AX3550 Comm Problem

We have been using the AX3550 in RS232 mode for some time now and it has worked fine. Today, the 15pin to 9pin cable melted out (we think due to a floating ground problem) and the controller will no longer recieve serial commands, although it will send them such as its version info on startup and watchdog signals. Would anyone be able to give us a schematic on the RS232 components of the board? Do the two 4N25 chips have anything to do with serial communication? If not, what chips are related to RS232 that could be sensitive to burning out?

Thank you!

Cable melting will happen if the controller's thick ground wires are disconnected from the batterywhile the red wires are conntect. When operating the motors, high current will then find its way to the battery's ground via the RS232 cable.

As far as damage to the RS232 input circuit, this is aways a possibility but the circtuit is quite robust and should have survived such a problem. You may see the schematic of that part at <A href="dev.roboteq.com/dev1/files/drawings/ax3500v20-RCinput.gif" target=_blank>www.roboteq.com/files/drawings/ax3500v20-RCinput.gif in case you want to toubleshoot.

>dev.roboteq.com/dev1/files/drawings/ax3500v20-RCinput.gif

I can\'t seem to find this file. I have an ax2550 with a comm problem. It accepts commands but does not send anything back to my PC. I\'d prefer not to send the unit back for what seems to be a simple repair