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
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