Laser trickling out

Here’s a ghetto hand-drawn diagram of the proper wiring for your machine.

Note that there shouldn’t be any continuity on the yellow wire as you noticed - It’s the LPSU +5v output. Neither it nor the LPSU +24V (black) are used on the laserboard so it is safe to leave them completely disconnected.

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Thanks! I went through and removed the black and yellow from the LaserBoard and LPSU. The pot is working great to show the 15mA but so far I can only get the laser to fire by pressing the test button on the LPSU.

Any ideas why the laser wouldn’t be firing when the command is sent from Lightburn to print? Is there something in LightBurn I should be troubleshooting? Some G-code tests I should run?

Better pic of the LaserBoard

At this point, other than the x/y axis, there are only the two wires going to ground and L+.

Thanks again for all your help on this one!

Very concerning about the soldering wires to the power connector pins. The green screw terminal has the same connections!

Disconnect the green and white wires from the screw terminal. When you touch them together, the laser should fire.

Leaving them disconnected, put a multimeter in continuity mode and touch - probe to - on board (white wire terminal location) and + probe to L on board (green wire terminal location).

Issue the command that causes the red LED to come on such as G1 X10 S0.8 F600

When the red LED turns on, I don’t get a full beep like if you touched the probes together, but you should see something on the meter readout…

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I thought that might get some cringes. It was in an attempt (although ignorant I’m sure) to ensure that there was a connection between the terminals and the pins. At one point I was unable to get continuity between one of the pins and its adjacent terminal.

When the green and white wires are pulled out, and then connected, the laser does fire.

With the wires still out, I put the multimeter in continuity mode and tested continuity across the two terminals that the wires were in, specifically (-) and (L). I ran the G1 X10 S0.8 F600 test several times and ran a print as well. Both times the red light flashed but there was no continuity (OL) on the multimeter. In addition to the tack of beep, there was no readout on the meter.

Can you take a clear picture of the entire back of the board?

In particular there is a 4 legged long black rectangle under this area with the terminal and power connector, we want to see if any legs are loose, if there is any burning or charring on the board, or any evident damage to the component.

You bet. I could only find one 4-legged component.

There does not seem to be any loose components or charring.

That 4-pin device in the box labeled L217 is an optocoupler. The pins on the top in that photo are its input, cathode on the left and anode on the right. The cathode is tied to the system ground plane and if i’m following these traces right, the anode is connected in series with R36 and the microcontroller pin (2.5).

Leave the board otherwise disconnected from anything but USB and +24V power. Hook your meter in voltage mode up to the screw terminals labeled, “Laser Diode Out” - these are the screw terminals just below the 4-terminal screw connector. Run a test cut from Lightburn and check to see if you get voltage on those terminals when the laser is supposed to fire. If so, good - we’ll move on to the next step.

With the meter still in voltage mode, connect one end to a system ground point (the upper-left pin of the optocoupler should work - if that’s too difficult to probe use the ground pin from the power connector or the shield from the USB connector), then run your test cut again with the other side of the meter connected to the following points and report back if the meter does not read voltage on any of them:
R36 left-side
R36 right-side
Optocoupler upper-right pin

These should all read roughly 3.3V if the “laser” is set to 100% power for your test cut.

I ran the following test:

That 4-pin device in the box labeled L217 is an optocoupler. The pins on the top in that photo are its input, cathode on the left and anode on the right. The cathode is tied to the system ground plane and if i’m following these traces right, the anode is connected in series with R36 and the microcontroller pin ( 2.5 ).

Leave the board otherwise disconnected from anything but USB and +24V power. Hook your meter in voltage mode up to the screw terminals labeled, “Laser Diode Out” - these are the screw terminals just below the 4-terminal screw connector. Run a test cut from Lightburn and check to see if you get voltage on those terminals when the laser is supposed to fire. If so, good - we’ll move on to the next step.

With the meter still in voltage mode, connect one end to a system ground point (the upper-left pin of the optocoupler should work - if that’s too difficult to probe use the ground pin from the power connector or the shield from the USB connector), then run your test cut again with the other side of the meter connected to the following points and report back if the meter does not read voltage on any of them:
R36 left-side
R36 right-side
Optocoupler upper-right pin

These should all read roughly 3.3V if the “laser” is set to 100% power for your test cut.

My results were as follows:

Laser Diode out - 24VDC
R36 left-side - 2.64 VDC
R36 right-side - 1.22 VDC
Optocoupler upper-right pin - 1.22VDC

I will note that the laser was set to 100% power

.

Looks to me like your laser fire pin either got really hot, hot enough to melt the solder or it might be just a bad solder joint. I would check with Ray and the gang to see if you would be voiding any warranty but if it were me I would re-solder that pin on the board. Looks like a cold or disrupted joint. Maybe take a closer look at it with an eye loop or a microscope if you happen to know someone who has access to one. I would check the other side of the board as well but I don’t know if there are any traces to that pin or not. If you are not sure of yourself with an iron, have someone experienced hit it. It needs to be hot and fast or you could damage the components in the nearby vicinity

At this point please don’t solder directly to any components on the board - we should wait for Ray’s official response when he gets back in the office.

Loather, is this a potential issue by R47? Just poking around the pics

No, the solder mask looks intact there. Plus, R47, R48, and Q3 are all part of the “alternate PWM out” driver and wouldn’t affect the “laser fire” path.

Thank you for all the help over the Holidays. Is there another diagnostic I should run to be able to get the board firing from the LightBurn software?

To give a brief update, everything appears to be functioning properly. The board appears to be fine at a glance. When the two wires (green and white) are removed from the terminal and connected, the laser does fire.

I used the multimeter to detect dc voltage on the board, I received the following results.

Laser Diode out - 24VDC
R36 left-side - 2.64 VDC
R36 right-side - 1.22 VDC
Optocoupler upper-right pin - 1.22VDC

I will note that the laser was set to 100% power.

Thank you for your help in getting this diagnosed.

Are there any other things that I need to do to get the board operational? Do I need a new board?

Thanks Ray.

I’m just back in the office today from the holiday break (mostly spent cleaning the house and rearranging the shipping room). Happy New Year!
Spent all day dealing with shipping, I think I’m about halfway done. Now to catch up on some support.

From your initial post, do I understand correctly that the C3D board worked properly at first (including firing the laser) and then this stopped working after the mA meter installation?

If so, I would say that something bad happened in the rewiring, and the opto was damaged during the power up incident, but protected the rest of the board. To which: the red fire status LED still turning on is a good thing.

Possible solutions include:

  • Hook up the L and Gnd wires up like so - there is a MOSFET to drive other things like a diode that should work. Note that this is hooking up to the actual ground plane of the board, so there is no longer protection afforded by the opto and any power spikes/ miswiring/ whatever caused the previous incident may now fry the board.

  • External opto module hooked up to the Alternate PWM Out header. Please have a look at this post: Board Not Firing Laser
    Hopefully you can find such a module on Amazon with quicker shipping.

  • Doing SMT soldering rework to replace the opto component on the board, if you are comfortable.

  • We can discuss another resolution if none of the above works for you.

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Brilliant, thank you! Happy New Year.

Will replace the opto, and check back in.

I purchased three of those optocouplers just in case. As soon as I installed it on the board it ran perfectly! Thank you @Cohesion3D, @loather, and @gement81 for the help. We are back in business.

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