CRT monitors are getting expensive. CGA and EGA monitors even more so. In theory, every 1980s computer that used those types of monitor had one at some point. But the survival rate of the monitors was much lower than the survival rate of the computers, so there aren’t enough of them to go around. That’s led to a need to convert CGA or EGA to VGA.
There are any number of ways to convert CGA to VGA, some of them more convoluted than others. The way I do it is fairly straightforward, but it does have some limitations, so you will have to decide if this is the right approach for you. The way I do it requires a simple converter, with the limitation being it only works with certain monitors because it strictly converts the digital signal to analog, so you end up with a 15 kilohertz signal that is technically closer to MCGA then to VGA.
But that 15 kilohertz limitation isn’t necessarily a showstopper. You may already have one of those monitors, or at least have one on your watch list because these are the same monitors that will work with an Amiga, Atari ST, Apple IIGS, and Tandy Color Computer 3. Examples include the Dell 2001FP and Dell E1912hf, but there are other 15 KHz monitors as well.
The adapter to convert CGA or EGA to VGA
GG Labs makes the adapter to convert CGA or EGA to VGA. It costs around $50. It is not a fully passive device. A built in microUSB jack provides 5 volts for power. I use an old charger from an Android tablet to power mine, and it’s working well.
As shipped, my adapter was almost ready to go. All of the dip switches need to be in the down position for CGA, Tandy / PC Jr graphics, and Commodore 128 RGBI. But I had to put jumper J4 into the position closest to the edge of the board to get my monitor to lock onto the signal.
For EGA, switches 1, 3, and 4 need to be up, with just switch 2 down.
For MDA, switches 1, 2, and 3 need to be up, with just switch 4 down.
Connecting to your CGA or EGA
The device ships with a DE9 plug on one side and a DE15 plug on the other. It’s really intended to sit between the monitor and the computer, with a straight through nine pin cable running from the computer to the device, and a VGA cable running from the device to the monitor. You can also remove the lugs from the nine pin side and replace them with 4-40 machine screws to hold the connector together, and then plug the nine pin side directly into the RGB port. This works well enough on a Commodore 128, Tandy 1000, or PC with CGA video built onto the motherboard, although I do recommend propping the board up to provide some strain relief.
Connecting to a modern(ish) VGA monitor
The way I’ve usually seen GGLabs’ CGA2RGBI adapter used is to connect them to a VGA to HDMI converter, since most of those devices can handle a 15 kilohertz signal, and then you can connect to any TV or monitor that has HDMI. This isn’t a bad solution, and it may be the best long-term solution, since HDMI is the most common video connector type now. But it does require a convoluted collection of adapters and cables to work, and both of the adapters require power.
So I prefer to use a slightly different approach that doesn’t require a second adapter. It means you need a very specific monitor, but that monitor will cost about the same as the adapter that you need, and possibly less if you are able to source a suitable monitor locally or happen to already have one. And then all you need is a plain VGA cable.
15 kilohertz VGA monitor
A small but reasonable number of flat panel monitors with VGA inputs have an undocumented ability to lock onto a 15 kilohertz signal. Many of them have caveats, but if the price is right, it’s usually little. And these are the types of monitors you have a reasonable chance of being able to find at a thrift store or estate sale. They don’t look like anything special, and in fact they weren’t intended to be anything special. Many of the monitors with this capability were the cheapest monitor in the product line when they were being made.
When I plugged my Tandy into the converter and then into my monitor, and turned them both on, I immediately saw a familiar 1980s display. The text was sharp and clear and the color reproduction looked like I remember it looking. It’s also about 40% larger than it would be on a vintage CRT, but my eyes aren’t getting any younger, so if anything, that’s a big plus.
So for $50, plus the cost of a phone charger and a suitable monitor if you don’t have those already, I like this option. It is much less expensive, easier to find, and more reliable than a vintage CGA CRT like an IBM 5153 or Commodore 1084, and I like the results. And EGA monitors are even tougher to find, so this is a fantastic option for an EGA display too.
The flat panel display is a bit anachronistic, but the results look good. This approach may not be for everyone, but I find it works well for me.