OK, i have investigated a little further this morning. I disconnected the motor wires from the decoder and powered the motor with a laboratory power supply. I set volts to around 5 and current clip to 500 mAh then connected the motor. Immediate current clip, the motor is toast.

I have four Bachmann Econami Soundvalue SD9s. Some time ago while consisting three of them one stuttered a couple of times and then started tripping my short detector when starting to move. Today, two more of them have gone the same way. All sound functions work perfectly and everything is normal until throttle is applied. At this point the locos will move a little and then either reset or trip the short detector. My command station is DCC-ex using the arduino motor board so i should be good for at least 1.3 amps, I have seen values on my amp meter in excess of this when the effected Sd9s are tripping the detector. When the decoder appears to reset i suspect that the internal current monitor is being tripped. All three effected decoders where in a consist with other SD9s when they started exhibiting the symptoms described. I have reset all CVs by programming a value of 8 into register 8 and then cycling the power as described in the manual. This did reset everything but doesn't solve the problem. Has anyone else had a similar problem and have you managed to fix it?