Just wanted to update everyone and say a huge thanks to everyone that's commented. I'm still weighing my options about going forward and at the very least considering a few options going forward.

1: Depending on cost/lead time for a refurb board, perhaps go that route. I'll be honest about the fact that I'm a bit impatient and I was very excited to have a multi-year long project come together and work (albeit briefly). It's a large format build with a lot of bells and whistles that I don't have on other 3D printers, so I was very excited to see it move and have a decent amount of success printing.

2: Remove U3, and run an external 5V power supply. At this point, I'm somewhat leaning toward this option since I am running a BLTouch probe, and based on what I've read, they can be the cause of 5V failures. Having an external 5V source would likely afford me some more headroom, and additional cooling potential, since it's not located in a heavily populated area on the board. I'm also really not running much off 5V (Just BLTouch) since I have 24V fans. And as everyone has said, removal is generally easier than re-attachment.

3: Remove and replace. I do have some concerns about repair; just due to the board's age and the fact it's a slightly older revision. Looking through some of the revision notes, it seems the newer 1.04b and c revisions did have some improvements to the 5V circuitry, so that slightly pushes me away from the replace U3 option and toward external 5v or refurb. I'm not going to say I'm 100% confident in my ability to remove and replace the chip, but in general I would classify myself as mostly competent with soldering.

At this point, I'd lean toward option 2, but that's without an idea of lead-time and cost of a refurb. I know Duet is based in the UK, and shipping time to the US is either cheap or fast; not usually both.

Just wanted to update everyone and say a huge thanks to everyone that's commented. I'm still weighing my options about going forward and at the very least considering a few options going forward.

1: Depending on cost/lead time for a refurb board, perhaps go that route. I'll be honest about the fact that I'm a bit impatient and I was very excited to have a multi-year long project come together and work (albeit briefly). It's a large format build with a lot of bells and whistles that I don't have on other 3D printers, so I was very excited to see it move and have a decent amount of success printing.

2: Remove U3, and run an external 5V power supply. At this point, I'm somewhat leaning toward this option since I am running a BLTouch probe, and based on what I've read, they can be the cause of 5V failures. Having an external 5V source would likely afford me some more headroom, and additional cooling potential, since it's not located in a heavily populated area on the board. I'm also really not running much off 5V (Just BLTouch) since I have 24V fans. And as everyone has said, removal is generally easier than re-attachment.

3: Remove and replace. I do have some concerns about repair; just due to the board's age and the fact it's a slightly older revision. Looking through some of the revision notes, it seems the newer 1.04b and c revisions did have some improvements to the 5V circuitry, so that slightly pushes me away from the replace U3 option and toward external 5v or refurb. I'm not going to say I'm 100% confident in my ability to remove and replace the chip, but in general I would classify myself as mostly competent with soldering.

At this point, I'd lean toward option 2, but that's without an idea of lead-time and cost of a refurb. I know Duet is based in the UK, and shipping time to the US is either cheap or fast; not usually both.

Or rather, I'm dumb and forgot how electricity works. If U3 is internally shorting, that's obviously what a measurement of D2 when it's still attached would show.

So, based on the advice from this thread:

https://forum.duet3d.com/topic/6462/u3-burned-a-hole-in-itself

Specifically referring to DC42's speculation that if D2 failed open or short, it would likely take the U3 with it. I've checked D2, and it appears shorted. With my (admittedly cheap) DMM in resistance/diode test mode, shows as shorted; same readings with both polarities. Doing a sanity check with another diode, it shows different readings depending on the DMM polarity, so I do at least somewhat trust the DMM reading.

So that somewhat changes the question. With the board isolated,I'm unable to find any wires/stray pieces of metal shorting the +5V circuit to ground, but there is continuity between the 5V pin and ground. I've double and triple checked and can't find any external shorts. So I suspect I can't use external 5V since there is still an internal short somewhere. Any thoughts other than a D2 + U3 replacement? Is there any other component to test? I'm pretty useless at reading circuit diagrams to determine test points.

Hello,

I recently got my Duet 2 Wifi up and running, and after probably about 5 hours of use, it appears as thought the U3 module (5v step down regulator) appears to have bitten the dust. There is a burn mark on the surface of the chip, and the 5V and 3.3V LED's are not illuminated while the Vin (24V) is illuminated. Later today, I'm likely going to try and track down what I suspect is a short somewhere in the system based on other forum posts I've seen.

Unfortunately, the Duet was bought back in 2018 even though I just opened it and started using it last week. Unfortunately for me, this means a warranty exchange is out of the question. So I'm wondering what the best course of action is for me going forward. I'd prefer to not buy another Duet if I can avoid it. Does it make more sense to try to replace the chip itself, or use an external 5V in source?

I'm also wondering if there are any other concerns if that U3 module does fail; are there other things that are likely to fail at the same time? Are there any long term concerns with running an external 5V in source?