horizontal scan rate that will
overheat the power supply in the monitor. The reason being that a
monochrome monitor is designed to only work within a very narrow
range of horizontal frequencies. The problem seems to come from
accidentally programming a 6845 on a herc display with values that
are appropriate for a CGA monitor. Such a mistake is pretty easy to
make whilst tinkering with graphics programming and accidentally
using the wrong setup from a library. Doing herc graphics with
Borland's BGI system seems to be pretty safe, as I still have my herc
Several people reported that a screen-saver program called "BURNOUT"
fried hercules boards, rather than the monitor. This surpirses me,
but several people were quite emphatic that it was the board that