Introducing the ARRGH EFF OFF - a brand new RF modulator replacement that improves the video output from the Commodore 64 and 128 to levels unmatched by anything else out there. Not only are jailbars, checkerboarding and noise significantly reduced, edges are enhanced without unwanted ringing.

Most RF replacements are based on the original Commodore RF modulator with some tweaks here and there (this includes my previous RF replacements). While these can improve the video output over the original RF modulator, this new replacement is built from the ground up and uses a custom and heavily refined circuit to deliver the best possible video quality.

Note the original Commodore 64 longboard (ASSY 326298) is not compatible but there are some simple mods that can also improve the video output of this revision.

Feature summary

• Vastly improved S-Video and composite output
• Direct S-Video output replaces the old RF output
• Direct audio output with optional support for dual SIDs, Lumacode or composite video
• Chroma attenuated to 300mV
• Adjustable luma:sync ratio (contrast control)
• Improved signals also available on the A/V DIN connector
• Fully assembled and ready to install
• Optional HDMI (DVI) output for the large VIC-II Kawari (longboard version only)
• Includes shielded wire and heatshrink for the optional luma bypass mod - see below for details

Install

Remove the original RF modulator, there are 4 tabs that need to be straightened and 4 grounding posts (longboard only) to be desoldered. You also need to desolder the 8 signal connections to the modulator - be very careful with these as they are easily damaged if not desoldered properly!

Insert the RF replacement into the mainboard (do not solder it in yet) and then the mainboard into the case. The rear ports should line up correctly in the case with no adjustment required. Once you have confirmed the alignment is correct, remove the mainbaord and proceed with soldering the ground posts and signal connections.

Setup

Right Channel Switch

Set the selector switch to the desired "right channel" output. A 3.5mm to 2x RCA cable or splitter is recommended

External: Left channel is SID audio, right channel will be whatever is connected to the "input" header. The most common use for this would be dual/stereo SID setups or LumaCode. For example if used with Lumacode, LUM from the VIC-II-dizer would connect to "input", and GND to "ground".

Dual Mono: Both left and right channels are SID audio.

Composite: Left channel is SID audio, right channel is composite video.

Remember audio signals can be safely spilt, but not video signals. You can for example use the 3.5mm jack for composite video on the right channel, and split the left channel audio into left and right (dual mono).

The board can also safely drive both composite and S-Video outputs at the same time but not dual S-Video or dual composite (using both the RF replacement output and A/V DIN connector). In most cases you shouldn't need to use the A/V DIN connector, but all the improved video and audio signals will be available there if required.

Note chroma from both the S-Video and A/V DIN connector is attenuated to 300mV - this conforms to the S-Video specification but will also work fine with Commodore monitors that use separate luma/chroma. If using [Sven Petersen's AV adaptor] (https://github.com/svenpetersen1965/C64-A-V-Adaptor) the "CHROMA HI" jumper should always be installed.

Contrast fine tune

Commodore used a fixed value resistor in their RF modulators which don't take into account variances in the video output of each and every VIC-II. I've added this option so the output can be tailored for your VIC-II and display combination.

To find the ideal value for your VIC-II and display combination, first set the potentiometer to the mid position and power on the C64. Change the text colour to yellow (CTRL+8), foreground colour to white (POKE 53281,1) and the border colour to light grey (POKE 53280,15)

Adjust the potentiometer to obtain the ideal contrast. Too low and the white foreground will appear light grey, too high will cause white to bloom and the yellow text will appear to shrink. This adjustment may also have an effect on jailbars if present in the light grey border, so it is recommended to play around until you find a sweet spot. Note this adjustment may have little to no effect depending on your display or upscaler - in which case it is recommended just to leave the trimpot at the mid position.

Longboard HDMI

This option will only work with the Large VIC-II Kawari that outputs a DVI signal over a micro HDMI connector. A micro HDMI port replaces the S-Video connector on the RF replacement and a flat flex cable (included) brings the HDMI from the Kawari to the rear of the 64 case. While this does remove the S-Video connector, both the S-Video and composite output on the A/V DIN will still carry the same improvements to video quality as the other versions.

It is highly recommended to confirm the HDMI output from the Kawari is compatible with your display before ordering as the Kawari does not output a standard resolution. Please also keep in mind this is a DVI signal, as such it does not carry audio, you will need to use either the 3.5mm jack or A/V DIN for audio.

Luma Bypass

This is an optional mod that re-routes the luma signal from the VIC-II to the RF replacement. While the RF replacement will greatly reduce jailbars on the 64 and 128, jailbars on the 128 in particular are very hard to remove due to noise picked up from traces running parallel to the luma signal. There are other factors that cause jailbars but most of this happens inside the VIC-II itself - nothing we can do about that, and things like lumafix may mask certain jailbars while increasing the visibility of others. Personally I wouldn't waste your time with lumafix but that's up to you ;-)

This mod requires cutting the luma trace at both the VIC-II end and the RF modulator end and substituting it with a piece of shielded wire (included) running directly from the VIC-II to the RF modulator. As this is more of an advanced mod it is assumed you have some idea what you are doing, and are willing to accept the risks (and a couple of cut traces).

First you will need to find the luma trace from the VIC-II and RF modulator. This will be coming from pin 15 on the C64 VIC-II or pin 17 on the C128 VIC-IIe and connected to the 2nd pin from the right on the RF replacement (when looking at the topside of the board). Be sure to do a continuity check between these points before cutting any traces.

Once you have confirmed continuity you will need to find the actual trace from the VIC-II. This is different for all boards and may be on the top side or under side, it could also run under the VIC-II socket so make sure you know which one it is before cutting. Take a deep breath and cut that trace. There, that wasn't so bad eh? Now do another continuity check to make sure the trace is cut, and that you've cut the right one. Now cut the RF modulator end. This will always be on the underside of the board - 2nd pin from the left when looking at the underside.

Strip around 1cm of the outer sheath from on end of the shielded wire and twist the wire into a point. Then strip 0.5cm of the inner wire and tin both.

For longboards Connect the inner signal wire to the RF modulator luma pin and the shield wire to the nearby post holding the RF modulator.

For Shortboards and C128 Connect the inner signal wire to the RF modulator luma pin and the shield to the pin next to it (3rd from the left when looking at the underside of the board).

Route the wire over to the VIC-II luma pin avoiding running it between IC pins or any component pins as these can easily pierce the outer sheath. Once you have a rough idea of how the cable will be routed, trim off any excess.

For the VIC-II end you only need to connect the inner signal wire. Strip the outer sheath but this time fold the wire back over the cable, use the heatshrink (included) to cover any exposed shield wire while leaving the inner wire sticking out. Strip the inner wire, tin, and solder to the luma pin for the VIC-II (pin 15 for C64, pin 17 for C128). Check continuity between the VIC-II and RF modulator and also make sure there are no shorts to ground before powering on.