Separate Audio/Video Hack
by Sean Kelly


(The following is a modification which can be used to improve your ColecoVision. The authors of this list and this modification can not be responsible for any damage done to your unit or person as a result of attempting this modification.)

This is a rather feeble attempt at describing the hack to the ColecoVision video game system to give separate audio and video outputs to the system. I am what I call an "Electronics Tinkerer" meaning I have no formal education in electronics and basically only know what I have been able to figure out by ripping apart everything I own!

I am a collector of Classic video games and systems and ran across this hack on one of the many ColecoVision systems I own. It actually works quite well and gives the on-screen images a much crisper look to them. Audio is generally pretty poor on the ColecoVision and this hack doesn't do much to help it.

In order to get things started you have to open up the ColecoVision by removing the 8 screws on the bottom of the case. With the screws removed, the case is still something of a pain to open because of the lip on the expansion port, but just keep working at it and it will eventually come apart. Next thing is to remove the screws holding down the motherboard itself (three of them I believe) and take the motherboard out of the case.

On some versions of the ColecoVision the aluminum cover is soldered to the circuit board. If this is the case on yours, you will have to desolder it and remove both the top and bottom parts to the aluminum cover. Set everything but the motherboard aside and you are ready to get to work. The person that did the hack on this system uses a small automotive-type fuse block terminal to mount the components of the circuit board on. I have located it in the 1992 Radio Shack catalog (page 150) and it is RS part #274-688. It comes in a package of four for $1.29. Here is a list of the components used: AGAIN - I have no formal electronics education and don't really know how to read all the weird symbols on the parts. I will do my best to describe them (I have also labeled them on the line below for future reference - take note):

Transistor (T1) - No part # markings at all. Only thing on it is a white, red, and green stripe in that order from top to bottom. I assume this tells what kind/type it is? POSSIBLE (!) RS Part #276-1617 $1.98 (pkg. of 2)

Capacitor (C1) - Electrolytic type with part #N8408 on it. It also has the marking "470uf 35v", but the "u" is one of the funny symbols that I have no idea what it means. RS Part #272-1030 $ .99

Capacitor (C2) - Ceramic Disc type. Only marking on it is an underlined "47". RS Part #272-121 $ .39 (pkg. of 2)

Resistor (R1) - I know these are defined by the colored stripes (See - I'm not a complete idiot!! haha). The stripes are: Orange, Orange, Brown, and Gold.

A/V Cable - One Audio/Video cable with the RCA plugs cut off on one end.

You will also need about 5 small pieces of wire around 4" long each.

We're looking at a total of about five bucks to do this so for parts that do not come in packages of two or more, I would suggest buying an extra one, unless you know what you're doing, in case you screw something up. The center connector on your terminal will be the ground for all the components because it is the only terminal that sticks out on both sides of the block. The part the extends on the bottom will be used to mount to terminal to the ColecoVision motherboard. Directly to the right of the RF modulator (big silver box on the motherboard) right under the letter of the revision of the motherboard (the one I am looking at is "J") you will have to scrape off a section of the green coating so you can solder the terminal on the bottom to the motherboard. After soldering this bend the terminal block so that it is standing straight up from the motherboard.

Since many of the components will be "tied" together, you might want to connect them all to the posts first and then solder them later. The way I am going to describe how to connect them will (hopefully) make it as easy as possible to understand. The following is a listing of each post numbered from 1-5, left to right, looking at the terminal block from the back of the motherboard. Looking at the "back" you will be looking at the channel 3-4 switch as well as the RCA plug that is used to connect the ColecoVision to the TV/Game switch now.

Here is what goes on each post:

Post #1 - The LEFT "leg" of the transistor. I am looking at the transistor on the side that is curved - where you can see the color bands. One of the small pieces of wire goes from this post to the right leg of the disc capacitor on the ColecoVision motherboard itself marked "C22". Post #2 - The CENTER "leg" of the transistor. One "leg" from the Disc capacitor.

One of the small pieces of wire goes from this post to the underside of the ColecoVision motherboard. It will be EXTREMELY hard for me to explain where to connect this on the bottom of the motherboard since there are no markings on this side. The only way I can describe it is to say that it is being connected to one of the components in the RF modulator. The RF modulator is "outlined" in a sense on the bottom of the MB with solder because of grounding. You need to connect it to the pin that has the marking "+12" at about 5 O'Clock. This is the closest pin to he "+12" marking.

Post #3 - This is the GROUND post. One side of the resistor is connected here. The two ground wires from the RCA cables must be connected here also. Each Audio/Video wire has two wires inside of it. In general, one is shielded in plastic and the other is not. The unshielded wire is the ground. Connect the unshielded wire from each cable to this post.

Post #4 - The side of the Electrolytic capacitor (C1) that the arrow printed on the capacitor points to. This is where I am sort of unable to help you. The positive wire from the Audio or Video wire needs to be connected to this post. Since the RCA ends are cut off the cable I don't know which is which. It should not damage anything by connecting
them the wrong way, so you will have to take a guess. One of them goes on this post and the other goes on post #5.

Post #5 - The other of the positive Audio/Video wires gets connected here. One of the small pieces of wire goes here. This one is even harder to describe than the one on post 2. The "outline" in solder around where the RF modulator is mounted on the opposite side is where you are going to connect this wire. Looking at the bottom of the MB with the expansion port facing you the part of the "outline" you need to connect this wire to will be on your left. It's small section of solder (compared to the section on the right) and is about 1.5-2 inches long. Connect this wire anyplace here.

You now have one leg of the transistor (T1), one leg of the resistor (R1), and one leg of each capacitor just hanging there right? Connect all of these together, but do not connect them to any of the posts. Just sort of let them hang there.

The person who did this to my system also has one other wire connected to the bottom of the motherboard, but the other end of it has been cut and is not connected to anything. I assume this serves no purpose.

Copyright (c) 1994, 1995, 1996 Joseph M. Huber and James Carter

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