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Atari NTSC 7800 Video Mod Installation Guide
Disclaimer: This mod is designed to permanently remove the RF output. The mod will work if performed correctly to a fully functioning Atari. Perform at your own risk. I am not responsible for any damage done to your Atari.
Read this Awesome "Soldering is Easy – Comic" for Basic 101s of soldering here.
Tools You Will Need
Philips Screwdriver
Soldering Iron and Solder
Wire Cutters/Strippers
Needle Nose Pliers
Drill with 1/4″ and 3mm bits
Purchasing: This kit can be purchased from my store here
Turn the Atari over and remove the 5 screws. Set them aside for later. Remove the main board out of the console.
Using the need nose pliers, twist the tabs around the metal case so they are straight. Remove the metal casing (top and bottom) and throw it away (or recycle it) You can choose to keep and reinstall this later. It's not necessary and may get in the way of the amp kit wires.
You should now have the main board like this ready to modify. On the top left hand side of the board are the 5 parts you have to remove. They are highlighted in the picture with pink X marks. Use the wire cutters to cut both ends and dispose of these parts. Then you need to cut the 4 pins going into the RF modulator circuit board (silver box with circuit board attached to side).
The picture should look like below. These are where the input wires will connect to the amp kit to the mainboard.
Optional POKEY Audio:
Pokey Audio connects directly to the Red and White RCA Jacks. The mother outputs perfect audio and the amp kit is not needed for audio output.
Only a few games use the pokey audio, this step isn’t necessary unless you have commando, ball blazer, or some homebrew made game. If can choose not to install this wire. (Note: If the pokey audio is too low add a 6.8k resistor (or any resistor near that value) in series to the main audio out wire. This should balance out the audio better.)
RCA Install and Soldering:
Take the bottom half of the case and decide where where you want the RCA jacks to go. Some cases can be very brittle so be careful. There are 2 common locations for RCA jacks. It's a personal preference.
Use a ruler and marker and make 3 dots 15mm apart. Then drill 3mm pilot holes on the dots, and use the 1/4” drill bits on the holes to make them ready for the RCA jacks.
Attach the RCA jacks by mounting them into the case with the ground ring and nut on the inside. Make sure they are tight. Have the ground ring holes be at or near the top and bend them down to make soldering easier.
RCA Jack Wiring. Connect all RCA ground tabs to the ground output from Kit. Solder the yellow RCA jack to the Composite video out on from the amp kit. Red and White RCA jacks solder to the audio motherboard point(s) shown earlier.
Note the install shown below is only an example of final board placement and wire length. Looking back I could have made the wires much shorter and moved the kit closer to the RCA jacks.
Now you are ready to put the main board into the case. Peel off the bottom of the double sided tape and stick it to any clear and clean location. Make sure the amp leads and bottom and bare wires are not touching other metal parts on the motherboard.
Replace the top case and screws and you are ready to play your Atari with composite video!
I would recommend a change to the audio connection:
ReplyDeleteThere was a BIG improvement in image quality after I did this mod, however, I noticed that afterward, I was missing one channel of TIA sound. The most obvious example was the 7800 version of Xevious. The in-game music was missing. Also, some 2600 games had no sound or distorted sound. Midnight Mutants also had sound issues.
Then I came across the post from Tue Aug 23, 2016 3:52 PM from “River Patroller” at http://atariage.com/forums/topic/256230-av-modded-7800-missing-sounds-on-some-2600-games/
Once I found R5 (fortunately, I desoldered it instead of cutting it out) and re-installed it, I bridged R5 and R6 at the bottom and soldered the sound wire to the bridge, instead of the indicated hole toward the bottom of the board. Now, I have all audio channels, and Xevious and Midnight Mutants both sound as they should.
You can also connect the bottoms of R5 and R6 to different audio channels (one to left, one to right audio) for a “Fake stereo” effect. However if you add the pokey audio to this connection, you would have to choose either the left or right channel only for POKEY audio to retain the effect. I personally did not like it, because the sound separation just made things sound “off,” as the 7800 was designed around mono sound.
I am not certain if this applies to all 7800 versions, but it worked on mine.
Thank You! I came across this issue too and plan to update the article as soon as possible.
DeleteHi,
ReplyDeletefor the pokey audio, should i just solder one wire from where the purple arrow shows to both the red and white RCA jacks?
-Max
Yes
Delete