Task: Connect the Chroma Signal to the 5-Din Video Jack of an Atari 800XL for S-Video Output
Needed: Soldering Iron, Solder, Atari 800XL, Cutters, Wire
Time: 30-60 mins
Introduction
It remains a mystery to me why Atari did not connect both the chroma and luma signals to the 5-din video jack for S-video output from the Atari 800XL like they did with the 800. Instead, they combine the two signals into a single composite signal that can be connected to monitor along with a second cable for the sound. This makes connecting the 800XL to an HDMI monitor problematic because the video only displays in black and white. I have previously posted about the Ultimate Atari Video (UAV) modification that corrects this and provides nice S-video signals. However, there is an even easier and much cheaper mod that only involves soldering one wire to connect the chroma signal to the video output giving it S-video capability. I demonstrate this below along with two additional easy mods that improve the quality of the video.
Instructions
I learned about this mod from several posts on the Atari Age forums including this one and this one.
To start, let’s take a look at what the video signal looks like on a stock Atari 800XL with S-video converted to HDMI using a RetroTINK and displayed on an LED monitor. Notice that the signal is black and white and a bit fuzzy compared to the S-Video text shown by the RetroTINK in the upper left corner.
The first optional mod is to remove the C56 capacitor (shown below). This makes the image much sharper and is highly recommended. It does not affect anything else on the system. I used some small cutters to clip both legs. Note that not all 800XLs have a C56 so don’t be surprised if you can’t find it. You will simply see three resistors instead of the five components shown below.
The second optional mod is to remove the C54 capacitor or resistor. This reduces the vertical “jail” bars that can be seen on the right side of the image above. CAUTION: removing this one will eliminate the composite video leaving only black and white video when connected to a CRT monitor. To keep the composite, you will need to clip only right leg of the component and solder in a switch. Of course, you need to open the case to flip the switch unless you run it out of the case. Note that on one board I have C54 seemed to be a capacitor and on this one it seems to be a resistor.
Finally, the main required mod is to solder a wire from resistors R67 and R68 to the chroma pin of the 5-din video jack (see below). I used some high heat electrical tape to hold the wire in place. Note that R67 and R68 seem to be connected by a factory solder bridge. I placed the wire right between them with some fresh solder.
Below is the final result compared to the original image from above.
Comments
This is a pretty easy that mod that should not take more than an hour if you are handy with a soldering iron. The results are pretty striking and look even better in real life without the LED artifacts caused by my iPhone.
Here is the S-video cable I use to connect the Atari to the RetroTINK.
If you are curious, this 5-second video shows what the chroma signal from an Atari 800XL looks like on an Oscilloscope.