Purchase and Install an Ultimate Atari Video (UAV) Board for Better Composite Video from an 800XL (1-3 hours)

Task: Purchase and Install an Ultimate Atari Video (UAV) Board for Better Composite Video from Your 800XL

Needed: Web browser, soldering iron, UAV board

Time: 1-3 hours


As I have previously reviewed, all of the Atari 8-bit computers have a monitor port that outputs a composite video signal. This is a single-channel analog video signal that is connected to a monitor or TV through a yellow connector that is often found as part of an RCA connector that also includes red and white audio connectors for stereo sound. The single channel of video is called composite because it creates a linear combination of the luminance (luma) that carries the brightness of the video along with the chrominance (chroma) that carries the color. The Atari 800 and XE models all have a composite signal generated with both luma and chroma signals. For whatever reason, Atari decided to not attach the chroma signal in the 800XL giving it an inferior signal for conversion to S-video and HDMI. It is much worse than what you get from an 800.

The Ultimate Atari Video (UAV) mod was developed by Bryan Edewaard to fix this problem. This is an awesome upgrade to the video of the 800XL and very popular among Atari hardware enthusiasts. I highly recommend it if you plan using your 800XL with a high-definition LCD or LED monitor. According to The Brewing Academy who sells the UAV, some important features include:

  1. An on-board regulator to create a clean video power source.
  2. A 3-channel video amplifier designed for 75 ohm loads.
  3. A pixel re-clocking circuit to remove skew and better align the 4 luminance signals into a perfect pixel edge.
  4. A carefully designed chroma-shaping circuit.
  5. An adjustable pot on the board which controls the phase between the chroma and luma signals. A nice side-effect of this that you can change the artifact colors. There’s also a jumper to invert the chroma which swaps the positions of the artifact colors.

The installation of the UAV is pretty straightforward with some basic soldering.


The first step is to purchase the UAV (currently revision D) from The Brewing Academy. There are are several version offered. I got the fully assembled board (i.e. the plug-in) version which is all ready to go for just $30. The kit comes with the assembled board, some wire, and a chip socket if you need it.

The second step is to identify the Atari 800XL you want to mod. Some 800XLs have chips in sockets making them really easy to remove. This is the one you want for this mod as it will save a bunch of time. The socketed 800XLs have a label on the bottom of the case that says they were made in Hong Kong. If you use a non-socketed 800XL you will need to de-solder the chip and replace it with the provided socket. This is doable but you will need a system for desoldering.

The third step is the preparation. You will need a soldering iron to connect five wires to the motherboard.

The fourth step is to open up the 800XL, remove the motherboard, and remove the RF shield. Remove the six screws from the bottom of the case and gently remove the top being careful to disconnect the keyboard ribbon from the motherboard. There are several screws holding the motherboard on the bottom part of the case. Remove these and then remove the motherboard from the case. This needs to be done at a bit of an angle due to the joystick ports on the side. Once the motherboard is out of the case you can remove the RF shield. On my 800XL, the top shield and the bottom shield were held together with screws (bottom) and tiny nuts (top). Some may have tabs you need to twist. You can discard the shield if you want. You only need it if you like listening to radio while you Atari.

The fifth step is to perform the UAV installation. Before you begin, I highly recommend this how-to video from Todd’s Nerd Cave. A great overview. Also read the instructions from The Brewing Academy. Here are the steps I completed. Refer to the labeled motherboard image below.

  1. Check the jumper pins on the UAV to make sure they are in the correct orientation. The figure below shows the jumper positions for each model. This can also be found in the instructions provided by The Brewing Academy.
  2. Remove 4050 hex buffer chip (see motherboard photo below). You will not this further. Install the provided socket if you need it.
  3. Connect five wires to the UAV. You will need to loosen the tiny screws on the green connector at the end of the UAV. A tiny metal loop will descend as you loosen. Lower it just far enough that you can insert one exposed end of the wire. Then tighten. Insert each wire as shown below. I used a black wire for the ground (position 1) and white for composite video (2), yellow for luma (3), red for chroma (4), and blue for color (5). Note that the ground slot between red and blue (fifth from right) is skipped.
  4. Solder the black and blue wires to the positions noted in the motherboard figure below.
  5. Gently push the UAV into the open socket.
  6. Solder the remaining three wires to the positions noted on the motherboard. Note that I had trouble getting the solder to stick to the chroma lead on the 5-pin DIN (red wire). It was heavily oxidized. Once I cleaned it off it worked fine. Some flux could be used here.
  7. Reassemble the motherboard and the case taking special care with the keyboard connector. The case can be a little difficult to reassemble because of how high the U1MB sits up. It is tight but should fit with some jiggling and tightening of the screws. Make sure the wires are clear of the cartridge slot.
  8. Test the mod by connecting the 800XL to an LCD or LED monitor. I recommend a composite to S-video connector to connect the Atari to an HDMI converter such as Retrotink. Here is a previous post about the S-video connector. Here is one on the Retrotink for HDMI conversion. You should get a clear and crisp video picture. A comparison of with and without the UAV is shown below using composite to S-video to Retrotink to HDMI.
800XL Motherboard with UAV Labels
800XL Motherboard with UAV Labels
Finished UAV Installation
Finished UAV Installation


This is one of the most popular mods for the XL series of computers. The results are well worth the time investment and the $30 for the UAV. Highly recommended. I did the mod on the same 800XL that I performed the Ultimate 1MB upgrade on. A powerful combination for the 800XL.

No UAV vs UAV Comparison with Jungle Hunt
No UAV vs UAV Comparison with Jungle Hunt