PAL 2600 'Vader' S-Video mod

[Macross_VF1]

Since this forum has been quite helpful and provided a good amount of assistance to me (and will probably continue to do so in the future) I figured it was time to give something back. Hopefully someone will be able to benefit from this.
 

Background
This actually started with an Atari 5200 that I added to my collection. I figured I should do something about the video signal as I live in Sweden and old NTSC RF-signals just isn't very good or easy to tune into when you live in PAL territories. I settled on doing an S-video mod on my 5200, this particular one in fact and got a good result. 

A few months later, I added a PAL Atari 2600 'Vader' to my collection and I started looking into video mods for it as well. I found another S-video mod, the instructions can be found right here on Atari Age. What really struck me was the similarity between the two. However the instructions were not quite clear enough for my taste, as they really didn't seem to take into account PAL consoles, only NTSC. So I figured why not make my own tutorial.  

Now while this is aimed at the PAL Vader I would be highly surprised if some/potentially all other four switch Atari 2600 versions/revisions can’t use alot of the information I’ve provided.

Why S-Video?
Partially because I have invested in a Retrotink 2X and it’s a great little device for this sort of stuff. The other reason is cost; an S-Video mod is far cheaper than a RGB mod, probably just a tenth of the cost and I have several Atari 2600 consoles. Plus I really like the kind of mods where I can pretty much put together everything on my own.

Schematic
I’ve cobbled together a schematic using photoshop and various resources found on the net. I have no idea where I got the base schematic so I fully admit to being a filthy, dirty thief (credit goes to whoever made the first one).  What I’ve hopefully done is make it easier to read and interpret.



Before attempting this you should really read up on the instructions I linked to above as it covers the essentials. There are a few differences however, for instance I haven’t used quite the same order for the inputs and outputs from the CD4050 chip. However that shouldn’t matter as the chip has several unused pins already and any of them should work. Also, a quick note on the 4050, many Atari consoles have this chip inside so you could potentially use the outputs from it instead; however my Vader did not so I had to buy a brand new one. It’s not a strictly necessary component but the picture quality is improved by its’ inclusion.

There are also references to resistors and capacitors in the original instructions, which are not particularly helpful, partially because the part numbers are hidden underneath the components on the circuit board and also the numbers seems to be different on PAL consoles.

Finally, my one personal contribution to this schematic is the circled 6.8k resistor for the chroma signal. I highly recommend replacing it with a 10k trim pot. Not only were it used to great effect in the very similar 5200 S-video mod, but as I discovered when I did this exact same mod on a light sixer, a 6.8k resistor made the colours really faded. My Vader on the other hand was fine with a 6.8k resistor but having the ability to make fine adjustments is a nice and potentially necessary bonus. Unfortunately I was out of 10k trim pots when I did this mod. *grumbles*



Installing the mod
Once the circuit has been assembled it’s time to crack open the console. Turn it upside down and remove the four screws. Take note that the screws comes in pairs and are ever so slightly different from each other. I don’t think it really matters but better safe than sorry. Flip the case over again and remove the top. It can be a bit fiddly due to the protruding switches but it shouldn’t be too difficult.


 

When the circuit board is free, the RF shield needs to be removed. There are several tabs around the shield that must be straightened out. I know there’s somewhat of an ongoing debate on what to do with RF shields. Some claim that it’s rather unnecessary in this day of digital devices and just throw it away. Others feel that the shield was put in for a reason and it should be left in place.

Personally, I like to keep my consoles as original as possible and besides, RF shields are sometimes truly integral to a consoles design, providing protection against interference as well as odd ball purposes like acting as heatsinks and providing Ground.



With the circuit board fully exposed, take note of the TIA chip in the middle, the marked point to the right and the trim pot to the left. The last one is important because the pot might have to be adjusted before everything is put back into place. Besides, it’s a common failure point, giving it a bit of TLC when the console is already open is not a bad idea.

I’ve also, provided a better close up of the smaller circle. This is the point where C212, C213 and R214 all connect and the place where I picked up the Chroma signal. I’m not completely sure it’s the best place but it certainly worked out well enough for me.





Now you could solder the wires directly to the top but personally I found it easier to flip the board and connect everything there. It also meant I could make a fairly small cut in the RF shield for the wires to pass through. I used some Velcro to fasten the mod circuit to the lower RF shield and a zip tie to keep the wires collected.





On the back of the console I drilled the appropriate holes and installed the necessary connectors. You don’t actually need two RCA connectors, it’s not like the system provides Stereo but it’s nice to have. I also installed a molex micro-fit wire to wire connector on the output wires, visible between the plastic case and the circuit board. It’s not at all necessary to do so but it will be really handy if I ever have to open up the case and do further service.



All that’s left now is decide what to do with the old RF cable and then put the top case back on. As stated earlier, I like to keep my consoles as close to original as possible and that includes the RF cable. However since it’s not needed and the plastic case have a lot of spare space I just left it disconnected inside the console.



And the result? Well take a look! The signal has been routed through my Retrotink 2X and then into the TV. Not bad for something cobbled together by a blithering idiot.



Closing words

I fully expect some of the smarter/more knowledgeable of you to point out all my mistakes and what I could have done better. Heck, I invite you to do so, especially if it turns out I’ve made any terrible and potentially dangerous mistakes with the S-video circuit. However, I really hope this will at least provide some help to someone out there. 

[Voxel]

I've just scanned through your mod, that's some effort you've gone to.  Great work!

[Macross_VF1]

Thanks mate! I have the necessary photos and material to do a similar tutorial for a PAL light sixer if it is of interest.

[Voxel]

21 hours ago, Macross_VF1 said:

Thanks mate! I have the necessary photos and material to do a similar tutorial for a PAL light sixer if it is of interest.

If you're happy to do it, then please share it.