I have mo ides what you are talking about. Please explain if you will. My E20 DA tractor came with a thin metal shunt across which the power meter was connected to display current drawn by the motor! The big shunts up front which control field weakening have all been removed for the AllTrax. Thanks,
Um. Ok. Let's start from the top.First, the things in the front of the tractor are *not* shunts. They are resistors. Second the resistors in the front of the tractor are *not* related to field weakening. They are there to provide series resistance to the motor armature for speeds 1-3 (in an E20). When in use they probably drop 15 volts plus across them, which would blow an elec-trak ammeter apart.
The resistors that control the field are on card #3, in the tractor body itself, up on the top right side. 4 grey resistors and a MOV.
Third, the elec-trak meter is not calibrated to display motor amps. It's desined to be a small volt-meter, measuring the voltage across a 20 inch (I think) loop of wire between the batteries and the tractor. This wire has a very low resistance, and thus a low voltage drop. The meter is designed to measure this very small drop and show it as a deflection of the little pin.
Fourth: The little metal strip in the center of the tractor itself is the shunt for the motor field current detector on card #4. This shunt needs to generate 2 volts or so of voltage to turn on the transistor/fet combination on card 4 and drop field weakening to the armature. This voltage is a lot higher than the one across the 20 inches of wire that the ammeter is calibrated to handle.
So...... When you put the ammeter across that shunt, the voltage went too high and it blew the meter up. You should probably *not* be using that shunt with the Alltrax anyway.
Hope this helps. Chris