RE: DX 7 troubles
Let me first establish whether you're binding or linking.
I appologize in advance if any of this is old had but its your first post and I have no way to gauge your experience level.
Binding is the process of using the bind plug (rx) and bind button (tx) to pair them. After that you remove the bind plug.
Now when you power up the system you're linking a system that you previously bound. Seems you know about model match so we won't get into that.
Another thing you may or may not know is that you should be a couple of feet away when you're linking, and if you're having trouble make sure to step away from metal shelving, metal table tops, and or pickup truck beds or the like.
If after that you're still having issues, remove all servos and see if the system links up with solid lights. Then power down both and add servos one at a time and see if you have a servo or something shorted.
While troubleshooting remove anything from the reciever end but a battery and servos. No extensions, switches, or speed controllers and make sure the reciever battery is fully charged.