We have no robot light when powered on. The vex net and game are flashing yellow.

Please keep posts about the same problem in the same forum thread. This will help keep track of the problem and solution.

I need lots more detail before I can begin to offer more suggestions. Please describe the entire sequence that you have followed, and the results of everything that you've tried. Since I can't physically see your robot and what you've tried, it's important that you share as much as possible.

I have reset the cortex and the remote control. Reloaded firmware, master cpu, rebotc firmware downloaded and controller downloaded again, several times. Switched batteries including trying the high school one that worked on their robot. During the firmware download we have a red robot light. When I disconnect the AA cable and power up the robot we have no robot light. Vex net and game light are blinking yellow. The joystick light is green.The robot light on the controller is also out, no color.

What version of ROBOTC are you using?

Are you able to download a program to your robot?

Have you synced the VEXnet joystick with the Cortex, by connecting them using the USB A-to-A cable? http://www.education.rec.ri.cmu.edu/pro ... _guide.pdf

2.31 RobotC
We had it working up until last night. We had been downloading programs, but now can't.

vex cortex and joystick are synced. When we go to download firmware the red robot light and green vexnet and gamelight

Anytime we connect the USB A to A we have a red robot light. Have put new batteries and when disconnect usb cable and turn robot on, get no robot light.

WE have it working right now. We think it was a bad USB A to A cord. We borrowed one. Thanks!!!

Glad to hear it's working!

We are having the same issue mjack was. We have downloaded the sample program, reversed the polarity of a motor, and ran into battery-life problems(I think that is when the ROBOT light and/or JOYSTICK light is red). Now, we can't get the remote control and cortex to establish a link.

After connecting the usb a to a, the ROBOT light and VEXnet light on the cortex blink green as they should, but when the USB keys are inserted and the remote and cortex are powered on, the vexnet light on the remote blinks red and the ROBOT light on the cortex is out and the vexnet and game lights are blinking orange/yellow.

tried replacing the USB a to a. still no link.

Have you tried different VEXnet Keys? It's possible that you may have a bad VEXnet key.