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CoCo repack in PC

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Looking for CoCo help? If you are trying to do something with your old Color Computer, read this quick reference. Want to contribute to this wiki? Be sure to read this first. This CoCo wiki project was started on October 29, 2004. --OS-9 Al

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Home / Hardware - CoCo repack in PC

My CoCo3 (one of five, actually) in it's new home, a very large tower AT case. The case was wide enough (8� inches) to allow the MPI to be mounted inside the front cover. The fourth slot is not visible because the disk controller is mounted inside the case. For the cartridge doors, I sacrificed the case from a dead multipak and cut the entire door assembly out of it. It's held in the PC's front cover by some small screws and hot-melt glue (wonderful stuff).

The "sans CD-Rom" repack adapter includes my clone of the Tandy Hi-Res interface. I wanted it on the same circuit board as the other I/O connectors, for obvious reasons. There's a switch, barely visible between the two rightmost sockets, to choose between the left joystick socket and the Hi-Res socket.



CoCo repack adapter

In a CD / DVD, you can put the connectors for the coconut, in a PC

joystick, cassette, RS-232

CoCo repack Keyboard

My homemade keyboard... still not quite complete after several years. (I still need to make a top cover for it). Click for a closer view of the wiring. I forget what the keyboard came out of, but it's an old one with a good solid feel to it. It took me a little time to wire up but it was well worth it. It works great and I love it!

"CocoRepack" - How To Transfer A Coco Into an AT Style Case


ATCoCo - Putting it all in one Box By Mike Haaland - 72300,1433 Internet: Written: December 14, 1988 Updated: January 15, 1989

This article is the procedure I have used in order to get the clutter of Computer components off my desk and into a single AT Clone case. It has been put together and distributed to aid those CoCo owners who are tired of the mess, to do the same.

I cannot take responsibility for any damage you may do to your system while attempting the same project described in the text that follows. The need for such a transplant depends totally on your own tastes.

The nicest thing about the ATCoCo (CoCo in an IBM type AT case) is you have so much room for drives, packs, etc. that your system will be nice and neat without the need of having cables running all over the place.

Into the ATCoCo you have room for:

  • Three half-height disk drives
  • A full or half-height Hard Drive
  • The CoCo Motherboard (main circuit board)
  • An MPI (Multi-Pak Interface) RS Cat.# (26-3124)
  • Four Paks (fit in four slots of the MPI)

This is what I have installed into my ATCoCo! If I can figure out how to get the modem in there, I'll put it in there too!! My system has been running this way for over two months with no problems at all.


Before you can get started you will need:

1) An AT Clone case and power supply. (This case must be 6 inches tall inside. If you have an XT case you can still use the USING THE CLONE POWER SUPPLY section but the actual installation will differ, as there is not sufficient room in the XT Case to put the MPI (Multi-Pak Interface) on it's edge as described)

2) A set of all the connectors on the back of the coco, both male and female. ( Including the RGB connector if you are using an RGB monitor ). For the cleanest installation get the female chassis mount connectors.

3) Wire to make up the extender cables for the Cassette, Joystick, and serial ports.

4) A short ( 4 to 6 inch ) 40 pin extender cable that will go from the CoCo motherboard to the MPI. (Or you can make your own by using the 40 plug on the board and wiring a ribbon cable).

5) A VOM meter.

6) The ability to use a soldering iron.

7) GUTS! To void your warranty!!!!!!


I strongly suggest getting the IBM XT 101 keyboard adapter that Bob Puppo builds. Or get a Keyboard extender cable. Both can be found from various distributors in RAINBOW magazine. (If you ever received CoCo-Ads from PD Software there was an article in the Aug. '87 issue entitled "Detached Keyboard" that will describe how to make an external keyboard setup yourself.)


Make up the extender cables for the ports and check that they work properly. Each cable will need to be about 18 inches long.

Make the extender cable for the RGB plug.


This is a Copy of a message on CompuServe that I used as an example to hook my CoCo 3 up to an IBM Clone 200 watt power supply. It was written by Bruce Isted 76625,2237 and the MPI stuff was what I did.

COCO (Motherboard)

1) Remove Q1 (KTD880-main regulator power transistor) from the COCO 3.

2) Connect the external PS ground to pin 8 of IC8 (SC77527) or other ground point on the COCO 3.

3) Connect the external PS +12VDC to pin 16 of IC8 (SC77527) or to the cathode (positive) end of D1 or D2.

4) Connect the external PS -12VDC to pin 15 of IC8 (SC77527) or to the anode (negative) end of D3 or D4.

5) Connect the external PS +5VDC to where the emitter (output) of Q1 used to be. This is the pin on Q1 that connects directly to both R19 (51 Ohm, 1/4W) and R20 (0.1 Ohm, 1W).

6) Solder a jumper wire from the cathode (positive) end of D2 to the anode (negative) end of D14 to provide +12VDC to the input of the RF's +8VDC regulator. This was previously accomplished via an AC coupled capacitor (C62) and half wave rectifier (D13, D14), but there is no longer AC on the board.

