[Coco] Problem w/MultiPak and Coco 3

[Bill]

I have a MultiPak that works great with one of my Coco 3's, and both of my
Coco 2's. 

However, my OTHER Coco 3 only shows me a blank, green screen when the MPI is
hooked up.

Anyone got an idea on this? I know that the soldered chips on the Coco 3
make it impossible(for me) to change out chips.

Thanks
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