Hey all. After changing a monitors color depth to 24bit, the monitor freaked out and now it's stuck in permanent overscan with screwed geometry (noticably on the right side). Also changing the resolution to anything above 800x600 causes it to switch off. Recall button does nothing. I attached another monitor to the PC and it had no issue, so I'm guessing it's an issue with the monitor rather than the PC?
That sounds like something actually failed in the monitor and further use of it is possibly disasterous. I'm not quite sure what has failed but it is in line deflection area, and most likely some high voltage capacitor in there failed which can produce the geometry distortion observed.
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Tiido wrote on 2022-07-30, 13:22:That sounds like something actually failed in the monitor and further use of it is possibly disasterous. I'm not quite sure what has failed but it is in line deflection area, and most likely some high voltage capacitor in there failed which can produce the geometry distortion observed.
Figured as such. Thanks for the reply
GodModule wrote on 2022-07-30, 06:07:Hey all. After changing a monitors color depth to 24bit, the monitor freaked out
I am 100% with Tiido's diagnosis that the horizontal deflection circuit failed physically and you would need a TV/monitor technician to look into fixing it. The change to 24 bit might actually have caused that failure, as some early graphics cards were unable to run true color modes at the standard frequencies for that resolution. Contrary to popular belief, too low frequencies can blow up the analog circuit of a monitor easier than too high frequencies. A well-designed monitor would have its horizontal oscillator tuned in a way that it will loose sync and run at a random non-dangerous frequency before it blows up, but alas, not every monitor is well-designed. The problem with low frequencies is that during a scan-line, energy is accumulated that is momentarily released as high-energy pulse to push the beam from the right edge quickly to the left edge to prepare the next scan line. When the frequency is lower, energy is accumulated for a longer time, so more energy is accumulated. This could either result in the accumulator (technically: inductance in the line output transformer and the horizontal deflection coil) to not take any more energy (technically: saturate), and the extra energy causes a sudden increase of the current through the primary transistor that generates the scanning (the line output transistor). Another failure mode is that the energy accumulator can accumulate the extra energy, but when the energy gets released as a pulse for the horizontal retrace, the pulse is too strong and damages capacitors or again the line output transformer. In you case, it sounds like a fried capacitor in the horizontal deflection circuit.
A typical offender for low-scanrate truecolor modes are the Trident TVGA8900 cards (and possibly some modules of the TVGA9000 series) that could output 640x480 in true-color at something like 28 or 29 kHz, whereas VGA calls for 31.5kHz. There even is a remark in the manual that this mode requires a multi-sync monitor that is able to handle the low scan rate.
