M2 Dual extruder. No power to both extruders

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b8smat
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Joined: Sun May 11, 2014 12:16 am

M2 Dual extruder. No power to both extruders

Post by b8smat » Sat Oct 03, 2020 7:40 pm

I had to repair the usb connector on my rambo board and after reassembling everything works except the extruders. Neither of them do anything.

XYZ motors and homing work fine
Bed heats up
Both extruders heat to temperature
Extruder fan and controller fan run
Bed fan runs with m106 command
All 3 fuses seem good
Led7 is on but led1 is not

But both extruder motors refuse to do anything. No movement, no noise. No warning about preventing cold extrusion.

Any suggestions?

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ednisley
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Re: M2 Dual extruder. No power to both extruders

Post by ednisley » Sun Oct 04, 2020 2:04 pm

b8smat wrote:
Sat Oct 03, 2020 7:40 pm
both extruder motors refuse to do anything
At the risk of sounding foolish, all the connectors are plugged in, right? [grin]

The nightmare scenario: plugging or unplugging a stepper motor with the power on can be a death sentence for the driver chip.

With the power off, swap the extruder motors with the XY motor, then try homing. The extruder motors won't run correctly, because the speeds / accelerations are all wrong, but if you hear / feel the extruders trying, then it's a likely a problem with the extruder drivers or the software behind them.

b8smat
Posts: 40
Joined: Sun May 11, 2014 12:16 am

Re: M2 Dual extruder. No power to both extruders

Post by b8smat » Mon Oct 05, 2020 1:23 pm

The extruder motor works when plugged into Z axis

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ednisley
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Re: M2 Dual extruder. No power to both extruders

Post by ednisley » Mon Oct 05, 2020 1:47 pm

b8smat wrote:
Mon Oct 05, 2020 1:23 pm
The extruder motor works when plugged into Z axis
Well, then, it's:
  • one of those mysterious firmware issues
  • a blown driver chip
If you ever, even once, connected or disconnected the stepper with the power on, then it's a blown driver.

If you had a single-extruder machine, you could tweak the firmware to use the other, previously unused, extruder driver, but that's off the table.

Although it's possible to replace the driver chip, it's difficult without the proper equipment and more practice than anyone really should have. The chip has a big fat thermal pad soldered to the board as a heatsink, so just unsoldering the pins around the edge won't release it and getting enough heat into the thermal pad is impractical.

b8smat
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Joined: Sun May 11, 2014 12:16 am

Re: M2 Dual extruder. No power to both extruders

Post by b8smat » Tue Oct 06, 2020 6:28 pm

I have dual extruder M2 and neither extruder motor runs. Do they run off the same chip? Seems unlikely that both blew at the same time. And I never unplugged them when they were on.

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ednisley
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Re: M2 Dual extruder. No power to both extruders

Post by ednisley » Wed Oct 07, 2020 12:35 pm

b8smat wrote:
Tue Oct 06, 2020 6:28 pm
Do they run off the same chip?
At least on the RAMBo V1.3, there are two driver chips.
Seems unlikely that both blew at the same time.
Stranger things have happened, but, at this point, I'd break out the oscilloscope to verify the chips are getting step pulses from the microcontroller. That bifurcates the investigation into hardware (blown drivers) and software / firmware (configuration, etc), but it's tough to probe a PCB from a distance.

Time to get in touch with MG's support folks …

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