So in the absence of new advice, I have gutted the machine. Boards out , removed all limit and interlock switches. I will replace those I feel are really needed. Will put in a new Estop , and home switches, so now looking at what is left of the spindle control circuit.

This is me following the ancient Northern principle
"Let the dog see the rabbit"

Click image for larger version.  Name: filleted.jpg  Views: 621  Size: 393.2 KB  ID: 28946

Am currently trying to identify the wiring I am left with, so give me time on that one!

I will be building a new panel, with stepper drivers and BOB, and am not expecting too much difficulty with making X and Z operate from the computer .

Bit of trepidation though about making the spindle operate and vary the speed, in coordination with the traverses .

All suggestions considered !