Hitachi CPT-1455 RGB mod

[vol.2]

Originally Posted by ostlar

That connector in the schematic is shown on the back of the CPT-1444, and it's a DIN-connector of some sort. It supports regular RGB input from a game console, and according to the schematic it's directly connected to the chip with just resistors in between, so I wonder why the chip is 4Vpp. It says Data RGB Output signal, so that specification might be for the output?

Now that I can see the socket on the rear, it looks more like that is a input for a microcomputer, probably at TTL level. However, it's worth checking to see if this will "just work" for RGB at PAL/NTSC (whatever the set does). It looks like there is a switch (which appears to be on the back of the set to the left of the DIN) that pops it between RGB and composite video, that would be my guess for the sync. It probably takes combined sync, and you would input that at Pin 4 on the DIN socket as per the schematic.




If you choose to do S-Video:

You might have to keep the luma on the composite input and just hack in the chroma signal to the jungle IC.

It also might be desirable to identify any comb filtering that is going on and bypass it if possible. Adrian Black just did a dive into s-video mods on a more recent set, but the principles should be the same (your circuit will just have less ICs and more discrete components). https://youtu.be/tCO0kl_RxrI?si=devQziMOXeikg5MS