Video adapter for PAL Apple IIc

A friend asked me to see why a video circuit for the pal version apple IIc didn't work, I designed a new video adapter for him.

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The PAL version of Apple IIc has only monochrome composite output, this board provides color video outputs.

I used a cpld to decode the serial video output of the IIc. There are a few video modes and I used many of the signals from the 15-pin video connector for video mode detection, synchronization and decoding of the complicated way color is coded in apple IIc.

The adapter provides RGBS output that works in all the monitors/TVs that supports RGBS or have SCART input and also has a Composite video output that works with most monitors but some may initially have problem detecting the color signal, for this reason there is a variable capacitor to fine tune the color frequency on the adapter. It also works on the NTSC //c.

I am very pleased with the result and specially with how double high res mode looks in my crt monitor through composite out. It's true that IIc graphics was meant to be displayed using a crt monitor and composite video and there is where it looks the best

I used a XC9572 Xilinx cpld because it is easy to solder, 5V tolerant, cheap and available.

For composite video I used the AD724 ic. There is a jtag connector to program the cpld on board.

To build this project one needs a programmer for the xilinx cpld.

It takes power from the Aplle IIc so there is no need for external power supply.

I tested the last version of the pcb and everything works ok, I use PCBWay to make the pcbs.

My friend Akis Fletsios made a 3d printed case.

Hardware design and software released under the Creative Commons License BY-NC-SA


STL for 3d printed case

Standard Tesselated Geometry - 314.14 kB - 04/13/2022 at 19:46


ipf - 20.55 kB - 03/20/2022 at 22:15


jed - 69.99 kB - 03/20/2022 at 22:10


x-zip-compressed - 77.36 kB - 02/21/2022 at 19:06


plain - 5.78 kB - 02/20/2022 at 18:52


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  • 1
    Step 1
     The female RGBS pinout front view

    JP1   1+2 closed

    SJ1  2+3 closed

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