Chip at U3 up in smoke



  • On our Duet 3D v1.0.4 board, the chip at U3 went up in smoke and the text on it is no longer readable. It may have the label 4403T based upon photos of other boards.

    Just a few seconds before the smoke we heard the Y axis dual steppers start oscillating as if jammed and couldn't get power killed fast enough to save it. We don't feel any jam in the motors or the tracks when turning the shafts by hand and there's no debris in the tracks to explain this. But we're not 100% sure if a motor stall caused the chip to fry or the stall/chatter was just a side effect of the chip failing. Which was cause and which was effect, in other words. We believe the motors themselves are properly compatible and everything has been working well for a few weeks before this.

    Any ideas about what could cause this?

    We have two additional backup boards on order for delivery tomorrow so we won't be down too long. We are having trouble clearly identifying this chip online (maybe it is 4403T-1432-883L?).

    Does anyone think we could replace this with precision soldering equipment? Could there another failure related to this even if we did replace it?

    Thank you for reading and for any help you can provide! We'd hate to put a new board in and fry it too.



  • U3 is the Vin to 5v converter, most common cause of letting the smoke out on that is a short somewhere (wiring, or a peripheral device) from Vin to +5v.

    No problem replacing it if you have a hot air rework station, but the voltage transient may have caused damage to other chips. Wouldn't hurt to try swapping U3 though, they're cheap:

    https://www.digikey.com/product-detail/en/allegro-microsystems-llc/A4403GEUTR-T/620-1273-1-ND/1987530



  • @elmoret Thank you.... you were right. There was a loose copper strand in the connector to the servo touching across power and ground and leading to a short.


Log in to reply