I burned my fan headers 😠but its ok now
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I wanted to test that my always on connector was getting 24v and I ended up shorted my multimeter leads together. Fans stopped working so i googled and found this thread. No continuity from Vin to VIN+, there was continuity from center jumper to V_FAN, so I made a jumper from VIN+ to VIN and it looks like it's working properly now.
I wanted to make the thread to let it be known that I'm another person that had this short happen, in case an abundance of people having similar things happen might make a fuse on that trace prudent in future revisions. Or maybe just a plain VIN+ to ground pin out for supplemental power without risking the whole fan bank.
I would have just chimed in on the previous thread but it sadly was closed.
Thank you dc42! I love my Duet 2 Wifi.
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It's actually amazing how many people try to measure voltage directly at the header and kill things.
I was one of those fools but it wasn't on the 'always on' line but on the fused switched fan header. Apparently silicon fuses faster than a fuse
I had a spare output so I moved the fan over for now .... -
@jens55 Yeah i think the proper way to have done it would have been to attach the negative lead to neutral somewhere FAAAAR away from the circuit board hahaha like maybe ground on the power supply. Still would have been easy to short those two pins though but less likely at least.
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If I am ever tempted again, I will make a connector that fits onto the header with two long leads. No bare test leads anywhere near the header!
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I find using one probe on either Vin or GND at the Vin terminal, and the other probe through the little "window" on the back of the shell that holds the terminals is the second best option for probing when the board is live.
Impossible (or damn near) to short the probes to each other and less chance of a single probe shorting the adjacent pin.
