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New Build - Commodore 128 RGBI to RGBA Adapter For the JAMMA GBS-8200 & GBS-8220 Series

RGBI to RGBA Commodore 128 Adapter for JAMMA

We have taken the opportunity to restock the RGBI to RGBA Adapter for the 8200 series JAMMA boards. We have changed from 1/4 watt to 1/8 Watt resistors which make the build a lot nicer and the profile smaller.

Here is the info on the board -

"...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)..."

Updated 1st April 2021
Available from Stock £26.95 Plus postage, email


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