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My Max V2 has been nothing but a pain. After the thermistor popping out of the hot end and me melting and ruining two hot end assemblies now while waiting for it to get up to temp (225) it reached the temp and then gave me an error saying the sensor failed. About two minutes later the display went black and upon investigation it turns out the Rambo board is dead. It has power to it but nothing is working. I have yet to get a successful print of the fan shroud which is the first thing I've tried to print. Now it's dead. I had great hopes for this design over the other printers I have. Anybody got any ideals on what could of happened to the Rambo? I had just ordered the E3D (6) hot end because it has a screw to hold in the thermistor, but now I can't even use it.

Check the fuses on the RAMBO, there are 3 of them.
But I'd check your wiring before powering on again, it sounds to me like you have an intermittent short. If your lucky it just blew a fuse.

Sensor failed means either the thermistor read a very high or very low resistance, the fact the logic circuit lost power most likely means it was shorted, possibly with the Hotend power line, if that is the case you may have damaged the thermistor input.

Thanks. Where are the three fuses located? I see only the big 15 amp one.

The small fuses are located behind the power connector and below the power connector.

The Fuses are NANO2 type. If the problem is a fuse it is most likely F2.

CHECK ALL WIRING FOR SHORTS - ESPECIALLY THE MOTOR WIRING BEFORE CHANGNG THE FUSE.

nitewatchman

Found the fuses and it is F2. Are these available at Radio Shack?

bertropro wrote:Found the fuses and it is F2. Are these available at Radio Shack?

No you'll have to order one from mouser, digikey, or I think ultimachine carry them
Or if you're very careful, you can solder wires to the holder and use a more readily available fuse/holder.

I blew one of mine, very early on, there is a post somewhere with the part numbers.

But as was said above, you really want to know why it blew first, so do check all of your wiring carefully.

https://ultimachine.com/content/fuse-0448005mr

Look for wire whiskers that may have escaped the pin when the extruder plug was crimped on. Check the extruder motor wires where they enter and exit the aluminum columns for cut or chaffed wires. Also look at the fan connection that you soldered to the board, it also runs on the Rambo P/s.

May also be that the fuse was just touched by the finger of God and died. Everything else other that the motors, Rambo cooling fan and Rambo logic is on the other fuses.

nitewatchman

The thermistor wiring is also on that circuit.

Thanks you guys. I'm somewhat embarrassed that I didn't see the fuses. I kept glancing over them thinking they were chip capacitors. Anyway I found them online and ordered some. Once again thanks for your help.

Polygonhell wrote: Or if you're very careful, you can solder wires to the holder and use a more readily available fuse/holder.

Way better to solder the alternate fuseholder wires to the blown fuse in such a way that you can simply reinsert the fuse rather than risk messing up the board. If you screw it up, that fuse was dead anyway.

Yes, if your handy with a iron I agree solder a socket for automotive blade type fuses in place. So easy to source and allows for a easy run to nearly anywhere to get what your after at almost any time of day.