TReX Jr. stuck in safe-start mode

My TRex Jr. is stuck in safe-start mode after a couple (2-3) hours of operation. I have successfully gone through the self calibration several times with 2 separate receivers. I am useing only using two channels and the LED sequence after the calibration is green-green-red-red-red. This sequence properly is shown at board power up and is then followed by the green LED rapidly flashing.

I have tested both of the receivers with servos and a pico switch which all worked fine. This along with the successful calibrations prove that the receivers are working properly.

I read the manual and all it says about the this current state is that the board is waiting for a valid input on channel 1 for R/C mode which should be met because a valid R/C signal is sensed during calibration.

I am running a tamiya dual gear box and powering the board with a 11v supply (8 AA’s). I am powering the receiver with a separate 6v supply (4 AA’s). The BEC jumper is DISABLED. All the batteries were charged and reinstalled with no joy.

While the system was working the other two channels of the receiver (which where not connected to the TReX Jr.) were acting erratic when the motors would run. The pico switch was rapidly switching on and off and the servo was randomly moving back and forth. I have not had this problem be for with these receivers which have both been used in an R/C airplane which uses a 15amp ESC/BEC without problems.

I am currently trying to find my usb-serial adapter so I can make a serial connection to get more data. What do I need to look for other than the dead-band setting?

My main concern is getting past this safe mode. But I’d also like any suggestions on what may be causing feedback/interference to the receiver. Does the board draw power from the signal inputs when the BEC jumper is disabled? Would an isolation/booster circuit eliminate this without interfering with the TReX?


I made up a serial interface cable today and have been trying to connect with the configuration software but I keep getting the " cannot find a connected TReX motor controller" error message. To check my connection I attempted a firmware flash and it completed successfully… And that got me out of the safe start mode, YAY! I am still trying to get the software to connect so I can start tweaking some setting (my motors are a hair over the 2.5A rating at stall and occasionally cause an overload state). I read the other post about serial connection issues which is the same problem I am having at the moment but there are no answers there. So I am still researching and experimenting with my fingers crossed hoping I don’t fry my board before I get a connection.

Edit - I think that the problem may be my USB/Serial adapter (too low of voltage for RS-232 and invalid format for TTL). I will attempt a connection on the desktop later.

Edit - No joy when connected to the desktop. I noticed that when data is entered in hyper terminal the green LED illuminates until the text is cleared, but it does not even flicker when a connection attempt is made with the configuration utility. I keep getting the error message “Could not detect a TReX motor controller on port 1.” It does not seem to be even trying. Going through uninstall and reinstalling the software hoping that I stumble across an answer.

Finally got the configuration software to talk. The problem was that I was following directions instead of what was implied, I guess… I needed to start up with the program jumper on, remove it with power on (the manual explicitly says NOT to do this!) and then attach the serial… basically the firmware flash directions, BUT without removing the mix jumper. So I was able to tweak my motor limits just a hair so that the system no longer stalls out.

The other channels on my receiver are still being affected though. When I get to about half speed the lights that are controlled by the pico switch on channel 4 begin to switch on and off about once per second, and the servo on channel 3 cycles up and down at about half that interval. I need recommendations on an isolation/booster circuit that I can build or buy that will help with this.