Main board issues


Hi this is Pu from Rapyuta Robotics, I have 2 issues.

  1. we shorted the fuse and the USB port case by accident, and after that, the motor communication does not work, other communication works, like battery voltage, sonar. Do you have any idea how to repair? otherwise, we have to buy a new main board

  2. I replaced the 4.6 ver mainboard, others working fine, but when I tried to connect the sonar, I had a terrible short.

    a. I use a female-to-female cable same as ver 4.9 main board.
    b. maybe the male-to-male cable provided by you is flipped compare to ver 4.9
    c. it happened when the power is OFF
    d. pin9 / pin41 was burnt, but when I check the pin definition, pin9 is GND and pin41 is NC, even connector flipped, short should not happen.
    Do you have any idea?


I do not want to dig more about the old version board to be horniest, but we need a ver 5.0 board urgently.


If you’ve shorted the fuse you need to replace it. It is a very common and widely available fuse type.

You may have killed power to the motor without killing the power to computer. That would explain the symptoms you are seeing. Replace the fuse.

However if you’ve plugged the sonar cable incorrectly as it would appear from the second problem you’ve encountered you may have destroyed the main control board - if that’s the case you will have destroyed the controller, the main computer and many other components.


issue 1: the motor power is still there, I can not spin the motor by hand, but the communication from the motor to RPi is dead
issue 2: the main board is working still, but the cable burnt.
I understand your point, but it happened during POWER OFF, and PIN 9 is GND and PIN 41 is NOT connected according to “Magni_MCB_pinout”, that why I ask this.


When plugging in the Sonar board the entire power must be off, not just motor power. It is very important to not be plugging in or out the Sonar board when the battery is connected at all because the 24V runs right to that cable so pins that connect in unpredictable ways. More important is on the early pre-production boards the Sonar board cable was NOT keyed so it was also possible to plug the cable in off by one spot so it was very very important to check very carefully. Production units have a keyed connector but we tried to help customers by offering prototype units and the risks there are much greater for being off by one pin width with catastrphic results. On Rev 5.0 boards a fully keyed connector is also present to make it nearly impossible to plug in off of the center BUT ONE MUST NEVER PLUG IN SONAR BOARD WITH BATTERY CONNECTED AS THE 24V GOES TO MANY PINS THERE AND IT IS JUST TOO RISKY. Older rev 4.6 boards being prototypes had to be very carefully plugged in (still with ALL power disconnected from battery).


This does not appear to be the fault of the board. This may be due to assumptions made about the making of custom cables. Ubiquity Robotics uses cables where both ends are either male or female. If you mix a cable for a rev 4.9 sonar board that has a connector with male pins with a rev 4.7 or earlier board then no simple cable is possible. A cable with one end male and one end female pins will in effect swap the even and odd rows of pins. I suspect it is in doing that that has led to direct short of the high current power supply and that causes great damage. It is best to use either both rev 4.7 or 4.6 boards with rev 4.7 or 4.6 sonar boards so both ends are the older style cable with male pins on cable ends and female pins on both board connectors. When using rev 4.9 and beyond boards one must have both ends on the boards be male pin connectors.

Always and of course the final ‘buzz check’ with a real meter on the installed cable prior to power up for any custom cable is verify that pin 1 on the sonar board will end up on pin one on the motor controller. Theory is a nice mental experiment but a buzz check is ‘reality’ and important when extreme currents are possible.