Is there likely a way to repair a blown PWM output?
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Easy enough to fix with care. Hot air rework station would be the best way, however you can use a soldering iron with patience. I replaced the entire micro on my board, a 3 pin FET is just a walk in the park. I guess years of experience helps. Flux is key to soldering the part back correctly, Some really good stuff on YouTube for this, and sadly some bad stuff to.
Jeff
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The tricky part is removing the blown MOSFET. It's easy with a hot air rework station, difficult otherwise. Soldering the replacement MOSFET can be done using an ordinary soldering iron with a fine tipped bit.
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I do have soldering station with hot air luckily, whether or not I can get the SMD MOSFET locally or have to order online is the question.
Online it seems..
@dc42 can you please confirm this is a suitable replacement?
http://au.element14.com/nxp/pmv40un2/mosfet-n-ch-30v-4-4a-sot-23-3/dp/2469654And how I can confirm if thats the part that would have blown?
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The part is a PMV40UN2 so that's spot on.
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Good you have the hot air rework station, personally I don't even attempt to do SMD work without. I prefer about a 1mm wide chisel tip. Too pointy and they do nothing good. Flux flux flux. Clean up with some 91% + iso and all is well.
Also learning the art of drag soldering is always a good skill, not useful in this case but sure comes in handy.
Jeff
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Ohh, a bit of kapton tape covering areas you don't want melting is a useful trick. If you have plastic connectors too close for example, cover them loosely with kapton. More or less make a heat shield.
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Good thing it happened to Brian and not to me. My thick fingers would have a great deal of trouble over this. Besides, all I have is a small soldering iron. He is the electronics I am mechanical. Good split.
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So, what is the correct orientation for the flyback diode? I'm getting ready to connect a Berd-Air also and the orientation discrepancies have me nervous. I would rather not get lucky…
It would be great if the Wiki page could be updated. https://duet3d.com/wiki/Connecting_and_configuring_fans
Thanks!
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The wiki page already mentioned the need for a flyback diode, but I've just updated the text with information about the polarity.
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If you have a microscope, it would make the job a lot easier!
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I find a pair of strong reading glasses sufficient during soldering, supplemented by an eyeglass for inspecting the joints after soldering.
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If you have a microscope, it would make the job a lot easier!
I find that to be too much mag in most cases. Great for final inspection however.
