Reply To: Megadrive VA0 RGB bypass

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#23942
nzChris
Participant

Hi all, sorry to hijack but I’ve been trying to get my bypass board working for a week now with no luck. I’m no expert but have successfully modded my MD1 VA4 PAL with region and cpu overclock mods in the past. I have followed the guide to a tee, although there are some minor differences with my board.

– Cut all traces from the 315-5313 and left the pull up resistors.
– Removed the resistor on the csync and installed a 2.2k resistor as suggested.
– Cut legs 21/22/23 and 10 on the CXA1145, however during troubleshooting I ended up soldering directly from the bypass board outs to the DIN pins directly (and cut the traces by the connector for good measure).

I have used a multimeter and tested all signals to make sure they get to/form the bypass board and are isolated.

Various sources have said that you should install a 220uf cap and 470Ω resistor on the csync line in the SCART end of the cable, so I have tried this too.

My OSSC just says ‘NO SYNC’, anyone have suggestions as to what I could check?

I have just read this note on retro RGB and wondering if this could be the problem.
“I suggest soldering to the VDP’s sync pin, but not lifting it, as some model Genesis consoles require the pin for the Z80 to run.”