Sega Master System II A/V mod + 50/60 Hz mod

Recently I bought a Sega Master System II from a retro game store. I bought it because I thought that it could be fun to do some soldering again, and to perform an A/V and 50/60 Hz mod. Without knowing it, the console that I received had already been modded, but since the mod work looked terrible, I decided to clean it up instead.

There was several problems with the mod. First, almost all the soldering points were "cold soldering" and had to be reworked. Next, there had been used a lot of hot glue, that I had to clean up. Then there was a defect switch that I had to replace, that required some case work. Last but not least, the mod itself missed some components to clean up the image quality on the composite signal.

I did not have the right component at the time of the modding, therefore I still need to open up the console some day and add a capacitor and a resister in series with the composite line. That's no big deal, and I will probably do it some day in the future. But for now I'm happy with the result of my cleanup work.

A couple of days later, I got a hold of another Sega Master system II. this time around, the unit had not previously been modded, which meant that I now had the opportunity to perform the mod from scratch. After cleaning the unit, I did the similar mod to the first Sega Master System II, that I had been worked on some days before.

This unit was another revision then the unit I cleaned up. It has the game Alex Kidd build in, instead of Sonic, and the RGB encoder chip, from where I tap the composite signal, is a different one. Minor changes, but in general the mod is performed in the same way.

This time around, I had found a useful capacitor that I added to the composite signal. This has a great impact on the image quality, compared to the other unit. I still need to add a resistor to fine tune the black/white balance. Here I'm considering using a variable resistor, that I don't have at the moment, and need to acquire first.

When it comes to the 50/60Hz switch on this unit, I decided to find some other connection points for the GND and +5V. I connected both of these to the transistor on the left side of the PCB.

I'm happy with the result, and it is nice to have the option to run the games in 60Hz!

Next up, I will probably buy the right component, to improve the image quality further, and remove the RF unit and instead install a DIN connector for some RGB video out. That should be a simple task, since the RGB Encoder offers all the connections needed for this signal.