Apple IIgs RGB to VGA Conversion

How to convert an Apple IIgs RGB port to a VGA compatible monitor with minimal mess and absolutely zero modification of your Apple.

Parts List »

  • Gonbes GBS-8220 CGA/EGA/YUV to VGA Arcade HD-Converter PCB
    • Purchase it from wherever you feel comfortable: it’s going to take forever to get no matter where your source it. is a reliable source, but not the cheapest.
    • Be aware that this is a bare PCB – it has no pretty enclosure.
  • 5VDC, 2.5a Power Adapter
    • I pick up things like this from Digi-Key. I got part number T1058-P5P-ND. Get whatever you like, as long as it’s 2.5 amps or higher. The GBS-8220 board has a minimum rating of 2.0 amps, and is reported to not work well at this minimum.
  • Connector Ends
    • You’ll need one DB-15 Male with Solder Cups, one DB-15HD Male with Solder Cups and some project hoods. I got these parts from Winford Engineering, part numbers CNS15M, CNS15HDM, HOOD9, HOOD15. Be aware, though, they like to drop religious brochures in their boxes along with the product.
  • Ethernet Cable – any old length that will work for your project. Stranded wire will probably work best because it will wick the solder better and is more flexible so it will be easier “cable manage”, but I had solid so that’s what I used.

Tools List »

  • Soldering iron that will melt your particular solder.
  • Solder (I have some ancient stuff from the pre RoHS days that likely kills thousands of brain cells every time I use it. I don’t know what’s out there now but any standard electronics solder will be fine.)
  • Extra tools to hold the Ethernet Cable and plug in place while you work.
    • The classic “Helping Hands” could really help you here. I used a bench clamp to hold the plug and did the rest by hand.
  • Small “Jeweler’s” or “Precision” screwdrivers to assemble your plugs once done.
  • Wire Stripper capable of removing outer sheath from Ethernet cable, and for stripping 22-24 AWG inner wires.

Process »


  • If you’ve not soldered wires before, look it up on Youtube or Instructables before even attempting this. If you’re still not certain you can do it, ask around for help. Trust me, you don’t want to try and fail and have to re-order your jacks because you cross-soldered something or melted the housing.
  • Soldering irons are hot. Carelessness results in burns, fires, and possibly death. I cannot be held responsible for negative consequences incurred by you because you don’t realize that you’re trying to melt metal.
  • Follow the pinout image attached here. Match each color as noted with each number. Basically, you’re aiming to get each color signal from one end to the other, each color signal’s matching ground from one to the other, and the Composite Sync matched up. The rest of the lines can be ignored.
  • Ethernet cable works fairly well here, as it’s the proper diameter for the job and the color code matches up pretty closely making the job a bit easier. I used Orange for Red, Green for Green, Blue for Blue, and Brown for Sync.
  • AVOID pins 7 and 8 on the IIgs connector. These have live voltage and you don’t want to be making any short circuits. Carelessness results in shock, fires, and possibly death. I cannot be held responsible for negative consequences incurred by you because you don’t understand how electricity works.
  • “Tin your leads”. Apply solder to your stripped wire first, then to the cup. A tiny dab’ll do ya, get it all the way ’round the wire, just enough to change the color. If you have a “ball” of solder on there, it’s probably too much. Once applied to the wire, then place the wire into the proper cup and remelt the solder.

Optimal Settings for Clear Video »

Its no secret: the IIGS default output doesn’t line up with any VGA-like aspect ratio standard. That means that your default output is going to be blurry, have annoying vertical banding or both. The following are some tips on hardware and settings to obtain a picture that has the least amount of distracting artifacts.

  1. Use a monitor that has a native resolution that matches one of the GBS-8220 output resolutions. This will lead to less interpolation (i.e fuzziness) by the monitor hardware.
  2. In the GBS0-8220 settings menu, set the video settings thus:
    • Display
      • Set the resolution to the native resolution of your monitor.
    •  Picture
      • Sharpness: change to 03. This helps even out the fuzz on the pixels. That is, it makes them all equally blurry, so the display isn’t as distracting.
    • Geometry
      • H Size: change to 76. This removes most of the vertical banding issues you’ll see, most importantly on the GS/OS Desktop, but elsewhere too.
      • H Position: change to 29. This centers the display after the above change is made.

Note: When there is motion on the screen, graphics around the moving object(s) (i.e. the mouse cursor) will become a bit blurrier. This is an artifact of the way the GBS-8220 scales video and I have found it to not be correctable by any combination of scaler settings.

Optional Ideas »

  • Enclosures: Find a solution to enclose the GBS-8220, and mount it to the VESA mounting holes on back of your monitor. This makes the monitor+board a much cleaner and easier to manage solution.
    • 3D printing: Shapeways  – fully custom designed enclosure with M1.6 mount headers, M4 through holes on 100mm centers and all the ports in the right spots. You would need to pick up 8x M1.6 x 3MM screws for the board and lid, and four M4 screws that match your target monitor. I provide no guarantees this will work it because it’s freaking expensive and I didn’t print one.
    • You could use the ArcadeForge Scaler PCB Enclosure, but it’s somewhat expensive.
    • Or you could just use some generic thing that fits pretty closely and mod it with a rotary tool.
  • Pull the +5VDC current off the Apple IIgs motherboard and run the GBS-8220 off it. This way, when you turn the IIgs on, the PCB turns on simultaneously. This would likely require board modification or a “pass-through” adapter for your power supply connector. However, if your machine is already loaded with cards, you could give your power supply fits or cause the IIgs itself to become unstable.

Resources »

Video »