FET problems

[spamman]

Okay, so today I did my own fet mod using 4 IRLML2502CT-ND fet's that i purchased from digikey.com. Well, problems. Maybe somone can help me out. The steering works, but the car doesn't go forward or reverse. As far as i can tell i have all the jumpers connected properly, and all the fets properly soldered into place. Here are pics of both sides of the pcb:




Now i checked the voltage at the battery, it's good. I checked the voltage at the motor... weird stuff there. It shows 1.2-1.3 volts at either motor terminal when the car is still. When pressing either forward or reverse on the controller the voltage drops to 0v on both terminals. These measurements were done using the negative battery terminal as ground.

Anyone have any ideas?

[slider69]

i dunno if you can check the fets...
but be carefull... those look torched to me...any time that outer layer of plastic has melted, something has gotten too hot!..prolly in soldering...u only replaced 4 fets, right.... look at the one top left.....don't overheat when u solder.... i think u might have melted all of 'em(the ones u replaced), if nothing works at all. also, you might want to try another method....the one where you replace some of the fets with irlml6401s. i did that to my msizer pro and it was cool until i screwed up the charger and set it on fire...

[spamman]

Nah, turns out i had the fets on one side, upside down (you have to mount them upside down). The residue you see is left over flux junk. I would have used the 6401, but they are pointless unless you are doing a dual cell.

[slider69]

well...that's good to hear!! Bet the little fella rips now i might have to try the 4x 2502 mod...considering i got a few of those layin around.... just have to find a new car...