Atari 2600 and Gemini composite video (A/V) mode with pause and ZX81 screensaver

[vcsrocks]

Hi all.  Happy new year!

 

For the past ten years or so, I have been fixing Atari consoles and often I install AV mods as part of the process.

 

At the beginning I was using a simple amplifier as many projects on the internet do, but I was not very happy with the video quality, so I quickly moved to the digital buffer approach.

 

As I convert a far number of consoles every year, from time to time I will run out of PCBs and, instead of just re-ordering the same design, I try to improve it and make it easier to install, better video and audio quality, etc...

 

Around 2018 I joined my AV design with my game pause mod:

 

Here are some examples of my previous mods:

 

 

The last PCB on the right is the one I used until mid last year.  There were a few things I liked about it:

• It had AV and pause integrated, so it was easier to install than two separate mods
• There was no need to modify the console case for the AV cable
• The pause was controlled by the COLOR switch, so no extra switch installation 
• The pause could be completely deactivated and the COLOR button could be used to switch the game to BW
• It could be mounted directly on top of the TIA and the labels on the pins made it easier to know which pins to connect for NTSC and PAL consoles.  The connections were made straight down which avoided making wrong connections

 

As it was time to order PCBs again, I started working on a new design to include some features I collected on my wish list:

• An easier way to configure the board for NTSC or PAL.  On the last board I made, a resistor network for this, which meant I needed to decide if I wanted it to be used for NTSC or PAL as I built the mod and it was not possible to change it afterwards
• Gemini support.  As the Gemini has a different TIA, I had to reroute the connections manually, which made the installation much more complicated and error prone
• An LED indicator for the pause state
• Better connections for the AV cable
• A better solution for the audio and video chaos while the game is paused.  The old board had addressed a lot of the problem, but that was a lot of room for improvement

 

 

 

So I came up with the design above which has a single jumper to configure PAL, NTSC and Genesis and the legends next to the pins show which TIA pins should be connected for each console type.

 

This makes it easier to install the mod and also change the console type after the board was build.

 

The other features are also included:

 

This is how it looks like installed in a Gemini:

 

So far I have converted a couple of dozens of PAL, NTSC and Gemini consoles with this new mod and I am quite happy with the result.

 

This time I ordered a larger number of PCBs though, so if anyone would like get one of these mods, I will soon put them on eBay for 29€, or you can pm me here.

 

Cheers.