MD1 RGB, Jail Bars, Pin 6 and Sync

Hi Guys,

Just a short background on the console - I picked up a PAL Mega Drive 1 and Mega CD 1 and want to play in 60Hz RGB. have already modded the MD1 with the 3-way language and video single switch mod (EU 50, US 60, JP 60), there's an Everdrive-MD in the post for the Mega CD BIOS switching and US region ROMs, and I'm now trying to get the picture right. I had the blue jail bars in RGB mode.

http://assemblergames.com/l/threads/megadrive-1-cxa1645-mod.32194/page-13

So after reading this thread and a bunch of others about the issue, I opted to use a wire to ground out pin 6 on the CXA1145 rather than cut or lift the leg.

This proved to be an immediate fix for the jailbars. All colours are now solid and crisp, and the blues look great. Really chuffed with this result.

However... and perhaps even predictably, I now have what I think is a sync issue, as the screen is now shifted a good deal to the left on one of my TVs, and slightly to the right on another. This happens on 60hz mode only, which is weird. I'm 100% certain that the picture was dead center in both 50 and 60hz on both TVs before I grounded pin 6, because I was flipping back and forth to observe the speed difference on Sonic 1 with no picture shift at all. Now, I'm so close to a perfect 60hz picture here that I want to fix this.

My limited understanding at this point is that the normal RGB scart cable sends composite video signal to sync the RGB picture, and now that I've messed with the composite signal the sync is out, causing the shift. Although, it looks nothing like the picture where the issue is described here:

http://retrorgb.com/sync.html

Anyway on this same site it says the following:

"You can get csync by wiring a custom connector directly to the video chip, or by using a cable that gets sync from pin 1 (for the Genesis 1)"

I think I can open the cable and fix this myself. I just can't tell, from this info and looking at SCART pinouts, exactly which wire needs to go where. I also saw things about boosting the signal with capacitors and / or resistors, such as here:

http://mmmonkey.co.uk/console/sega/md-sync.htm

"The first thing I did was re-wire my RGB cable so that Scart Pin 20 was connected to Pin 7 on the Din 8 plug (C-Sync, NOT Composite Video)."

I'm cool with this part, but couldn't I just embed these components in the cable itself?

Can anyone tell me if I'm even on the right track with this and clear this last part up for me?

Thanks in advance

UPDATE:

I was ready to go ahead and mod my RGB cable, but couldn't find a 75ohm resistor (must have every other type of resistor to hand...).

So I went ahead and bought this cable in CSYNC configuration to see if it will help:

https://www.retrogamingcables.co.uk...a-genesis-1-stereo-rgb-av-scart-cable-tv-lead

As I think it's going to do basically the same thing as the mod would. Will post updates when it arrives.

UPDATE 2:

The more I'm reading about what this "colourburst" pin actually does, the more it makes sense that removing it could cause horizontal shifting.

I noticed a few people on the old thread complaining about picture shifting.

I think the reason more people haven't reported it is they're using NTSC TVs with NTSC consoles and thus "getting lucky" sync compatibility wise. Putting a PAL console into NTSC mode, on a PAL TV, without this oscillator, seems to be a problem combination.

I'm hoping this CSYNC cable is really all that's needed here, and I will be able to remove the grounding wire to pin 6, restoring full AV functionality, removing the jailbar interference, and having proper sync with no shifting

UPDATE 3: Since I made this post I purchased an XRGB Framemeister which, with the Csync cable, gives a perfect picture.