So we have been testing the robot and all of a sudden the jag smoked. After opening up the jag, the resistor the fried. We replaced the whole jag and with the motor hooked up only on the positive lead and we fried another jag. What could be the problem if nothing is grounded to the frame? WHY ARE WE BURNING JAGS?
The culprit in such cases is often aluminum or other conductive dust in the jaguar. It is nearly undetectable. The best advice would be to cover your jaguars before drilling near them.
correction, transistor not resistor.
That makes metallic dust seem like an even more likely catalyst in the release of the jaguars magic smoke. transistors are fragile devices that don’t generally tolerate any shorts.
Which version of the Jaguar are you using? I seem to remember the old grey ones not being designed to have the terminal screws removed, and removing them would create little bits of metal dust that would get into the Jag. We fried three rookie year, and I’m pretty sure it had something to do with this, seeing as how we were using ring terminals. If you’re using the black Jaguars, though, that shouldn’t be an issue
Transistors are not fragile devices if they were, we wouldn’t be running 40 amps across them. A short can cause any number of failures outside the actual transistor. Most likely damage to the package of the mosfet.
Glad I saw this we had this samething happen to us it, I agree with all above you have to make sure no metal shavings get into the jags also make sure the conectors are right and good. Prevention is the best method for this one.
Bobo,
The Jags and Victors are not protected from reverse voltage polarity. With no load you can kill a controller just by connecting it incorrectly. Since you did not name the component (Q4? IC 1") we don’t really have anything to point to as a possible problem.
Al
If conductive metal dust gets into the motor controllers of any type, it could cause the “shorts” between different points in the circuitry controlling the output MOSFETS. This would cause the controller to operate in a way it was never intended to resulting in damage. At work, our production staff blow out and vacuum the equipment they are assembling (large 3-phase motor controllers) before they are sent to be tested.
I saw another thread where people were reporting that pushing the robot, with the power turned off, will cause the motors to act as a generator and damage the controller.
Just another myth I am afraid. You can charge your battery this way though.
A good job for Freshmen 
Always thinking!
So we are using the black Jags with the part number MDL-BDC24. The parts that fried were Q4’s We have lost 4 out of 4. Every one that we have tested has had some short on a transistor. It is possible that the aluminum dust has caused all the problems.
Bob,
The chances of four Jags having a failed Q4 are staggering. How are you checking the FETs? They should show a high resistance from the gate to the other two leads. When measuring the other two leads, they should show some resistance in one direction and a lower resistance in the other. You should be using a multimeter set on the diode test range.
If you look at the schematic you will find that Q4 and Q5 are in parallel. Are you sure that C42 is not shorted?
We had 2 Q4’s go. on the other two, they just stopped putting out output to the cim. I will show the responses to the electrical mentor because i am more on the building side. BTW, thanks for all the help.