Mega Drive 2 - Switchless Mod
Righto, you've seen the excellent Switchless Saturn Mod, made possible thanks to Seb. I love it, it's fantastic so I wanted to use it to mod other consoles.
A big credit must go to Klaus at Woflsoft, this guide uses the chip pinouts that I read on his brilliant site, in fact, these photo's are virtually the same as Klaus photos, his guide was already perfect, my one is just here as a backup in case his site/blog goes offline.
This page assumes that you've got your 16F630 PIC programmed with Sebs code. Lets start my cutting the necessary traces on the motherboard (this is a PAL VA1 motherboard)
You can see from the photos above that I've cut a trace that leads to leg 46 of the nearby chip. This leg is used to select the Video mode - 5v for 60hz or GND for 50hz. I've also labelled the points I've used for 5v and GND which are nearby where you're working. You can also see I've scraped the green coating from the trace leading up to leg 46, then added some solder to it.
This time we're working with leg 107 of the same chip. This time, GND is for Japanese and 5v is for English.
And the last one to cut and prepare, this is to read and control the reset switch.
Here's the power (5v red, GND black) and video (blue) wires connected up to the PIC chip (stuck in place with double sided foam tape). When I solder the wire that controls the video mode, I have already added some solder to the scraped trace, I've also added some to the wire, then held the wire to the trace, and heated them up, the solder simply melts together and creates a strong join.
Exactly the same technique for the language (yellow) and reset (orange) wires. The white can connects to the pad near the reset switch, or you can connect it to the bottom left leg of the reset switch.
Now I've removed the power LED, and stuck the red/green LED in place (I usually test the LED with a coin battery first before sticking it down, to figure out which leg is red/green). I've used double sided foam tape. The middle leg of the LED is Ground. When I've done this switchless mod before, I used 2 x 220 ohm resistors, this time I decided to make it a bit tidier and use just one on the Ground leg of the LED.
The green and red wires connect to the relevant leg on my LED. I've bent the 220 ohm resistor so that it links the middle leg to a nearby ground point, because I'd already prepared one that the PIC connects to, I decided to use that.
How does the mod work?
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If you press the reset button quickly the console will reset like normal.
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If you hold it a bit longer, the power LED switches off, release it and the console switches video mode (the power LED flashes to indicate the video mode, quick flashes for 60hz, slow flashes for 50hz)
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Press and hold reset button, the power LED changes colour, release it when you want the desired region - Red = Japan, Orange = USA, Green = Euro
I usually leave my console in Japanese mode, and only change it if I have a cart that refuses to work in that mode.
Don't forget you'll need an RGB cable to get a colour picture when using 60hz video modes.
Summary of Components needed
1 x 16F630 PIC flashed with Sebs
code
1 x 100nF Ceramic Capacitor
1 x 220 Ohm Resistors
1 x 3mm Dual Colour LED with 3 legs
and of course - wire!
