Atari 7800 ProSystem User manual

Magic Knight S-Video Installation –A7800
This is a Basic Install guide –because this is a really easy mod to do! This guide will only focus on the install for NTSC
Atari 7800 systems.
NOTE: –This guide assumes you can use a soldering iron and understand the basics of where what needs to be
connected in regards to wires onto the AV out connections as that won’t be detailed here.
Tools Needed –
#2 Phillips screwdriver –For taking the 7800 case apart
Need nose pliers –to assist with bending the RF shield tabs
Soldering iron –cause that solder isn’t going to attach itself
Solder –cause the wire isn’t going to attach itself
Lengths of small gauge wire –different colors make it easier for each connection
A way to attach the mod board inside –I use 3M 10LB Velcro
RCA Jacks panel mount (1 min) –for your Audio Out
S-Video Jack panel mount –for S-Video output
Heatshrink tubing –for that slightly more professional look
Small cable ties –for even more professional look and to keep the wires together
Multimeter –to verify continuity of connections and check for shorts
Let’s Get Started –
1. Start by removing the top cover from the 7800 by removing the 5 screws along the bottom of the case. Two in
the rear section, three in the front. (Set top case aside)
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2. Remove the upper RF shield by using your needle nose pliers to twist the hold down metal tabs and make them
stand straight up and flat so they will fit through the slots they originally come up from.
3. Locate the area where wires will be attached on the resistor ladder section just to the right and below the RF
modulator area. The area circled in yellow is the resistor section for video taps.
4. Decide where you want to mount the MK AV board inside the system. A good place is on top of the RAM chips
above the BIOS rom. Avoid placing it on the 6502 CPU or Maria as they get hot.
5. Measure out the lengths of wire you will need for connections from the MK AV board to the resistor section and
also from the MK AV board to where you decide to place your AV out jacks. 14 total connections will be made to
the MK AV board.
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6. Solder your wires onto the MK AV board first to make it easier. Solder your wires that will go to the resistor
section along with your +5 and Gnd as marked on the MK AV board:
7. Solder your wires from the MK AV Video out section that will be connected to your AV out connections: (Chroma
& Luma are for S-Video, Audio L/R is designed dual mono not Stereo!)
8. Now solder the other ends of your +5 and Gnd wires from the MK AV board to the +5 and GND rails as labeled in
the upper center below: You can attach +5 and ground anywhere along these large traces on the board
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9. Solder the other ends of your resistor connection wires from the MK AV board to the following locations on the
South legs of the resistors shown below matching up the colors on this diagram to those on the MK AV board.
Trim your wires as needed for proper length.
10. Now prepare the 7800 case and drill the needed holes for your AV jack connections. Most panel mount jacks
require a ¼” hole for RCA and usually a ½” or 9/16” hole for S-Video. Be careful when drilling holes into plastic
of this age as it will crack easily. Start with smaller drill bits for pilot holes and work your way up. I use 1/8” bits
to make pilot holes and then work my way up from there. Placement of the AV jacks is a personal preference,
most will install them along the sides of the case and under the main board as that is where the most room is.
Here is an example of where I placed mine though this is more challenging due to tight spacing:
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11. Finish up by soldering all video out connections from the UAV to the appropriate AV jacks you installed earlier.
NOTE 1: The MK AV board does not have ground attachment points on it. So all ground connections to the AV
connectors will need to be made to any ground point on the 7800 main board. Again, the main GND rail in the
center provides several unused vias perfect for this.
NOTE 2: While the MK AV board does have audio filtering built in, both audio outputs on the board are tied
together for dual mono and are NOT stereo! So you only need to use one of the two output points. Additionally
you can use any of several other methods of filtering and modifying audio if you wish.
NOTE 3: Adjust the Luma brightness with the potentiometer on the board in small increments to dial in to your
preference.
Now you should be ready to enjoy your new s-video and audio connections that allow to connect to more modern
televisions for improved picture clarity and sound. Test everything before re-assembling your Atari 7800. Make sure
to double check all your connections for proper placement and verify you do not have any electrical shorts.
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