Granted I am sure this info is around on the net in different places, but I think most of it covers the multi-bios that has the 3 regions on one chip. If you are only interested in US/JP or UK/JP region swap however, then this will get you where you need to be as far as Model 1 and Model 2 systems go. Whatever bios you use it will need to be byte swapped before being burned off.
If you don't have an eprom programmer capable of doing 40 pin chips you will have to find someone out there who can flash said eproms for you. A member here did it for me, but I am not sure if he is ok with tossing his name out there for this stuff. But if he wants to chime in I can confirm that he is 100 percent reliable concerning the chip/eprom service.
Concerning the actual mod, some people prefer on the model 2 to take the pussy way out and slap a socket over the original bios and just slather hot glue all over the back side and hope it all holds connection. I did not do this, instead opting to strip down a 40 wire ide cable and do a 40 wire solder job leading from the original bios solder joints to the pins on a 40 pin socket. However you plan to do it is up to you.
http://i9.photobucket.com/albums/a66/Amakusa666/segacdregionmod_zpsf65645bf.pngAlso, as my understanding is people do this a lot by mistake. If you do this on a Model 2 on pin 20 of the original bios, rip it up off the pcb or destroy the solder contact from excessive burning on the pcb when trying to sever connection, don't lose hope. Just stop and take a breather.
Next take a close look around the bios. For sure on at least one revision of the pcb, on the top side of the pcb there is a trace that leads from said solder contact to under the bios on down to a via/through-hole nearby, so you can make a repair. It is possible they revised the placement or where this trace leads to on different revisions of the pcb, so just pull out that magnifying glass and led light and take a close look around.
As with most any trace repair due to similar damage where you don't actually need to repair/tin and relace the trace itself with copper/solder, you can take a couple of thin long threads out of a wire, twist them together tight and lace them completely with solder to make it hard, insert in the via on other end of trace that lead to damaged joint, and heat both ends. Then trim it down to make a new solid solder joint connection with the ability to solder on to it from either side of the pcb. After you solder your wire to this new joint, if you want to reinforce it you can cover the area with epoxy/enamel.
Topic: Sega/Mega CD bios mod (Read 506 times)
