[Coco] Multi-Pak Modification to work with a CoCo 3 (model No. 26-3124)

[Bert & Peggy Schneider]

I've seen two different web pages with information on how to modify a
Multi-Pak to work with a CoCo 3.
 
What is the best way to make this modification?
 
I purchased both a multi-pak and a coco3 via E-Bay.  I'm good at
electronics, but I don't want to botch a perfectly good multi-pak if I
don't have to.
 
Bert Schneider
(Formerly OS9Bert back in the old CoCo days)