blown wifi module worth repairing



  • Hi

    I have a duet wifi with it's wifi module blown. I am sure it has the magic smoke released because I could smell it. The rf can smells of burnt electronics.

    Is the usb connection powered by the wifi module or the cpu?

    If so is there another way I can determine if the cpu is dead?

    I do have access to equivalent of ft232rl module and a 20mhz bandwidth scope.

    I did try probing the crystal I did seem to get a waveform so am guessing it maybe still alive?

    If we deem it's worth repairing, I can replace the wifi module with Ethernet module right?



  • @ageis
    :Is the usb connection powered by the wifi module or the cpu?<

    CPU



  • OH thanks. I think it's cactus then because I don't get the usual device detected jazz when I plug it into my laptop without 12v power.



  • @ageis Check U3.



  • what exactly is u3? hmm I doubt I be able to solder that. It's smaller then a little finger! Time to ask a favour from my engineer friend



  • @ageis I believe it supplies the 3.3v. There may be other damage not visible.



  • is there a schematic for duet wifi 1.2? I can't find it on here
    https://duet3d.dozuki.com/Wiki/Hardware_Overview#Section_PCB_revision_history


  • administrators

    The link to the schematic is in https://duet3d.dozuki.com/Wiki/Hardware_Overview#Section_Open_Source.

    Your first step is to check that the 3.3V rail is stable. If so, erase the firmware, reset, and see if the Bossa USB port appears on your PC.



  • I think the power supply fgor the 3.3v reg is cactus or at least critical bits of it like the two inductors they look dodgy. I dont trust it.

    Can I suck off the 3.3v regulator then feed 3.3v from a psu then connect the usb cable?


  • administrators

    @ageis said in blown wifi module worth repairing:

    I think the power supply fgor the 3.3v reg is cactus or at least critical bits of it like the two inductors they look dodgy. I dont trust it.

    Can I suck off the 3.3v regulator then feed 3.3v from a psu then connect the usb cable?

    Yes you can try that. You can feed 3.3v in through an endstop connector or the Z probe connector.



  • Might be worth checking if 5 or 3.3v rails are shorted to ground as a result of whatever failed before connecting external power, as that is a common failure mode



  • @bearer said in blown wifi module worth repairing:

    h checking if 5 or 3.3v rails are shorted to ground as a result of whatever failed before connecting external power, as that is a common failure mo

    ok can anyone think of likely scenarios I could of done this. I was waiting for the bed to heat up. all of a sudden puff I could smell magic smoke. I immediately switched the power off.

    I just cheked, the 5v rail isn't shorted but the 3.3v rail is. I have already desoldered the esp8266 and the 3.3v ldo. So I reckon mr processor is "well done". Very low resistence few ohms. no bueno

    I remeber watching a youtube video about finding shorts. He used a multimeter then probed around the board till he found the lowest resistence. Do you need an expensve mutlimeter to do that? I probed a few points they all appear to be 13.5 ohms


  • administrators

    @ageis said in blown wifi module worth repairing:

    @bearer said in blown wifi module worth repairing:

    h checking if 5 or 3.3v rails are shorted to ground as a result of whatever failed before connecting external power, as that is a common failure mo

    ok can anyone think of likely scenarios I could of done this. I was waiting for the bed to heat up. all of a sudden puff I could smell magic smoke. I immediately switched the power off.

    As @Stephen6309, check whether U3 looks damaged. It's the small square chip near the VIN terminals. We've had a number of unexplained U3 failures recently, maybe there was bad batch of chips. If it's a genuine Duet, U3 failures normally qualify for replacement under warranty.



  • it does look burned. Excellent warrenty cover. I doubt damage to the pads around the vin screw conector is covered.

    Thanks for your help david. I will get myself so real kapton tape then attempt to repair it. At least it didn't set on fire. It does when you hold a lighter to it though.

    I always been interested in smd. I am jelious of al the engineers who able to do it.


  • administrators

    @ageis said in blown wifi module worth repairing:

    it does look burned. Excellent warrenty cover. I doubt damage to the pads around the vin screw conector is covered.

    Thanks for your help david. I will get myself so real kapton tape then attempt to repair it. At least it didn't set on fire. It does when you hold a lighter to it though.

    I always been interested in smd. I am jelious of al the engineers who able to do it.

    If it's a genuine Duet, ask your supplier to replace it under warranty.


Log in to reply