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  1. Following the previous chapter, you have to connect extruder motors in a specific order. Otherwise, it will be complicated to troubleshoot any issues.
    • Following the previous chapter, you have to connect extruder motors in a specific order. Otherwise, it will be complicated to troubleshoot any issues.

    • !!! CAUTION, the board is very sensitive to electrostatic discharge (ESD), please proceed with caution and do not touch the chips on the board !!!

    • Each port on the board is labeled with a letter E and a number, the proper order is as follows:

    • Port E0 - Extruder 1

    • Port E1 - Extruder 2

    • Port E2 - Extruder 3

    • Port E3 - Extruder 4

    • The board is in the box "MOTORS & MULTIPLEXER".

  2. M3x10 screws (3x) Stepper Switch case (1x)
    • M3x10 screws (3x)

    • Stepper Switch case (1x)

    • Stepper Switch board (1x)

    • Place the board into the case and secure it with two M3x10 screws. You will use the same screws to mount the case on the frame, so don't tighten them fully now.

    • Use 2.5mm Allen key.

    • The printed parts are in the bag 4.ELECTRONICS.

    • Starting mid of August 2017 the case will be shipped in black colour only, the function and assembly are the same.

  3. M3x10 screws (2x) Find the drilled holes on the frame (above Rambo cover).
    • M3x10 screws (2x)

    • Find the drilled holes on the frame (above Rambo cover).

    • Place the case in a way, that the "UP" sign is facing upwards.

    • Tighten the screws fully using the 2.5mm Allen key.

    • When tightening proceed with caution, if you use an excessive force and miss the hole in the frame you can break the screw.

    • Note that if you have MK2 printer, your multiplexer cables will be entering from the side of the RAMBO cover and not from above.

  4. Following the previous chapter, you have to connect extruder motors in a specific order. Otherwise, it will be complicated to troubleshoot any issues. Start with the Extruder 1 (closest to the case), take the cable, locate the proper connector and connect it. Ensure it is plugged all the way in!
    • Following the previous chapter, you have to connect extruder motors in a specific order. Otherwise, it will be complicated to troubleshoot any issues.

    • Start with the Extruder 1 (closest to the case), take the cable, locate the proper connector and connect it. Ensure it is plugged all the way in!

    • Reminder: the proper order of the extruders is following (see the last picture):

    • Port E0 - Extruder 1

    • Port E1 - Extruder 2

    • Port E2 - Extruder 3

    • Port E3 - Extruder 4

  5. Use zip ties to manage the cables outside the Stepper Switch case. Two are enough. Use the inner volume of the Stepper Switch case to manage cables from all extruders.  Arrange them similarly as shown with the arrows.
    • Use zip ties to manage the cables outside the Stepper Switch case. Two are enough.

    • Use the inner volume of the Stepper Switch case to manage cables from all extruders. Arrange them similarly as shown with the arrows.

    • Don't cover these two ports with the cables from extruders!

  6. For connecting the Stepper Switch board and the Rambo board, there are two cables prepared. The difference between them is the number of pins in the connector.
    • For connecting the Stepper Switch board and the Rambo board, there are two cables prepared. The difference between them is the number of pins in the connector.

    • Cable nr. 1: 5 pins on one end and 4 pins on the other

    • Cable nr. 2: 4 pins on both ends

    • The case cover is not necessary in this step, it is used to increase the cable visibility.

  7. Take the cable with 4-pin connectors on both ends and connect it to the Stepper Switch board. Proceed to the other end of the cable and connect the 4-pin connector to the Rambo board as shown in the picture.
    • Take the cable with 4-pin connectors on both ends and connect it to the Stepper Switch board.

    • Proceed to the other end of the cable and connect the 4-pin connector to the Rambo board as shown in the picture.

    • Ensure the connectors are plugged all the way in on both ends!

    • Use the opening in the bottom of the case to guide the cable.

  8. Take the cable with 5-pin connector on one end and connect it to the Stepper Switch board. Proceed to the other end of the cable and connect the 4-pin connector to the upper row of 2x 5 pin socket as shown in the picture (RED wire is on the right facing "out" from the board). Ensure the connectors are plugged all the way in on both ends!
    • Take the cable with 5-pin connector on one end and connect it to the Stepper Switch board.

    • Proceed to the other end of the cable and connect the 4-pin connector to the upper row of 2x 5 pin socket as shown in the picture (RED wire is on the right facing "out" from the board).

    • Ensure the connectors are plugged all the way in on both ends!

    • Use the opening in the bottom of the case to guide the cable.

    • Close the case using the cover and M3x10 screw.

  9. In this step we will finish the Rambo electronics, take all the cables from the multiplexer and connect them as shown in the picture. Multiplexer thermistor (cable going from the Multiplexer labeled with Yellow/Green heat shrink) [Orientation does not matter]. Left hotend fan (cable going from the Multiplexer labeled with Blue heat shrink).
    • In this step we will finish the Rambo electronics, take all the cables from the multiplexer and connect them as shown in the picture.

    • Multiplexer thermistor (cable going from the Multiplexer labeled with Yellow/Green heat shrink) [Orientation does not matter].

    • Left hotend fan (cable going from the Multiplexer labeled with Blue heat shrink).

    • Front print fan (cable going from the Multiplexer labeled with Red heat shrink)[make sure that the red wire is closer to the thermistor].

    • P.I.N.D.A. probe

    • Multiplexer heater

    • DOUBLE CHECK the connection! It is very important to ensure the correct connections!

  10. When all the cables are plugged, close the Rambo cover and tighten the screw M3x40 (1x). When all the cables are plugged, close the Rambo cover and tighten the screw M3x40 (1x).
    • When all the cables are plugged, close the Rambo cover and tighten the screw M3x40 (1x).

  11. Electronics are done! Let's move to the next chapter. Starting November 2017 the Multi Material upgrade is shipped with new spool holders.
Finish Line

71 other people completed this guide.

Jakub Dolezal

Member since: 02/20/2017

214 Guides authored

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Prusa Research Member of Prusa Research

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7 Comments

We are having problem with the stepped motor running in reverse. Could you please give us some advices? We followed every instruction step. Thank you!

Hoang Duc Trung - Reply

It sounds like you accidently switched the position of a motor in the Stepper Switch Board (I.E, Extruder 1 and 2 are switched, or 3 and 4. These motors run in reverse of each other (as in E1 goes one way and E2 goes the other way). Check the wiring there.

Michael G. -

Hi Hoang,

please double check you wiring. Ensure cables are plug to the correct sockets and all the way in.

Jakub Dolezal -

I’m having some problems when i tell the motors to load filament m1 is fine but when i tell m2 to load it unloads m1 and when i tell it to load m3 it loads m1 and when i tell it to load m4 it unloads m1.

I’ve checked all connections 3 times and flashed the correct firmware 3 times and it still doesn’t work any help would be appreciated please.

jonathan tims - Reply

I have the same problem. How can I solve t?

Daniel Han -

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