Well, major progress on the documentation front: I've managed to get manuals for most of the elements of the control as installed allbeit as installed in more standard configurations. Also got fairly detailed manuals for the main (18Kw) and opposing (11 Kw) spindle drives and the axis drives.
From this I've managed to work out in my mind which bits do what (it's an odd set up with bits of rom and ram dotted all over the place). The main CPU board as well as its 32 bit microprocessor has a dedicated subservient cpu dedicated to servicing the axis and spindle drives - and has shared ram through which they communicate. On board this cpu board is ram that holds the users CNC code. There is a ram card with battery back up that holds all the parameters specific to the machine tool. There are a pair of rom boards that give the controller its basic personality, and one of them takes an extra chunk of rom plugged into it that sets up the onboard PLC (Programmable Logic Controller) used to establish the 'ladder logic' for controlling the various functions such as tool turret rotation, parts catcher in or out etc. Masses of digital inputs and outputs on this controller.
I have a very strong suspicion that one (or both) of two cards in the control are faulty and at huge expense have sourced some in America that hopefully will be arriving in a few days time.
In the mean time while I'm waiting I'm doing a 'physiological tidy up' getting the wiring back into its correct trunking, sorting out loose wires and this evening actually giving it a 'wash & brush up' . I find it far more motivating working on a clean machine than poking around muck and grime.
What fabulous stuff Sugar Soap is. The cabinet paintwork was covered in years of baked on grime, but is cleaning up a treat with a bucket of warm sugar soapy water and a bit of elbow grease. Never used it previously on machines, just prior to painting and decorating - definitely stuff to keep in the workshop.