C64 RF Modulator Replacement
In the Commodore 64 the VIC-II (Video Interface Chip II) is in charge of generating the main video signals: sync/luminance (luma), and colour (chroma). Except for the first motherboard revision, all Commodore 64 have an 8-pin DIN connector through which these signals are accessible, but they are not equivalent to the Luminance (Y) and Chrominance (C) of the S-Video format. They are very similar signals but differ in amplitude, so they are not useful with modern video monitors/TVs.
The Commodore 64 has an RF modulator, which mixes these video signals (sync/luminance and chroma) to produce a Composite Video signal (with the same problems of lack of compatibility with modern devices) as well as an RF output (VHF) for older TVs.
The circuit shown here replaces the original RF modulator, occupying the same space, and offering the following advantages:
The luminance and chrominance signals are adjusted to make them compatible with the S-Video format by reinserting these signals back into the motherboard so that they are accessible via the original 8-pin DIN connector.
The openings in the C64 case previously occupied by the antenna connector and the frequency adjustment for channel 36, are now occupied by a Composite Video and Audio output connector respectively.
The data and files needed to make this project are shared in my GitHub repository: