Well, I spent four hours cleaning solidified way oil out of the saddle internals to get at the 5 metering units for the Y axis ways & ball nut. The good news is that I have a relatively clean area to put things back together in, the bad news is that all five metering units are totally plugged up with gloppy crud. I expect the lines are also plugged up, but I can't get to the other ends without taking off the table. I expect that the metering units in the table are also plugged up, and they are impossible to get to without taking the table off and flipping it over.
Anyone ever take the table off one of these machines? Can the X axis ball nut be removed with the table in place, or does the X ballscrew come out with the table? It's not clear from the drawings in the books.
I checked the X and Y axis index pulses, they're working OK. I found a neat thing on the control, too: When the control is running, it displays the X/Y/Z position in the top left, like so:
The numbers are about what my machine reads before it's calibrated. When the control sees the index marker, it puts a decimal point after the axis that has the index active, in this case the X axis:
So, I confirmed that the control isn't seeing the Z axis index marker as the decimal point never shows up. I checked all the cables which are all good, of course. I started the reverse engineering process on the Z/S board, and have the index marker circuit pretty well figured out. Need to test it tomorrow. The Hurco boards are only two layers and are very easy to trace out, and use mainly regular 74 series logic which is easy to get. Much easier to trace the wiring than the Fanuc servo drive board, which is 4 layers with internal traces.