The cabinets had been cut for a cheap input block mounted
on a thin piece of press board.
This had to be changed.
So, I cut a block to fit out of 3/4" MDF. It was glued
into place flush.
To furthur support and seal, I cut a piece of 1/8" veneer, glued and tacked it on the inside.
The notch was cut to fit around one of the internal braces.
Here is the block before final seal.
The internal wirng was done with gold connectors and 12 gauge wire.