Fried all the stepper drivers :(

  • Guys I just decided to swap to a 24v PSU. So I unplugged everything from the maestro and hooked up the PSU. Soon as I switched it on all the stepper drivers fried.
    I’d checked the output from the PSU before trying it.
    Anyone know why this would happen? Is there a service to replace the drivers or is it a whole new board?

  • Drivers are just shy of $20 for 6 from digi-key but labor would probably set you back a fair bit, if you also have to add shipping it might start being cost prohibitive.

    Maybe you can ask a local cell phone repair shop to quote the labor to swap 6pcs 28-QNF chips (specifically 28-VFQFN Exposed Pad) or a local hacker space. All you need is hot air, some flux&solder paste + some practice. But as the cooling is done through the exposed pad its important to get the soldering right.

    When you say fried? Smoke? Think I've seen references to issues that would cause the communication to the drivers to fail, could be primarily the spi based chips, not sure - but please elaborate a little on the failure.

  • @SYCO said in Fried all the stepper drivers 😞:

    Anyone know why this would happen?

    Reverse polarity is the first suspect. Or the PS was really a lot more than 24V (more than 35, probably). Check it with a voltmeter before using it again.

  • Moderator

    @SYCO definitely sounds like reversed voltage, as number one here:

    Where are you? If in the UK, @dc42 may undertake the repair for you. Though he is very busy!


  • They fried smoke and flash and they all have small burnt dots on them.
    Kinda concerned about hooking another one up to the PSU.
    I am UK based. Used a 24v PSU from E3D and checked it was 24v before connecting it.
    Maybe I’ll buy another and then see about getting this one fixed.

  • If the wrong polarity is the prime suspect and you checked it; then its time to verify

    meter correctly read negative voltage
    leads are not swapped around
    supply is labeled correctly

    test the supply again, make sure to swap the leads around and check it shows negative voltage. check the connections on the meter or test a battery or other known supply ?

  • administrators

    @Danal said in Fried all the stepper drivers 😞:

    @SYCO said in Fried all the stepper drivers 😞:

    Anyone know why this would happen?

    Reverse polarity is the first suspect. Or the PS was really a lot more than 24V (more than 35, probably). Check it with a voltmeter before using it again.

    Only reverse polarity or a very substantial over-voltage would be likely to fry all the drivers on a Maestro together.

    I have known Duets survive reverse polarity - it depends on the short-circuit current limit of the PSU and which Duet (the WiFi/Ethernet can handle more reverse current than the Maestro, and Duet 3 even more).

    Can you still communicate with the Duet over USB? If so then it's likely that only the stepper drivers need to be replaced.

  • @dc42 thanks, any advice on what to test? Also could you link me to the right chips to order? Do you offer a repair service? I’ve ordered another for now but would like to get this working again.

  • administrators

    If you can communicate with the Duet over USB and Ethernet, and nothing other than the driver chips looks burned, then I think it's unlikely that anything is damaged apart from the drivers. The built-in 5V regulator is protected against reverse polarity. Reverse polarity for an extended period of time with a bed heater connected would overheat the bed heater mosfet, but if you noticed the smoke within a few seconds then that's unlikely.

    The driver chip part number is TMC2224-LA.

  • So I did some checks, and I can't connect to it over USB.
    But I figured out what I'd done, the mains input negative was connected to the negative out on the 24V side, and the negative connection to the Duet was connected to the PSU input side. Somehow got the two swapped over.

    So I guess I've grounded the PSU through the ground on the Duet. I had turned the PSU on a couple of times before it blow the steppers. Is this going to irreparable? I can't see any other burnt out components. I have downloaded the schematic for the 12-24V input to test the components.

  • administrators

    Ouch! I think you've put mains voltage into your Duet. It's unlikely that much has survived. I guess there is a chance that the bown stepper drivers have protected the rest.

    If you have access to SMD hot air equipment, then you could remove all the stepper drivers, as they are obviously blown and may be shorting out the 3.3V supply. The apply USB power, and see whether the red 5V and green 3.3V LEDs light up. If they do, but the Duet doesn't appear as a USB device to the PC, try putting a jumper over the Erase pins ands press Reset, then see if the Bossa port appears on the PC.

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