By removing Q1, but still applying +/- 12VDC to IC8 (SC77527), you fool IC8 into thinking it is doing the +5VDC regulation, which does no harm as the voltage control (to the base of Q1) output has been disconnected. The internal -5VDC regulation is still done by IC8, which is necessary for cassette and serial (bit banger) I/O.

MPI (Multi-Pak Interface) RS Cat # (26-3124)

This is how I hooked a Multi-Pak Interface, ( cat # 26-3124 ) the newer small white model with the satellite board modification for the COCO 3, to the same 200W IBM Clone power supply.

To hookup a MPI (Multi-pak) to the same power supply.

1) Pull IC9 (1723CP), R7 (0.47, 2W), and C30 (1000P). (I cut out C30 so I could get to IC9 with a pair of wire cutters). Also remove the on/off switch.

2) Connect the external PS GROUND to any ground on the MPI.

3) Connect the external PS +12VDC to the solder pad in front of slot 1 in the MPI labeled 2. This pad is jumpered to all PIN 2's of the MPI slots. (Only needed if using an older disk controller that needs 12VDC)*

4) Connect the external PS -12VDC to the cathode (positive) end of D1 labeled "-12V TP3". This will supply -12VDC to all PIN 1's of the MPI slots. (Only needed if using an older disk controller that needs 12VDC)*

5) Connect the external PS +5VDC to the solder pad on the right of slot 1 of the MPI labeled "+5V TP1". This will supply +5V to all PIN 9's of the MPI.

  • This modification has worked for me for about 8 weeks so far with no problems at all. NOTE: If you don't have any peripherals that need 12VDC to power them you may skip steps 3 and 4. Some of the older disk controllers DO need the 12VDC from the MPI!!!


Remove you CoCo motherboard and MPI from their cases.

Lay your CoCo motherboard in the AT case with the ROMPAK slot facing away from the drives and the plugs facing the front of the AT case, as far back in the case as possible.

Mark where the four mounting holes on the coco are on the case.

Drill out the holes in the case.

You can either mount the coco with the plastic legs supplied with the case or build your own mounts using a small block of wood under each hole. Keep the CoCo off the bottom of the case ( about 1/8 to 1/4 inch ). This will give you enough room to run the DIN plug extension cables under the board and will also allow the AT fan cool the motherboard.

Put the MPI in the left hand front corner of the case with the slots pointing in and the card edge that connects to the coco towards the back. (Put electrical tape over the components that may be easily shorted to ground on the bottom edge of the MPI such as D1)

If you have a small extender ribbon connector for the 40 pin ROMPAK slot on the coco, you can see how easily you can connect the MPI to the CoCo. If you want to make up your own, you will have to:

De-Solder the card edge connector and remove it. Be careful, you will need it later!! Solder a ribbon cable to where the connector was. Solder the other end of the cable to the card edge connector. (Or use a small pre-drilled printed circuit board and mount the card edge connector to it and then run the ribbon to that). Be sure pin 1 goes to pin 1 etc.

The last thing you will need to do is use a piece of sheet metal to mount all those connector on. I cut out part of the PC card slots and made a plate to mount them. Plug everything together, and double check all the wiring. Mount the drives in their slots and hook them up to the power supply. Plug your various packs into the MPI. And you should be done.


Now that you have your ATCoCo all in the box and connected, here are a couple of "extras" that make you system more professional looking.

There are usually three lights, a momentary reset button, a two pole (on/off) 'Turbo' button, and a two pole key switch on the case. I have found some uses for some of them and here they are.

If you have a hard drive you can easily use one of the lights to indicate drive access by simply finding where the drive access light pins are on your HD and connecting them up. This is a big help if you have used the fourth slot (behind the front cover) to put your HD in.

You can wire one of the lights to indicate power on by hooking +5VDC from the power supply or and the other side to ground.

The 'Reset' switch can be wired up to where the original CoCo reset button is. Remember, you can't get to the original one now! Simply remove the old reset button from the CoCo and you can wire the new button to where the reset button was. If you can, get the male pins that will plug in to the connector from any electronics supply store and mount them to where the reset button was and plug the switch to that. This will make it easy to remove later if you need to work on you CoCo.

Now if you can, remove the plaque from you old CoCo 3 top cover, the one that says 'TANDY 128K COLOR COMPUTER 3' and mount that on the front of the new ATCoCo Case. (For the completed look!!)


This text file is how I did it and I assume no responsibility whatsoever for anyone following the procedure described above. If you mess up your CoCo, it's your own fault, not mine. By opening the original case on your CoCo or MPI you VOID your warranty. If I can be of any assistance to you, you are welcome to leave me mail here on the OS9 sig of Compuserve or on GEnie my mail address is HAALAND.

Copyright (c) 1988 by Mike Haaland - 72300,1433 Internet: