Megadrive/Genisis switchless mods???

[Calpis]

5V/200 ohm = 25mA, which is at the upper limit of HC/HCT, but 'eh, it works.

[devzone]

5V/200 ohm = 25mA, which is at the upper limit of HC/HCT, but 'eh, it works.

actually its more like 15mA because you have to remove the forward voltage of the led from the calculation (which is around 2V)

3V/200R=15mA

[Calpis]

Not 0.7V of a typical silicon?

[devzone]

Not 0.7V of a typical silicon?

I wish they were

Years ago red leds had a forward voltage of 1.2V and green I think were 1.45V but now the red is around 2.0V and green around 2.2V, I guess we can blame modern (cheap) manufactoring techniques for this.

[ASSEMbler]

http://www.youtube.com/watch?v=Ma9Ho2T8g20

Throw one of these in as well. :-)

[Calpis]

That could be integrated (uh why?) without an audio amp and with the existing LED setup by using a current amp fed by clamped audio.

Something roughly like this:


The resistor value will need to be adjusted for the signal level and the cap value isn't critical at all. I don't think the input resistance is low enough to interfere with a TV load in parallel, but it could so connect right before output amp.

[devzone]

edit: I decided to remove this post in case members found it offensive

[andre31t]

Great mod Kudos to all involved in it's evolution

I really want to try it more for the ability to change region settings without ugly switches. i've got my u.k pal megadrive infront of me and I'm lost. Where do you connect the 7474 chip to 5v's is it one of the other jumpers? Also the region mod that i previously done involved cutting the tracer between jumper 2 and jumper 3, does this mod not require you to do so?

[cde]

I soldered the 5 volts to the cap on the motherboard (red wire)
and yes you will have to cut the tracks on the motherboard, you could use this for either the PAL/NTSC switch or JAP/ENG switch, depending on the jumpers you solder to

[andre31t]

Thanks CDE
is the cap on JP1?, The motherboard on my megadrive has the jumper near the megacd edge connector and it doesn't have a capacitator there. Does anyone know how to identify a source of 5 volts?

[devzone]

on the Z80 cpu pin 11 is +5v and pin 29 is 0v
with a multimeter check any of the electrolitic capacitors close by that show to be connected to these pins as a source of power

[cde]

No probs.:icon_bigg

I used this site for lots of useful info and good pics of motherboards, at the end he mentions the different position and layout of the jumpers on different revision megadrives.
You can see my version (with cap) and the other version with the jumpers moved and no cap.. But like Devzone says with a multimeter you can find a 5 volt source quiet easily.. i did and im amateur at best:lol:
http://www.mmmonkey.co.uk/console/sega/md1switches.htm

[andre31t]

Thanks guys when i'll give it a go

[andoba]

One question, if this is only connected to NTSC and PAL, it would switch only between those two, right? I mean, if I did mod a PAL MD, it would switch between USA and PAL, but JAP protected region games would still not work.

Am I right?

[cde]

Yes thats right, with this mod as it is you would have to choose either to switch between 50 and 60 htz, (pal or ntsc), OR Jap and English, as these two need seperate switches, and this mod can only do one. I am sure though that one of these guys on here who know there circuits and electronics far better that i would tell us another circuit that could control both switches with the one reset button.

[devzone]

The circuit mod(s) posted in this thread allows cycling through the following 4 modes

EUR-50
EUR-60
JAP-50
JAP-60

So japanese games are not a problem

[raylyd]

i have a mega drive 2 could someone help me would help me then i can do the same switchless mod for mega cd 2

[segaloco]

Man, this reminds me of a concept a friend of mine is working on. He is trying to make a global Sega CD Bios, one that bypasses the region check. Couple that with a switchless Mega Drive and you have yourself one sweet system. As for me, I prefer switch mods just because I love to have complete control over EVERYTHING. In fact, for Multi-Bios on Mega CD I am just going to make my own file, it is rather simple, just put three BIOS files together and buffer the file with 128kb and it works fine.

[l_oliveira]

The only problem I see with the SEGA/MEGA-CD bios multi region hack is how the hell the hacker will unpack the SUB-BIOS, hack it properly and then re-pack and put it back in the main CPU boot ROM.

It's really a much needed hack, by the way.

For the moment, to play foreign discs on my japanese MD-CD I make images of the disc, patch it's "IPL" with the security program of a japanese disc (which is smaller than the other two regions) and patch the difference with NOPs. The patched image is then burnt on high grade CD-R.

All games I tried this on worked flawlessly on my Mega-CD.

[ASSEMbler]

all that work to avoid reaching down and toggling a switch....