That fixed it! I was being safe and had my soft limits .1" off the switch. Somehow yesterday I must have had soft limits off and it worked then I somewhere along the line turned 'em back on and it wouldn't work. I never connected the two. Senior moment!

Homing works great now.

Thanks, Hood! No wonder you have 6900 posts, you're the MAN! Saving us retired guys from ourselves over and over.

LOL, well its sorted now so we are both happy
Hood

Hey Hood,

Get this. After working for several days, now the Z goes to home, stops and doesn't go up off the switch, so I have a limit engaged message. It seems as if it's either not overriding the switch, or it isn't backing off the switch. The servo motor does NOT backup in Z like it does in X/Y. In X/Y it hits the switch and backs up a little, in Z, it hits the switch, the motor doesn't reverse even a tiny bit, and I get the limit on message and the LED's are on on the diagnostic page. What might that be? Granted, the knee is heavy but counterbalanced with 2 200 Lb. gas springs, so it moves pretty easily. I'm mystified again!

Sounds like noise, your switch is being seen  triggering momentarily then not again then againbeing seen etc, it will probably be too fast for the LED to be seen but Mach is picking it up. Try putting a value in the filtering for the home switches on the SS Config page.
Hood

I've put values in SS config for home switches from 0 to 1000, like 0, 2, 10, 100, 200, 300, 500, 1000, with no effect. Should I try something else?

no, its unlikely that it will help if you have gone that high
What kind of switches do you have? are they connected in series on all axis and going into one input or do you have seperate inputs for each axis?

Hood

Switch setup is CNC4PC C16. They are optical and are apparently connected in series. There is a wire going from the C16 X Home to CNC4PC C23 BOB Pin 11, another from Y Home to Pin 12, another from Z Home to Pin 13. Ports and Pins setup accordingly. This was working the other day just fine.

Only thing I can think of is to check carefully that there are no problems with the wiring to the BOB.
  I think I might be tempted to remove the wire from Pin 13 and fit a mechanical On- Off switch in its place with enough wire so it can be operated by hand from your control panel, then do a RefAll and operate the switch to see if it seems to work correctly, no need to wait until the axis is near the end of travel when doing that so its a relatively safe way to proceed. If all works with that then it has to be a problem with the optos or wiring, if it still screws up then it is from BOB in the way.

Hood

OK, I'll try that.

One thing I KNOW is there is a physical LED on the C16 and a physical LED on Pin 13 on the BOB, and both of those are ON when this happens, as well as the yellow LED's in Mach on the diagnostics page for M3 Limits and Home. So the signal from the opto switch is making it to the BOB at least far enough to trigger it's LED indicator and trigger Mach enough to show its LED's!! Seems to me Mach either isn't over riding the switches, or not backing Z off the switch, which is what I SEEM to be seeing, the handwheel on Z does NOT backup a bit like X and Y do when homing and I swear it used to back up! How can it come off the switch if it doesn't back up?

Sorry was busy working when I read your post earlier and mis-read thinking you had said the LED was not on, but reading your last post and going back I see you had said the opposite.
 Ok so it has to be some form of noise or bounce. What value do you have in the SS config for the home switch?
Hood