Jrk not responding to tll rx signals

I have been using two Jrk21v3s for a differential steering robot.
After a few weeks of use, one jrk began indicating a loss of power
with the flickering yellow light. Eventually the Jrk did not respond
to ttl rx signals. The malfunctioning JRK does respond to motor commands
from the JRK software utility program and does not indicate any errors.
I am using an arduino to send the serial commands to the Jrks.

With the exact set up, the other JRK works fine. I also made sure to
set the correct device ID when trouble shooting. I also made sure that
the connections are properly grounded.

After a hard reset, the JRK still is unresponsive to the rx signals.
After several hours of trying to get this fixed, I have concluded that
this is a hardware problem and need a to get a replacement.

However before placing an order for a new JRK, I wanted to make
sure I was not overlooking something.

Thanks for your help or advice.

Everything you described sounds good, but you didn’t mention exactly how everything is connected, including the Arduino, both jrks, your power supply, and the motors. A photograph of the electronics and a wiring diagram would help us see if there’s anything wrong.

You might also want to simplify your Arduino code down to just a few lines which send out a few simple commands using the Compact protocol (so the device id on the jrk doesn’t matter). If you have a very simple Arduino program and it doesn’t work, you could post it here and I’ll see if I notice anything wrong.

When you tested the other jrk and found that it worked in the exact same set up, did you make sure that both jrks had the exact same configuration? (You can use the Save/Open configuration file feature of the Jrk Configuration Utility to easily do that.)

Also, what do you mean by “hard reset”? The jrk’s reset line should be sufficient for resetting the device, but you should also try powering it off. To do this you would have to disconnect everything in your system from all power sources: this includes USB and batteries. (The jrk can inadvertently be powered through the Arduino’s TX line if you don’t power down the Arduino.)