Dreamcast 4 wire mod chip install
Throughout the life of the Dreamcast there have been a number of different mod chips, the most recent being the 4 wire version, with only 4 wires to solder to quite large points it is relatively easy to install. Whoever you bought your chip from would normally provide instructions, just in case they don't though - read on...
Taking the DC apart is easy, the only tip mmmonkey can give you is to remember which kind of screw went where. Some people mix up the short/long silver coloured screws - the GD ROM drive is held on with 3 short screws, if you put a long one through here then you'll damage the motherboard. So be careful!
Here's a typical 4 wire mod chip, make a note of the colours, the chips that mmmonkey have used have always followed this colour coding - B Yellow, A Green, + Red, - Black, check yours and make a note of them. Check that the pre-soldered wires are secure, re solder them if they look or feel a bit dodgy. Don't forget to insulate the chip.
Once you've removed the power board and it's plastic shield, the GD ROM drive, the controller ports and the final metal shielding you'll finally reach the upper side of the motherboard which you need to solder the chip onto.
Here's an overview of the locations for soldering the wires, remember the colour coding (in this case B Yellow, A Green, + Red, - Black).
Lets start with wire A, this wire should be soldered to leg 28 of the 44 leg chip at location IC501, the BIOS chip I think.
Wire B is easier, look for the 3 legged chip at location D501, and solder as shown.
Finally it's just the Power wires to solder, very clearly marked at location CE502.
Now you need to replace the metal base/shield, if you've soldered your wires as shown above, then route them out of the gap near the GD ROM connector like this. This way they will not interfere with the metal shield or get squashed.
Place the GD ROM drive back on, and stick the mod chip down as shown, that's it - you're finished. You could partially re-assemble your console and test it, or just have some confidence and screw it back together and test it.
mmmonkey first bought a DC mod chip from lik-sang, these instructions are just new photos of the ones they supplied with the chip. If you are performing this on an NTSC console which you plan to use some PAL games then you may want to consider the PAL Colour mod as well.
If you perform this on a PAL console then you may find that some NTSC games will run at 50Hz with black borders. The only way to fix this is with either a boot disk (DC-X, Action Replay, Gameshark) for those games, by running the DC through a VGA box (most games will work in VGA mode, or can be forced to work) or by picking up an NTSC console and modding that instead. If you decide to get an NTSC console you can make life easier by fitting the PSU unit from a Dreamcast of your country to it, mmmonkey has placed UK PSU's into both American and Japanese Dreamcasts with no problems at all.
UPDATES
You could change the video mode and/or region of your Dreamcast.
You may buy a 4 wire modchip that is just a chip with no wires, not even mounted on a circuit board. Here's a couple of photos showing how to wire it up, I've kept the same colour coding as above to make it easier to follow. For the 2 +5v points, I linked them up using a leg cut from an resistor and then soldered the wire to that, you could just strip a bit more of the wire and solder it to both legs.
