Jacques Gagnon Adds RGB to a CRT TV for High-Quality Retro Gaming

By tying a DE-15 input to a TV's on-screen display circuit, Gagnon gets a "gorgeous picture" for any RGB-compatible vintage gaming hardware.

Gareth Halfacree
5 years ago • Retro Tech
High-quality RGB through an old CRT? Just abuse the on-screen display. (šŸ“·: Jacques Gagnon)

Vintage gaming enthusiast Jacques Gagnon has published a guide to modifying a classic cathode ray tube (CRT) TV into accepting a high-quality RGB video signal — by tapping into its on-screen display (OSD) circuit.

CRT displays have a number of disadvantages when compared to modern LCD-based equivalents, including their impressive weight. For vintage games, however, they're the only display type that offers the images in the way the developers had intended — taking advantage of how a single pixel is displayed on-screen to create impressive blending and even transparency effects which are completely lost when the same hardware is connected to a modern display.

Not all CRTs can accept an RGB input, however, which is where Gagnon's project comes in. "I did attempt doing this a long time ago actually on my first TV a Deawoo," Gagnon writes. "But I didn't do any OSD mixing circuit, nor lift the OSD pins, nor terminate RGB input etc. I had no idea what I was doing back then. So the picture was really really dark."

Working on a schematic originally developed for the Sanyo CP14SW1 by pseudonymous retro gamers Syntax and MarkOZLAD, Gagnon was able to add a DE-15 connector to a JVC TV in order to give it a high-quality RGB signal. The trick for the TV's missing native input: Tying the new input into the circuit used by the on-screen display (OSD).

"The result is gorgeous picture," Gagnon writes, "but the picture is a bit shift to the left. This can be fixed via the service menu of the TV. Alternatively an Extron sync processor (like RGB 203 Rxi) could be used to adjust the picture centering."

Gagnon's full write-up is available on the project page; the original mod design which inspired it is available on the Shmups Forum.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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