Genesis 2 pin 107 examination

[ASSEMbler]

This thread is a work in progress. It's not so much about the mod as it is the
mechanics of the mod.

While researching this mod I took out a board and my trusty G10 and took some
clear pictures.

We know that shorting pin 107 to ground causes Japanese language mode.
However, what is connected to what is interesting as well.

http://www.assemblergames.com/images/genesis2/genesis%20008.JPG

The board.

http://www.assemblergames.com/images/genesis2/genesis%20009.JPG

Pin 107. Some guides ask people to lift the pin away from the board. This is unnecessary and overcomplicated. One can use a solder sucker to remove solder from the eyelet, then carefully drill out the connecting eyelet. Solder the switch to the now isolated top eyelet and somewhere on the large bottom trace which has many common points.

http://www.assemblergames.com/images/genesis2/genesis%20010.JPG

This is the bottom of the board, where pin 107 meets a common broad layer. The voltage is a bit of a question in my mind as so many components
use this trace. Roughly 5V
http://www.assemblergames.com/images/genesis2/genesis%20011a.JPG

Many components connect to the broad bottom trace.

http://www.assemblergames.com/images/genesis2/genesis%20012.JPG

This is only labeled 107 for the sake of continuity. The top is more interesting.

http://www.assemblergames.com/images/genesis2/genesis%20014.JPG

[madhatter256]

So what does this examination bring to light exactly? It is a bit interesting that a lot of components are along that trace, but I don't know....

[ASSEMbler]

Most people think the lack of 5V is what creates the language mod.
In reality, it's lack of ground.

[madhatter256]

A large trace area like that makes sense that 107 would be ground. I just didn't want to say anything since I'm no electrical engineer to know this stuff off hand, so I might have been wrong if I were to state that assumption from your pictures earlier.

[c_rpg]

Isn't the trace just VCC? The trace provides power to the ic's, the two capacitors are used to smoothen the 50/60Hz ripple out of the signal. The led lights up when power is on. Jap language would then be achieved by a digital low to pin 107, connecting it to a digital high would set it in English mode.

[TmEE]

I've been "drilling" the hole underneath the board and soldering a wire on top of it for quite a while... pin lifting is absolutely unnecessary and dangerous.

http://www.fileden.com/files/2008/4/21/1876835/MD2VA0MODS.jpg
http://www.fileden.com/files/2008/4/21/1876835/P7310017.jpg

sorry for huge pics, I don't know if here's resize tags...

[ASSEMbler]

That audio board gives me nightmares of carpet fires...

@C_rpg what do you think the threshold is?

Here's another refinement to the mod, all you need do is drill a small dimple over the bottom of 107 and isolate it.

The large trace on the top is big enough to tap into without worrying about starving something.

http://www.assemblergames.com/images/genesis2/genesis%20019.JPG

[c_rpg]

I guess 2,5V since it's CMOS. 3,7V would be ideal for a high level and on 1,3V you'd get a guaranteed low. The asic does work with 5V vcc doesn't it?

Isolating the pin works in this case but it is an unwritten law in electronics that you don't do that. An unconnected pin can sometimes lead to strange behavior of the device.

@TmEE: Clever of you to use hf shielding on the audio mod. I always hated how distorted the Genesis sounds.e

[undamned]

Haha, TmEE, I can never get enough of that franken-md of yours :icon_bigg I'm surprised it's still running with all those mods!
-ud

[drakon]

I lifted the pin (for the challenge). I got a spare genesis 2 for 15$ so I decided to give it a go. I was going to try to desolder that tiny thing. I pushed the two pins next to it as far away as possible. Then I foced the pin from behind away from the chip with an exacto knife and it just came off like that. Works fine. It was actually easier than I expected. How it connects to the components and how it works I'm really not sure. And how they discovered this trick again I'm not sure.