Is there likely a way to repair a blown PWM output?

dc42

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.

briangilbert

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/2469654

And how I can confirm if thats the part that would have blown?

T3P3Tony

The part is a PMV40UN2 so that's spot on.

InSanity

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

InSanity

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.

Zesty_Lykle

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.

gen2eng

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!

dc42

The wiki page already mentioned the need for a flyback diode, but I've just updated the text with information about the polarity.

ShadowX

If you have a microscope, it would make the job a lot easier!

dc42

I find a pair of strong reading glasses sufficient during soldering, supplemented by an eyeglass for inspecting the joints after soldering.

InSanity

@ShadowX:

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.