Hiya!!!
I modded a PAL megadrive1 with region+hz switches... on crt tv's it works perfect, but on my gaming 37" LCD TV (LG 37LH4000) the screen flashes and has problems under 60hz... I made a quick and dirty vid to show this:
VID 00017-20100702-1845.3GP (http://www.youtube.com/watch?v=JTPkJMdoJ9I#)
I have concluded it is the cable to blame because the same tv works fine with snes/sms/nes/ps2/ps1/everything at 60hz and has no probs whatsoever with on-the-fly switching... I did try turning on the console at 60hz, still same problems... (my ntsc cdx works also fine btw :) )
I took 2 pictures of the cable, maybe someone spots something wrong here?
(http://i48.tinypic.com/71h5de.jpg)
(http://i46.tinypic.com/2m82jwh.jpg)
Thanks for any input/help!
edit: I found out that after switching to 60hz and I press reset repeatedly several times the image gets stabilized, maybe I need to do some extra work on the md1? I followed mmmonkey's guide here: http://www.mmmonkey.co.uk/console/sega/md1switches.htm (http://www.mmmonkey.co.uk/console/sega/md1switches.htm)
Try adding the capacitors shown here. (http://members.optusnet.com.au/eviltim/gamescart/gamescart.htm#megamstr)
I did further testing with a higher quality cable too, still the same BUT I also tested on my 20" lcd/tv-monitor and it works perfect there! So it is a mismatch between the 37" tv and md1 output... I will try adding the caps and report back, thanks!