This is taken from the Digital Audio Concepts website -
"...I've been working on an adapter to connect a C128's 80 column video port directly to a video-game-to-VGA upscaler board such as the GBS-8200 or 8220 (i.e. ones sometimes called "JAMMA" boards). The C128 produces digital RGBIHV output pretty much identical to the old CGA video standard, while some of those upscaler devices require analog RGB signals (without a separate intensity signal), and composite H+V sync. This board seeks to address this mismatch.
My intent here is to reasonably duplicate the standard C128/CGA palette as described in the article on Wikipedia, including a suitable "brown fix" circuit.
At one end is the C128 video port connection. At the other end is a row of five holes to receive the wires from the scaler board's video-input pigtail, and two more holes next to them for power input. If you are using this adapter with a GBS-8200/8220, you can use its barrel connector to power it at 7.5 to 12VDC, and then use its two-wire power pigtail to send power from there to the RGBI-to-RGBA adapter.
The "Invert-Sync" jumper, located half-way back at one edge, is provided here to address an oddity with how the C128 interacts with the GBS-8200. If you need to use the GBS's "auto scan" button, you may first have to move the jumper to the "Invert" position, then press "auto", wait for the GBS to finish syncing, then move it back to the "Normal" setting. When the GBS finishes, you'll see a stable, but slightly jittery screen until you move the jumper back (at least, that's how my 8220 behaves)..."
PLEASE NOTE SOME SOLDERING REQUIRED! Wiring from PCB to video device, experienced soldering required
