Denford Software & Machines

hi my dad has an orac training machine just recently an intermittant fault has been occuring on the z axis the computer loses its zero when it goes into negative the display will show for example -650 which is impossible as the bed does not have this much traverse i have downloaded countless circuit diagrams trying to find the driver boards for the x and z axis but i do not really know what i am looking for
i hope you can help
andy

When the machine looses position can you hear it stalling as it tries to move?
The problem may be mechanical or could be electrical. Does the machine move OK in the other axes directions?
A photo of the machine electronics would help us point you to the axes drives. (It may be possible to swap them over and see if the fault transfers.)

Intermittent problems that appear on older machines are usually down to:

Corossion / cracking of soldered PCB pads / connectors / relay contacts
Pins / connectors / terminals have worked loose
Wiring looms have worn through and are shorting to ground

Most people that have come on here with similar problems have found it to be something like corrosion - one person simply refitted a chip on a drive board, and that fixed his problem
You could get electrical contact cleaner spray and give the likely connectors and terminals a good clean and tighten