Better way to fix flickering PAL60 on early model DCs?

Just thought I'd put this out there -

My DC's a launch model console and has a few idiosyncracies - it refuses to load a couple of official titles (has done it since day 1) and often exhibits some slight horiztonal flickering in the top 10% or so of the image at the top of the screen when it runs at PAL60. This has also been a problem from day 1.

I figure the former could well be tweaked with messing around with the pot on the GD drive, so we'll ignore that. It's the latter I'm curious about.

The flickering doesn't kick in when the machine is running at 50hz or via RGB or VGA. It occurs when displayed via S-Video or composite video and only when the machine is in PAL60. I have found that by doing the R422 mod on the PCB it changes the colour channel to 3.56mhz (i.e. NTSC) and this gets rid of the flickering, but it also means I'm stuck using NTSC as the colour channel (I prefer PAL).

I remember reading a while back that others have noticed this issue (in addition to my DC, I've only ever personally noticed it on 2 other DCs over the years), but there was no solution. I'm assuming there's either an issue with the clock feed on my DC's video encoder or there's a problem with the encoder itself... but then again I might be going batty, as I don't know what the DC uses to generate the video output (my working knowledge of video encoders is restricted to the Mega Drive and Master System when doing different mods on them).

I don't think the issue is my TV - the behaviour has been consistent across every TV I've ever connected it to, and my current CRT workhorse deals nicely with everything I throw at it. This is the only anomaly.

Has anyone got any brainwaves on a solution? If not, then at least if someone else comes up with the same problem this post will note that switching the colour channel to NTSC is a reliable work-around for the problem!

 

Ahh thank you I had a dreamcast like this, it's nice to know there is a fix.

 

Glad the info has come in handy!

What would be even better is a fix if anyone has any ideas though!

 

i have a sega mega drive 2 with 50/60 hz switch. at 60 hz RGB it has the same behaviour you described on my samsung hdtv. top %10 of the screen is shaking. no problem at 50 hz rgb. couldn't try 60 hz composite yet but i can as now i have the composite cable too.

this behaviour disappears if i feed the 60 hz RGB to NTSC-U (60 hz) 32x and take the picture from 32x.

also this behaviour is not present if i use the same cable to get 60 hz RGB from my genesis 3.

this shaking problem is not seen on my sony crt, neither at 60 hz or 50 hz while using sega mega drive 2 or genesis 3.

 

Interesting... sounds like there are issues with your SMD's video encoder (or the state of the signals being fed into it), but that it's not too critical since the 32X's video encoder takes care of things... could be the sync maybe, or perhaps the oscillator input. Just shots in the dark.

What's interesting is that the problem on my DC is restricted to composite or s-video output - RGB seems fine, though I haven't tried SCART yet (only VGA). Might have to look into the DC's video encoder and see what's happening around there.