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Hello I'm new to 3D printing and have against my better judgement decided to build a Rostock Max v3 from a kit as my first printer and can't seem to get it to work first the hot end wouldn't work then I fixed that then the fan in front on the thermal wouldn't work I got a replacement fan but when I tried to test if it now works the machine wouldn't power on

Sorryyouarehavingaproblem maybeelaborateonwhathappenswhenyouflickontheswitch

Nothing happens, the Rambo board doesn't power on, the first time I powered It on the machine activated for about a second then shut off

Welcome to the forums Jim. We're happy to help, and try to get things working to the point where you're happy with the printer.

Any information you can give us on what isn't working, or what happens helps us help you. It sounds like you blew the logic/fan fuse, but that's all I can think of at the moment.

As an aside, Joe, I think you may need a new space bar. Either that, or lay off on the coffee/soda/meth/sugar while you still have teeth

I also think it's a fuse failure. The board wouldn't even start up if I plug it into USB, but my laptop recognizes that it was plugged in. The question is now why did the fuse fail, I checked the wiring and found nothing, all the wires are were they should be.

As a note, the modern RAMBO cannot be powered over USB, as the easiest way to fix an issue they were having with earlier designs, so it never will be powered over USB

If you have a multimeter, I would check the resistance of everything on the fan connectors, as well as looking for a bridge on any soldering you've done. Generally, the equivalent resistance of the fans should be fairly high, as they draw relatively little power.

I checked the connectors, they have high resistances like you said. And here's a picture of the hotend Pcb maybe it could help