can you take good closeup pictures? maybe if you post up some macro pictures of the area around the cap that blew up or all the way across where the gate drivers are, we can see something too.
maybe the cap you added is not enuff, but if you heard 2 pops, it seems like there should be 2 to replace
if it were me, i would use the diode tester with the board unpowered, and test D to S, and S to D on each FET all the way across. should be able to reach the legs easily from underneath.
not sure how to test the gate driver, but you would expect that the gate on each FET would swing up and down as the hall sensors toggled the controller through each pole of the motor, or each 3rd pole. so with controller powered up and the wheel turning just a slight amount, you should see a voltage come and go on the gate lead.
maybe someone else has a better test.
i wanna thank richard too for sending me a link that helped me understand how the output drivers work.
you will see that there is one FET with the source lead attached to the solder blob where the phase wire comes out of the pcb. and on mine there are 2 other FETS with the drains attached to it also. the one FET is called the high side FET or flyback FET and it has the drain attached to Vcc or the battery positive, and the other 2 are called the low side FETs or driver FETs and the drains go out to the ground or battery negative through the shunt resistor, as i understand it.
the high side FET is turned on by the controller after the low side driver FETs turn off at the end of the PWM cycle when they sink the current from the motor, and the inductive current coming out of the motor at that point can swing back into the motor without causing severe voltage spikes in the low side or driver FETs and causing them to breakdown.
when the controller is driving the motor for the part of the PWM cycle where the drivers are turned on, the flyback or high side FET is turned off and all the current from the battery goes through the motor then through the driver FETs to battery negative, or ground.
and then regen happens when the controller processor knows enuff to keep the driver FETs turned off and turns on the high side flyback FET to allow the induced current from the motors rotation to flow back to the battery through the high side FETs.
i hope i got that right. also if you look at the controller pcb, you will see that the flyback or high side FET has a gate driver of its own and the low side or driver FETs have a gate driver of their own that they share through a gate driver resistor for each which keeps the gate from turning on too fast.
actually for the gate driver there are several transistors together with caps and resistors all surface mount devices so that the 5V logic signal from the processor can turn on the gate drivers, which run off the 12V buss so they can deliver more power, faster, and turn off faster, when delivering the turn on charge to the gate and sucking it off when the FET is turned off.
so there will be 3 surface mount transistors, one turns on the gate driver using the logic signal from the processor, so that charge is pumped into the gate, and when that logic transistor turns off, the other transistor is active because it is now turned on and it sucks the current out of the gate.
if you notice closely, there is a big surface mount diode between the high side flyback FET and the power supply, or voltage regulator on the other side of the pcb, along with that little electrolytic cap next to the phase wire, and some other little surface mount resistors which allow the high side gate drivers' power buss to be 'pumped up' in voltage above the source voltage of the high side FET, so that the gate driver can operate in its normal regime above the source voltage to turn the flyback FET on and off normally even though the gate voltage for the high side FET is above the battery voltage.
the low side or driver FETS don't need that help and the gate drivers can operate normally off the 12V buss because the drains are tied to ground, and so the source when the FET is turned on is just an IR drop across the FET, dependent on the drain to source resistance and the current flowing through it.
hopefully this will make it a little easier to see what they are doing, and let richard, along with a buncha smart honchos here comment on my little intro to driver signals and how the FETs are operated. really, please critique.
now if my eyes were 50 years younger, maybe i could see it. hehe. BOL, dm
Funny thing is, the bike would still run after the pops, it would just do it in a very odd way: it would "chug" along in a very jerky and loud manner with very little power.
