K40 laser not homing

Hi everyone,
Please excuse me if I’m not doing this post correctly, but this is my first time on a forum.
I bought one of those cheap k40 lasers for myself at Christmas.
Until today I was using the supplied software with the dongle key.
Thinking that the problem was in the soft ware I installed Inkscape with scorch works.
But the problem still exists.
It seems to engrave fine but the question I would like to ask is, when first turned on and if the gantry was left in a position away from the home origin is it supposed the return to the top left home position.
Mine doesn’t it moves further down to the bottom left until it hits the left hand gantry rail resulting in a horrible grinding noise.
I have been in touch with the seller (china) who suggested one of the optical sensors was damaged.
i have replace both of these with ones of original spec and both metal blades are engaging, but now I am at a loss.
I would be grateful for any help I can get to resolve this, other wise its a return job.
Dave

With a multimeter, test whether the endstops are working. Check the wires all the way to the control board.

Here’s someone with a similar problem:

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The problem does sound like your end-stops not operating correctly.

I have replace both of these with ones of original spec and both metal blades are engaging, but now I am at a loss.

What did you use to replace them? I ask because I have never found a place to buy them. If you replaced just the optical sensor on the existing boards they may not work. These boards (at least the ones I have repaired) will not work with new sensors without changing the bias resistors. Not a good design…

My blog has lots of information on the wiring and repairing of these sensors. It is common for the sensor(s) to slam into the flag and get damaged. Then it works intermittently or stops altogether.

You need to ensure that both the x and y sensors are working properly.

On my blog, there is also a schematic for an end-stop tester if you want to build one.

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Or simply disconnected,
Or as seen in forum post here, a loose wire being in the way of optical switche.
Should be a easy fix, good luck.