[Coco] mpi upgrade

[Bruce W. Calkins]

Text excerpt from my files.
There is a JPG picture with the article.  I can send it upon request.

Bruce W.



Robin W Drake has converted the Radio Shack Multi-Pak 3124 satellite board 
upgrade for the CoCo 3 to a piggy back modification.This does require good 
soldering skills. You need a 74LS10 IC and Wire Wrap Wire. Both are 
available from Radio Shack. The Wire Wrap Wire is a standard stock item. The 
74LS10 is a special order. It is RSU10873495.
Soldering tip: Place a small amount of solder on the pin first before 
attaching any wire. Wire Wrap Wire is already tinned so just place the wire 
against the solder and lightly press against the wire with the soldering 
iron. As soon as the wire sinks into the solder remove the iron and hold the 
wire steady until the solder cools. As long as the solder wraps the wire you 
will have a good connection.

 Prepare the 74LS10 by bending all pins except 7 and 14 straight out from 
the IC body, then continue by bending pins 1, 2, 6, 9, and 10 straight up 
from the body of the IC. Then bend the skinny part of the leg on pin 1 
towards pin 14 until it is parallel with the top of the IC body. Now bend 
the skinny part of pin 2 towards pin 1 until it makes contact with pin 1. 
Bend pin 6 towards pin 9 until it's level. Bend pin 9 towards pin 6 until
it's flat with pin 6. Bend pin 10 flat and twisted towards pin 1. With pins 
11 and 12 bend the skinny part of the pins flat towards each other. Now 
apply solder to pins 1 and 2 also to pins 6 and 9 as well as 11 and 12. Now 
bare enough wire to connect from pin 1 to pin 10 and from pin 1 to pin 14. 
With pins 3, 4, 5, 8, and 13 bend the skinny part back and forth a few times 
till it breaks off. Now one of the tricky parts, your are going to bend pins 
7 and  14 of the LS10 so when mounted on top of IC3 "74LS367" in the CCMI, 
pin 7  of the LS10 connects to pin 8 of IC3 and pin 14 of the LS10 connects 
to pin 16  of IC3. Check fitting before soldering the LS10 squarely against 
IC3.

You will need to cut the trace from pin 52 of IC6 "TCC1001-1" to pin 19 of 
IC1"74LS246", cut the trace  just before it goes between pins 4 and 5 of 
IC1. Connect a wire from pin 52 of IC6 to pin13 of the LS10. Connect a wire 
from pin 19 of IC1 to pin 8 of the LS10. Connect a wire from pin 11 of IC4 
"74LS367" to pin 3 of the LS10. Connect a wire from pin 9 of IC4 to pin 4 of 
the LS10. Connect a wire from pin 3 of IC4 to pin 5 of the LS10.

The Multi-Pak is now CoCo 3 compatible.

Dave Deiter