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JaF64 RF Modulator Replacement for 250466 SixtyClone board
I started this project not because it's unique, revolutionary or game changing for the Commodore 64, but because it's an interesting project to work on and I knew I would learn a lot.
Anybody who has built a SixtyClone Commodore 64 will know there is no RF Modulator. It is up to you to source one, either a salvaged original, or a modern replacement of which there are now several to choose from. For the experience, I wanted to design my own and using the original Commodore schematics as my starting point, I created the JaF64 RF Modulator replacement to output Composite and S-video on my SixtyClone 250466, dispensing with the unnecessary (for my requirements) RF circuitry. I'm delighted with the result.
Using simple through hole components, the JaF64 retains the 80's aesthetic and is very easy to build for anyone with a modicum of soldering experience. The JaF64 gets its power directly from the unregulated 9V at connector 1 of the M1 Modulator, using a L78L05ACZ-AP voltage regulator to convert to 5V. The JaF64 takes advantage of existing mounting holes in the 250466 SixtyClone to allow very secure mounting to the board resulting in a robust, flex-free design (see pictures).
The end result is, I believe, a simple and elegant solution with video quality output on par with anything I have seen short of an RGB Mod, or DVI equipped Kawari. Please see my notes about video quality below.
IMPORTANT COMPATIBILITY NOTES
The JaF64 has been designed exclusively for the 250466 variant of the SixtyClone. Whilst it is entirely possible the JaF64 will work on other variants of the Commodore 64 "longboard", this has never been tested.
The 250466 longboard for which it has been designed MUST have ground at connector 8 of the M1 Modulator. Test this with a multimeter to be certain.
The JaF64 will NOT work on the Commodore 64 "shortboard" (250469). This has a different connector configuration on the Modulator and is therefore not compatible. I have no interest in the 250469 and therefore there are no plans to make a compatible design.
This has only ever been tested in PAL. There is no reason the JaF64 will not operate as normal in an NTSC machine but please be aware his has never been tested.
I'm afraid I'm not in a position to provide any technical support.
VIDEO QUALITY NOTES
Without installing an RGB Mod, or DVI equipped Kawari, it is not currently possible to get an artefact free image from the 250466 SixtyClone. I certainly make no claims to this effect. These are my observations regarding video quality with my current setup which include: an LCD TV with HDMI and Composite Input; a cheap Composite and S-Video HDMI converter; a C64 to Composite cable, a C64 to S-Video cable and a 5 meter HDMI cable.
Composite - Direct to TV
This is not my normal method of connecting but the JaF64 does output a serviceable composite image, with the following observations:
- Picture is soft
- Faint jailbars visible with a slight magenta hue
- Some colour bleed visible in areas of high contrast
- Some ghosting in areas of high contrast
- Colours are accurate and nicely saturated
- Text is clear and legible despite obvious artefacts
- Some significant smearing with certain colour combinations.
Composite - Upscaled via HDMI Converter
My cheap HDMI converter doesn't handle the composite signal well and the result is awful, introducing very prominent horizontal lines and darkening the colours significantly. This method, for me, is unusable.
S-Video - Direct to TV
Untested. I have no suitably equipped TV with the necessary S-Video input.
S-Video - Upscaled via HDMI Converter
This is my normal connection method and the video quality here is really very good, with the following observations:
- Picture is very sharp
- Faint jailbars are visible with a slight magenta hue
- Minimal colour bleed
- Minimal ghosting
- Some smearing.
- Occasional checkerboard pattern
Please note: it is almost certain that with different equipment in your setup, your results will vary from that described here but to what degree I cannot say.
BUILDING NOTES
- Some of the solder pads are quite small and so a magnifier will be helpful
- Please refer to the BoM for component placement and value information
- The BoM provides suggestions for specific components which have been tested and are known to work
- For connecting to the 250466 SixtyClone, I suggest using standard 2.54mm pitch male/female connector pin headers easily obtained online. This will ensure the JaF64 can be easily removed if required.
- For mounting to the 250466 SixtyClone, I suggest M2 10mm hex standoffs which can be screwed/bolted securely in place
- Before soldering the connector pins to the JaF64, I suggest mounting the JaF64 to the SixtyClone first. This will ensure perfect alignment of board, connectors and standoffs and provide a stable surface to solder the connectors in place.
- I do NOT recommend installing the JaF64 in the SixtyClone without the additional support of the standoffs. This is liable to put undue strain on the connector pins.
JaF64 RF Modulator Replacement for 250466 SixtyClone board
*PCBWay community is a shared platform and we are not responsible for any design issues.
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