The power regulators are ‘buck converters’ with very fine pitch parts at their heart. It is extremely hard to replace those. I have done it a few times and as surface mount rework goes, of which I have extreme experience, I can say that unless you have experienced SMT rework ability I would not try to replace the part.
Lets instead try something by removing a part that we have rarely found can breakdown and lead to the supply not starting because of overcurrent due to a protection diode failure. Because this is the 12V aux supply that goes nowhere this is a low risk thing to try AND we have seen this at least once so there is ‘some chance’ it may work. Not guarenteed but it could be your fastest way to a fix.
IF you feel ok with trying this then do NOT plug in your lidar after the fix until you determine if this has solved the problem and 12V Aux works again. This is the very 1st thing I would try myself as it has some limited history as being the issue. Not a certainty.
FIRST OF ALL DO NOT TRY THIS WITHOUT REMOVAL OF THE RED POWER LEAD FROM THE BATTERY FOR SAFETY!
If and only if you have a SMT rework station with high temp hot air reflow then try this. If not we will discuss other approaches but this is your fastest way to address this so let me know.
Completely take out the batteries so they dont fall over when you try this. Then stand the magni up on the floor with the front of the magni on the floor. This makes the MCB back face upward.
You will have to locate D1403 which is a rather big SMT Zener diode. This part is on the back of the board fairly close to the center area but just above center. If you have a SMT rework heat gun with 5 - 10cm airgun tip this would be not too hard. D1403 is on the back and is if you looked at the back of the MCB this large diode is 5mm below the JTAG201 5-pin jack so you cannot miss this, it is easy to find and see if you have tilted the Magni like I suggest.
If you do NOT have such a heat gun it would be much more tricky. Try not to point the heat at the capacitor next to it and point the heat more towards the JTAG201 jack. You need high enough heat to melt the leadless solder so you need around 280 to 300 deg C. Many rework stations show temp in F so be aware of that.
If you are not comfortable with this we can talk more for other longer lead times ways to solve this issue.
IF you do this verify 12V aux is working WITHOUT YOUR LIDAR and only after that try the lidar again.
Attaching a picture with MCB in a Magni as I have described.