| How can I get a fixed frequency (RGB) monitor to work on my PC? |
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| There are plenty of old RGB monitors (possibly from old Sun, SGI, or other workstations) around which are attached to outdated or non- functional machines. Most of these units are quality products by Sony, Hitachi or other vendors. You want an easy way to connect your VGA or better card to the monitor. It's may not be that easy, since many of these monitors are only capable of displayed non-standard pixel addressabilities, but read on.. The easiest solution (but not necessarily the cheapest) is a commercial solution. See the section from Declan Hughes, below. Most of the old RGB monitors are fixed frequency, meaning that they are intended to work at only specific horizontal and vertical scan rates. This is in contrast to many newer models which are variations on the multi-sync theme. Multi-sync means that the monitor can sync to a _range_ of scan rates, or a number of discrete scan rates, based on the incoming video signal. i.e. the monitor will detect the scan rates of the video signal, and switch to the closest scan rate it is capable of. Since a fixed frequency monitor can't do this, you have to make sure that the video signal your video card is generating is compatible with the monitor. To hook up a VGA card to a fixed frequency monitor requires three things: 1) A cable that connects the VGA output to the RGB (and possibly sync) on the monitor. This may be the easiest part. Fixed frequency monitors typically have BNC connections for video input, so you need a cable which connects to your computer video output (typically a 15 pin D-Sub VGA) at one end, and which has 3, 4, or 5 BNC's at the other end. The number of BNC's depends on how you plan to resolve the sync signal issue (see point 3). 2) The horizontal and vertical scan rates must be compatible. Some video cards have adjustable scan rates, and if you can adjust the video signal to be within the range that the monitor can handle, you might be in business. If you can't get the generated video signal scan rates to within the monitor's specs, you need a scan converter, which is a very expensive and complex device. Even if you can get your graphics controller to adjust to the monitor's unique frequencies, you will have to figure out what to do when you first boot your PC, and how to run DOS programs, if needed. Just about every PC boots up in the DOS character mode (720 by 400 pixels, 31.5 kHz Horizontal, 70 Hz Vertical). No fixed frequency monitor will operate at this mode. If you never need to use DOS, you may be able to set your autoexec.bat to start Windows immediately upon boot-up. 3) You must have a compatible electronic signal. The problem is this: VGA cards have separate channels for red, green, blue, vertical sync and horizontal sync. Most RGB monitors have 3 or 4 connectors, either red, green (with sync) and blue, or red, green, blue and a separate sync. The sync signals from the VGA card must be combined to be fed into the monitor. This is not as simple as soldering the horizontal, vertical sync and green wires together. Some folks have been able to get their monitors to work by building simple circuits. However, keep in mind that items 1 and 2 above _must_ also be satisfied. A company that provides the required video card is:
Software Integrators
51 Evergreen Dr
Suite A
Bozeman, MT 59715
tel: 1-800-547-2349
tel: 1-406-586-8866
fax: 1-406-586-9145
http://www.si87.com/
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