Hi Don, new jumpers came today so I was able to try this.
I was unable to get the laser to fire.
with the other end of the new jumper in L, I touched ground at 3 locations with the power & laser switch on:
I tested the new jumper for continuity and this was fine so I suspect it isn’t this?
Let me outline where we are with the troubleshooting:
The laser fires when:
The laser does NOT fire when:
Is the above all correct?
Do you have and do you know how to use a DVM?
When you run a job does the gantry move in x-y and its just the laser that is not fireing?
The above is all correct yes.
Yes I have a DVM & know how to use it.
Yes the gantry moves in x-y, for example i’ve been sending a star shape vector to the K40, and when I’ve chosen vector cut the head outlines the star perfectly just without the laser firing.
Ok, turn the laser switch to on,
With the DVM on DC volts document the voltage on each pin of the 6 pin and right hand 4 pin connectors relative to the ground pin.
Do not measure the left-most connector which is AC.
Then turn off all power and unplug the machine.
Then unplug the two right hand connectors on the LPS. A 6 pin and a 4 pin.
Measure continuity [ohms] between the L pin [far right-hand pin] on the 4pin connector.
and…
The 3rd pin from the left on the 6 pin connector.
You will note in the photo of the connector definitions I provided in an earlier post that these two pins are supposed to be connected internally.
We are verifying that they are.
Just tried this, the first pic is to confirm the DVM was going to the correct ground pin:
To reduce confusion let’s use this diagram, same a previous but this one has connectors and pins labeled.
For now ignore the left side…
Sorry a bit confused about your results:
In pict 3 are these measurement voltage (DC volts scale) or continuity (ohms scale).
Some pins (P2-P,IN, 5V, 24V & P1-24V, 5V) have no measurement??
I see that P2-L and P1-L are connected together that is correct and good. It suggests the problem is either with:
Also I just noticed in your panel picture the POT was at its minimal position.
Has it been in that position for these tests?
Hi Don, thanks for the diagram & quick response.
In pic 3 the measurements for p1 & p2 are DC voltage. Only the bottom measurement showing 0.00 is in ohms.
For the pins showing no measurement, the DVM reading went straight to “1”. This was the same for every DVM DC voltage setting (200m - 600v).
Understood, I’m glad we’re getting closer
The marker pen is just to show min and max power for the POT.
This does not make sense? These should be 0-5v levels for all but the 24V output? Usually when a meter shows 1 it is maxed out.
What are you using for ground? The ground on P1 or P2?
Can you measure a 1.5 volt battery with that meter?
Turn your POT to max and then see if the laser fires with the Laser Switch = ON and the Test Switch button.
Sorry, just realized I was using the ground on p3 & you said not to bother with as its AC. Should I use the ground on P1 or P2?
Yes:
Just turned the POT to max and noticed something strange, it doesn’t seem to fire at all at max, seems fine from 0%-50%, but then the strength of the laser seems to decline from 50%-100% where is doesn’t seem to fire (was making dots on some wood to judge this). I tried to attach a video but it was too large - the mA dial moving all the way from left to right at lower power from the POT, but moving less as I increase the power - seems things could be the wrong way round here?
To stay in sync. Reference these #'s in your answer please:
Something still wacky with the meter readings:
I looked at the manual for that meter and nothing seemed weird!
We need to get good readings on the battery with that meter before we can trust the next tests.
Next test if the answer to #1&2 are yes and we get the meter working right.
Put meter on DC volts and measure the potential at the IN pin (P2-2) relative to the ground pin (P2-3).
While turning the pot from extreme left to extreme right the voltage should change from 0-5V on IN. After we figure out how to measure with that meter we should do this?
With machine power off:
4. What is the resistance between the P3-FG and P2-G?
5. What is the resistance between ground on the controller and P2-G?
Meter readings
I suspected a scaling problem, as 2 other equivalent batteries read 13.98 & 14.21 … maybe the decimal point should go left 1.
Yes the voltage reads 1 across the battery on and on 2v scale, strange I know, when I push it up to through the scales the assortment of numbers stay similar while decimal point moves right, so maybe just weird scaling?
So what (with that weird meter) does the IN pin measure to ground when the pot is in the middle?
This is nuts:
Sorry for being redundant but I must have missed something
The laser fires when:
The laser does not fire when:
Tests show:
Pin P1-1 has 0 ohms when measured to P2-4.
When P1-1 is touched to ground the laser does not fire!
Ok… here is what makes your head hurt!
Since P1-1 is connected to P2-4
and;
the “Test switch” is connected to P2-4 [the controllers signal wire and the test switch are connected together]
and;
the Test switch" will fire the laser which means that P1-1 must go to ground when the Test Switch is pushed.
Yet;
connecting P1-1 to ground does not fire the laser
Usually when something is this wacky I start looking for ground problems.
Check this:
Is the ground in the LPS connected to the ground on the controller. (i.e. 0 ohms)?
Make sure you measure from a G pin on the LPS to a ground point on the actual controller PCB. Do not trust the PCB connectors.
No worries I appreciate your help!
All correct
Right, I get the logic. Strange how connecting P1-1 to ground doesn’t fire the laser when it does go to ground.
I measured from both P2-3 and P1-3 to what I think were ground points on the PCB … are these the small metal bumpy bits? My DVM showed 0 ohms. (see pic) 
Hard for me to tell if those are ground. The metal case for the USB connector and the metal rings under the mounting screws should be.
We need to go back and figure out why your meter is not working properly.
We must have some wrong assumption somewhere.
Understood, I measured for resistance touching the metal USB casing & it came back with 0 ohms
It is strange I’ll show you the readings for the battery as the scale increases:
Wow, that looks amazingly defective. It’s really disappointing when you so manifestly can’t trust the testing device. 
I hope that’s still under return or at least warranty.
Doesn’t look good 
I have a few pretty inexpensive ones and I am very happy with them.
While you are getting the meter thing settled lets try this test:
Laser Switch ON
With a jumper momentarily connect P2-4 to P2-3 and verify the laser fires
If it does then with the same jumper momentarily connect P2-3 to P1-1 verify it does NOT fire
Yeah it should really work, so I may have received a defective one by chance. Got a ‘better’ one arriving tomorrow.
Been quite busy today so coming back to this as much as I can!
By momentarily connecting the jumper between P2-4 to P2-3, do you mean holding both ends to touch both pins? Like in this pic?
Laser switch ON
