So in preparation to install a fan mount for printing PLA, I was testing voltages output by the pins on the RAMBO.
I guess I accidentally shorted the pins on FAN 2 (shown in the figure below) and heard a pop.
After plugging the fan back in and flipping the power switch the fan just ‘twitches’ and LED 8 (shown in the schematic below), pulsates in sequence with the fan.
Testing revealed that the internal diode of the IRLML6346TRPbF (Q8 in the schematic) is blown.

Does anyone know or can think of a work-around for this?
Does anyone know how to re-purpose FAN 1 to function as FAN 2 did?
*note: section in question is in the ‘MOSFETS’ portion of the schematic

I don’t really possess the equipment needed to replace the MOSFET itself.

Pictoral diagram:


thanks all.

Can you use the first Fan connector near the hot end connector? If you can’t use that channel, you can always power the fan off the same case fan connector, or directly from the power supply.

I tried plugging in to the first fan connector as you suggested, but the fan doesn’t turn on. (I’m not sure if there is a way to change this in settings or not)

you can always power the fan off the same case fan connector

I’m not sure what you mean by this

The right pin of the FAN2 connector still outputs 24v when turned on, but if I ground the fan directly to the case ground there is 24V and 3A running through a 12V 0.08A fan (i.e. Loud and overworked :open_mouth: )

You can change the pin assignment in Pins.h. We’ve also limited some of the power going to the fans in the newer firmware, to allow for 12V fans to be used with the 24V firmware. You may also want to consider replacing the mosfet on the board, or even placing a new mosfet directly over the existing one and just bridging the connectors to the pins/pads below.

I ended up replacing the mosfet on the board.
Fan works as it originally did now!

thanks for your help.