Big laser- two steps forward one step back

   The z-axis stepper driver is installed and works great. Now there’s a new problem. The laser did not stop at the z-limit switch. I checked the switch pins and it’s not closing. Replaced the connectors and still not closing. Now the real trouble. I shorted the signal pin to ground and the laser did not recognize that the origin switch was activated. I’m afraid that input is bad. Thoughts? I’m sort of at a loss.

More info.
The controller uses an optical isolator for the limit switches. The circuit is pulled high at 24 volts on the controller board and is looking for ground at the limit switch to complete the circuit. Two things are going on:
1. The z-axis switch is bad
2. Shorting the switch circuit at the controller did not activate the circuit.
I checked all the resistors, and checked the caps and diodes for shorts. All Spears good. There’s no evidence of a problem with the pull-up supply diode or with the optoisolator. I did not think to check the 24v supply at the limit switch connector, which is internally connected to the pull-up circuit. If that’s not showing 24v it’s a relatively easy fix to jumper from another circuit or replace the diode. If it is showing 24v I think it’s probably the isolator but I’m not at all sure.

Can anyone tell me where the old switch came from? I’ll order a new one.

Thanks Brett,
I'll try to verify the voltage tomorrow. I'm in the dark on previous part sources. I'll work on recording the sources for this round so it doesn't get lost.

This is what I documented in the wiki when I replaced the sensor in January last year. Lorin helped me get this working, also the coloring diagram was helpful.

Original auto z zeroing sensor (January 2017)

A replacement original sensor has been added back to the laser, this is a mechanical sensor. During the installation of the sensor it was learned that there is a partial failure in the laser's circuitry. To counteract the failure a pull-up resistor of 330K ohm is added in line between the 24v line and the output line.

That’s s good news! I should have checked the wiki. Can you tell me where the switch came from? It’s definitely failed but it sounds like there’s no reason to suspect secondary failures.

One other thing. The bad switch did lead to a minor head crash. This could have affected alignment. I’ll be in Friday or Saturday, but anybody in sooner could have a look