View Full Version : Strange mod to a Sega CD 2

02-18-2003, 05:19 PM
I've taken apart my fair share of Sega CD 2 and I happened to have one in pieces today to fix a sticky eject button when I noticed something I never saw in the last few Sega CD. Here's the picture I took: http://personalpages.tds.net/~wilykat/DSC01064.JPG

One chip is 7474 , and another is 7404 hex inverter. There are 5 wires total: red and black are obviously +5v and ground and the other 3 I haven't identified. Any idea what this board is for? A Mod chip? A bug fix? :? I could try and rip the board off and trace the circuit on the bottom (it's held by a double sided foam tape)

02-18-2003, 06:14 PM
Looks like a fix of some kind. The diagram appears to be nothing more than to delay and invert the signal. here's a quick diagram I made:

02-18-2003, 08:52 PM
I have another that looks just like that one. Must be a factory fix.

Nature Boy
02-19-2003, 09:54 AM
Was it a working unit or did you just take it apart to have a peek. I wonder if it's worth looking at my busted ones to look for the mod. Maybe it's not there and that might help me out.

02-19-2003, 11:01 AM
Mine was working when I took it apart, I had some trouble with the eject button. And I don't think this would help with your broken Sega CD, it appears to just shift the data half a clock and invert them. Possibly because of a chip revision required that at one point.