Messed up kinda bad after a few short circuits



  • Okay, first off i have had the latest revision of the duet wifi for a month or two now and i originally had it set up with RGB lighting in the two spare PWM fan outputs and one in the spare heater. then one day my cheap 5015 fan decided that it had had enough and the two wires broke off and shorted mid-print and killed PWM 0 so i sacrificed one of my RBG colours to reassign the fan.

    fast forward to today i thought it would be a great idea to do some long needed cable management and tweak my lighting. while trying to crush the LED strip into the aluminium extrusion i must have nicked the wire track and had another short on the 24v PWM so now i only have one working and i have run out of 24v LED strips. no biggie the board still works.

    then i remember i had some 5v LED strips kicking about from another project and decide to see if i can hook it up to one of the 5v outputs extra on the board so i rig it to the two furthest left pins on the SD connector port (ground / 5v from the wiring diagram) up off the machine and its working good, awesome. then on the build back up my stupid ass done the exact same thing as before and nickled it, shorting it again only this time i see smoke coming from the board so i shut everything down.

    after stripping the board and looking for damage i dont see any so i decide to plug it into the USB of my PC.
    the smoke happens again after a few seconds and i only get 2 lights on the front, one from the 5v and one near the rest button. the board doesnt power anymore and im not sure where to go from here ( my bltouch doesnt kick in, the wifi module doesnt light up, etc)

    after a few seconds of being plugged in through USB the L1 inductor heated up so much when i touched it for a second it burnt me pretty bad. i know for sure i have blown two mosfets and maybe the L1 inductor thing but other than that i have no idea where to go from here?

    would anyone be able to repair this for me or maybe guide me on steps i have to do? (i will gladly pay, its probably cheaper than replacing the whole board)
    i am pretty good at putting my hand to stuff so i might be able to attempt it myself but would feel ALOT better if a more experienced person did as its not exactly the cheapest thing

    Thanks and sorry for the long read and thanks in advance for any help


  • administrators

    I'm sorry, it's likely that multiple components have failed on the Duet. It sounds like you had a short between +24V and +5V or +3.3V. That will probably have blown the processor, the 3.3v regulator, the WiFi module, and several other chips powered from +3.3V and +5V. Maybe also the stepper drivers. If L1 is getting hot then I guess the 5V switching regulator chip is blown too.



  • @dc42 said in Messed up kinda bad after a few short circuits:

    I'm sorry, it's likely that multiple components have failed on the Duet. It sounds like you had a short between +24V and +5V or +3.3V. That will probably have blown the processor, the 3.3v regulator, the WiFi module, and several other chips powered from +3.3V and +5V. Maybe also the stepper drivers. If L1 is getting hot then I guess the 5V switching regulator chip is blown too.

    Ah, damn. That's what I feared. Oh well you live and you learn I guess, sometimes the hard way haha. What I dont understand though is I never worked on both the 5v and 24v leds simultaneously so I have no idea how I could have managed to feed 24v into the 5v. I was maybe being a bit haphazard and careless but after reading its nearly impossible to kill the board unless you short 24v into 5v I was maybe a bit overconfident thinking there is no way I could do that haha. Both sets of LEDs were working when I powered on initially just when I flexed the machine it cause an arc on the strip. The only thing I can think maybe has happened is that one of my jumpers had come off on the board and touched the 24v? That's the only possible way I can think of but I just wanna make sure I have exhausted all possibilities before sinking £££ into a new board. I'm guessing the fact that the wifi module doesn't power anymore is an obvious sign of fried components?


  • administrators

    @flyinchinchy, the fact that the 3.3V green LED doesn't light indicates that there is no 3.3V power. So either the 3.3V regulator U2 has failed, or one of the components powered from 3.3V has failed and is shorting the 3.3v rail out, or both. This is in addition to the probable failure of U3 and/or D2 (because L1 is getting hot).



  • @dc42 ah, tbh I was just clutching at straws hoping there would be some way to fix it (within reason). The 3.3v green LED actually does light up but only for about 2-3 seconds then fades away so it's probably still shorting as you said. I think in going to need to call it a day, as I don't think I have the skillset & tools required to do a proper diagnosis and repair and we could probably be here all day trying to guess what has blown. It's a shame because it really is the best board I have used, just a pity I was so reckless, oh well! Thank you anyways for your help so far though



  • One thing that you can do to avoid mistakes is getting a short-protected power supply and running secondary stuff off of cheap step-down converters connected directly to the power supply.



  • I tell you what, wiring the makerbot led end stops was a little hairy, wired totally different and if I'm not mistaken easy to short power to ground.

    I'm curious what could blow if one makes that mistake.

    Sad to see a board go pop, been there with a R/C esc, second use I plugged it in wrong and nuked it, $120 mistake, right at the start of a race.



  • Generally, power to ground results in no damage. The power supplies are fused/overload protected.


 

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