CoCo 1 Rev F Installation

This page will describe how to install CoCoVGA in a Color Computer 1 with a rev F mainboard. Drilling the case to mount the button board is not necessary, but recommended.

Required Tools

For CoCoVGA main board

  • Phillips screwdriver to open the CoCo 1 case
  • Small flat screwdriver and/or DIP chip puller to remove 6847

For CoCoVGA button board

  • A template, either:
    • Printer and ruler to print template and check that it is full size and tape to temporarily attach to CoCo case -OR-
    • a PCB template, which may have been included in your kit
  • Drill and bits with diameters 3.5mm (~9/64 in), 4.4mm (~11/64 in), and in various steps up to 13mm (~1/2 in) and/or a round file, knife or razor blade
  • Small flat or Phillips screwdriver and pliers to attach button board to case using machine screws, standoffs, and nuts

For CoCoVGA audio connection

  • Drill and bit with diameter 6mm (~1/4 in)
  • A soldering iron and solder
  • Wire strippers, a knife, or razor blade to aid in removal of wire insulation

Parts in Kit

A CoCoVGA kit contains the following items:

  1. CoCoVGA main board
  2. CoCoVGA button board, including 2 machine screws with hex standoffs and nuts
  3. DIN-to-HD15 (VGA) cable
  4. Audio jack with red and white wires, if appropriate for your installation
  5. PCB drill template for button board (not shown), if available for your installation


Step 1 - Open the case

Disconnect the CoCo 1 from power and all peripherals.

Use a Phillips screwdriver to remove the 6 screws from the underside of the Color Computer 1 and set the screws aside for later.

Set the CoCo 1 back down on its base and remove the case top.

Step 2 - Remove/relocate 6847

Find the 6847 which should be located near the center case support post.

The system pictured has an RF shield mounted around the SAM and RAM. Leaving this in place requires the use of an extra socket to elevate the CoCoVGA board, such that it does not contact the RF shield. For information about how to optionally remove the shield such that CoCoVGA may be mounted lower in the case, see this page.

In this model Color Computer, the 6847 is installed in a socket. Use a small screwdriver to gently pry between the socket and the chip a small amount on one side, and then the other, alternating back and forth until the 6847 can be removed from the socket. Alternatively, use a DIP chip puller.

If your CoCoVGA main board already has a 6847 installed in it, then you will not need the one you just removed.

If your CoCoVGA main board does not have a 6847 installed in it, then ensure all of the 6847 pins are straight and gently insert it into the socket on the CoCoVGA main board. (See picture in next step to check correct orientation. Note the half-circle indentation on one end of the chip.)

Step 3 - Insert the CoCoVGA main board

Plug the CoCoVGA main board into the socket where you removed the 6847.

Step 4 - Install the CoCoVGA button board

Preparing to use a PCB template to install the button board

If an installation template was included in your kit, then tape it to the back of your CoCo 1 over the notch for the RF modulator (TV) output. Avoid mounting the template such that it will unnecessary to drill through the strengthening beams located inside the back of the case.

Start by drilling the two bolt holes (one on either side of the large hole) and then use the machine screws and nuts provided with the button board to mount it in place when drilling the remaining holes. (These steps are described in more detail, below. See "Drilling and installing".)

Peparing to use a paper template to install the button board

If you will be using a paper template, print it at 100%. Do not use "fit to page". Match your ruler against the printed rulers to make sure it is printed correctly. Otherwise, it may be necessary to ask your software to scale it up or down.

Cut out the template leaving some paper available to attach to the back of the top half of the CoCo's case.

Paying attention to obstacles inside the case (such as locations for screws), place the template in an appropriate location and attach it using tape. Over the RF modulator (TV) output is likely a good location. Avoid mounting the template such that it will unnecessary to drill through the strengthening beams located inside the back of the case.

Drilling and installing

The recommended diameters of the 5 holes are as follows:

  • DIN jack - 13mm (about 1/2 inch)
  • 2 machine screw holes (on either side of the DIN jack) - 3.5mm (9/64 inch)
  • 2 button holes - 4.4mm (11/64 inch)

The 4 smaller holes can be drilled using the appropriate sized bit.

It is strongly recommended that a smaller bit is used to drill a pilot hole for the larger DIN jack. (There is a high risk of tearing or cracking the case!) Then, progressively larger and larger drill bits may be used to finish drilling the hole to the appropriate size. Note that given how soft the CoCo case is, it is possible to run larger bits in reverse to make the hole and then a knife or blade can be used to cut the extruded collar away from the inside of the case.

If a 13mm or 1/2 inch drill bit is not available or won't fit in your drill's chuck, then once the hole for the DIN jack is large enough, a round file may be used.

Using a screwdriver and pliers, attach the button board to the case using the included machine screws, standoffs, and nuts.

Step 5 - Install the audio output jack

If appropriate for your installation (that is, your system does not already have an audio output by way of a composite interface), now is a good time to select a place on the back of the system to install the headphone jack. Ed Snider created a video of this installation procedure here. (Note that in this video, the leads on his audio jack are black and white, which differ from those which we are including with the kits. Also, in the video, he is connecting his leads inside a CoCo 2, whose attachment points differ from a CoCo 1. See below for more information regarding CoCo 1 rev F board installation.)

Strip a short section of insulation from the ends of the red and white wires and solder them to tap 3 of the RF modulator and ground, respectively, as shown in the photo below.

Find a convenient location to plug in headphones, amplified computer speakers, or other 1V peak-to-peak audio input device and make sure that the jack won't collide with the power supply, other existing jacks, or the cartridge port area. Drill this hole using a 6mm (about 1/4 inch) drill bit.

Mount the audio jack in the hole that was drilled in the back of the case using the included ring nut.

Step 6 - Connect the CoCoVGA button board

Connect the header connector from the ribbon cable to the CoCoVGA main board. The ribbon cable's connector is keyed and will only fit into the CoCoVGA main board header connector one way.

Step 7 - Close the case

Place the upper half of the CoCo case on the lower half, being careful to avoid pinching the ribbon cable between case halves. Be especially wary of the cable being caught between screw posts - it is possible to inadvertently put a screw through the ribbon cable.

Turn over the Color Computer and insert the 6 screws that were removed in step 1.

Once the case halves are screwed back together, turn the CoCo back over on its base.

Step 8 - Connect the DIN cable

Reattach peripherals and connect the DIN cable between the button board and a VGA monitor.

Related Sub-Pages