Magic smoke and stopped working

[hiro_ono]

I connected my printer (duet ethernet, 12V) for the first time in a while, and couldn't find it on my browser, i plugged in a USB cable (stupidly with the printer still powered on) and there was some magic smoke. the ethernet light isn't on, and when i connect via usb i can't see it. Any help fixing it would be great

[A Former User]

see this guide https://duet3d.dozuki.com/Wiki/What_to_do_if_your_Duet_won't_respond

in particular the bits with removing the sd card and the status of the leds when connecting with usb

[hiro_ono]

I have no green 3.3v led, removing the end stops didn't fix it

[hiro_ono]

diag led also not lit

[A Former User]

Hmm. Doesn't bode well. However in itself connecting the USB cable with the printer on shouldn't cause smoke, of either plain or magic origin, so it would suggest something wrong with wiring or possible the mechanical forces caused something to short?

Did you spot where the smoke signal originated? Is there any visible damage on the board (if unsure, feel free to upload a clear picture of the board). Especially the circled area:

[hiro_ono]

@bearer I've just gone out but I'll send a picture in a bit. but the pins on the usb cable were pretty ruined, and the plastic around it was melted

[droftarts]

@hiro_ono There shouldn't generally be any problem plugging in the USB cable while the printer is turned on; I do it fairly frequently! Could you have put the cable in the wrong way up? It is possible, with enough force.

Ian

[A Former User]

Melting plastic suggest large currents, large and slow fuses if any. Also take a look at fuse F3, with a bit a lot of luck it might have saved (some of) your bacon but given it doesn't work with just USB is a bad sign - but could be the usb port also got damaged.

Do take some pictures before removing any wiring, could be key to finding out what caused the failure which you really want to get to the bottom of before putting a new board in there.

[boldnuts]

@bearer I am thinking ground loop unfortunately

[dc42]

@droftarts said in Magic smoke and stopped working:

@hiro_ono There shouldn't generally be any problem plugging in the USB cable while the printer is turned on

There is if the ground connection between the Duet VIN terminal block and the PSU isn't solid. The ground circuit gets completed by mains ground and the USB cable instead. USB cables and connectors don't take kindly to having the bed heater current run through them.

[hiro_ono]

Here's a couple of pictures

[hiro_ono]

I think U2 might be the problem? looks a bit odd and is hot to the touch, not hot enough to burn me

[hiro_ono]

I've looked up the part and it appears to be a 3.3V regulator, so that would make sense. I don't have a hot air gun but have a lot of experience soldering (although never surface mount) am i likely to be able to replace it?

[A Former User]

@hiro_ono said in Magic smoke and stopped working:

I've looked up the part and it appears to be a 3.3V regulator, so that would make sense. I don't have a hot air gun but have a lot of experience soldering (although never surface mount) am i likely to be able to replace it?

U2 is definitvely toast, and correctly identified as a 3.3v regulator. Due to the multiple layers and double copper thickness of the boards its really not easy to solder without both a preheater and hot air or infrared heating. There are a few dirty tricks that can make it less hard, but its also not without risks.

[A Former User]

also see if you can get a close up of this area, without the shade

[hiro_ono]

[hiro_ono]

@bearer Thats a pain, are there any places where they can fix this sort of thing? I have a friend with a reflow station but I'm not sure how fancy it is

[A Former User]

Would depend on where you're located I guess. But a hot air rework station might get the job done if you take the time to "soak" the board and get the whole area up to 100-120C for 2-3 minutes before trying to remove the part. Or stick it in the oven to preheat it; or cut off the legs leaving you with only the tab to desolder with an iron.

As you don't need to salvage the part the main concern is to avoid lifting traces and pads.

[A Former User]

Oh, and yeah, the USB port might need replacing as well, current clearly took the path through the ground lead there.

[hiro_ono]

Ah that's a bummer, any idea what could've caused it in the first place? Don't want to get it fixed and then plug it in for the same thing to happen