From my ShopBot PRT router, this was a back-up board if I ever needed it.
The drives Have been replaced and whatever they needed to do to bring it to new condition.
If you try to move a channel without a load on it, these typically will take out that channel...That's why I don't accept returns which very few electronics components are not returnable.
It's common knowledge within the ShopBot Community of this.
With that said, that's why it's necessary to keep a back-up board if you do any type of production with your PRT.
I also have a ShopBot Digitizing probe in another listing.