Couple of CRT questions...

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Couple of CRT questions...

Postby Almoststew1990 » 2018-2-04 @ 19:17

I am using an IBM G54 CRT monitor that I got as part of a big bundle of stuff. I thought CRTs generally went up to 75Hz for a standard monitor. However, I've set the desktop to 1024*768 @85Hz. I've been playing Quake 3 at 640*480 and it seems to be outputting at 120Hz! Is this correct? How high do CRT refresh rates go? Is this comparable to a 120Hz LCD / LED monitor?

The monitor's GUI provides this information about the current mode:

What is the PP and NN mean? There isn't an option to scroll "up" to see a heading". I assume the 68.7Khz is the horizontal rate or something?

Finally, what is Degaussing for?

It's been about 18 years since I last used a CRT...
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Re: Couple of CRT questions...

Postby Deksor » 2018-2-04 @ 19:26

From what I saw, after the DOS days, there weren't really any standard for video refresh rates except that it usually won't go any lower than 60Hz. DOS mode 13h was running at 70Hz though.

120Hz on a CRT or 120Hz on an LCD is pretty much the same iirc, however 120Hz on a CRT make it to do much less eyestrain than a 60Hz CRT for example (and at 120Hz, my camera couldn't take the refresh rate artifact either which was neat as well ^^)
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Re: Couple of CRT questions...

Postby 133MHz » 2018-2-04 @ 20:11

Almoststew1990 wrote:How high do CRT refresh rates go?

Quite high depending on the monitor. There's no signal processing and phosphor persistence is very low. The limit is given by the deflection circuitry's ability to sweep the beam as fast as possible. As a general rule, lowering the display resolution allows you to attain higher refresh rates.

Almoststew1990 wrote:What is the PP and NN mean?

Sync polarities. One for the horizontal sync and the other for the vertical, P for positive and N for negative. Older monitors used sync polarity to determine which video mode it's being fed, but microprocessor controlled multisync monitors don't depend on it to work correctly.

Almoststew1990 wrote:I assume the 68.7Khz is the horizontal rate or something?


Almoststew1990 wrote:Finally, what is Degaussing for?

It applies a strong but decaying alternating magnetic field to the CRT to remove extraneous magnetism from the shadow mask (caused by the earth's magnetic field or other external influence) which causes discoloration. CRTs do a degauss cycle every time they're powered up, but since sometimes they're sensitive enough that just rotating the monitor on its swivel base can cause discoloration, manual degauss is offered as a button or a menu option to correct for this.
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