Help repair a blown infineon 36-72v 12 fet grin controller

[electr0n]

My controller was consistently overheating in a bag and began cutting out intermittently. So I opened it up and found a loose component TL783C. I also spotted a burnt resistor beside it. So I attempted to solder the transistor back on and replace the resistor with the big 5 watt one I had on hand, I think it was pretty close in value to the original but I can't recall exactly, it was a while ago. Upon testing it out I got a loud pop, capacitor blew up (seen in photo second from bottom beside the large cap) and some nasty smoke

I took some pictures so you can see what I'm talking about. If anyone could kindly walk me through repairing this I'd be eternally grateful. I'm not sure how to go about it and I'd love to be able to perform minor repairs on my controllers as I doubt it would be economical to ship it out to somebody to have it done for me.

 

[DAND214]

Is the transistor you replaced facing the correct direction?

Dan

 

[d8veh]

The TL783C is the 12V (14V) regulator, not a transistor. Capacitors blow because they got too high a voltage or reverse voltage. I'm looking at the repairs you've done so far. It looks like you've destroyed the pads where the regulator is soldered. Are you sure the legs are connected to the traces on the PCB? The next problem is that you didn't trim the legs on the resistor. They carry full battery voltage, so if they touched any other pad boom! My guess is that the capacitor that's blown is on the 12V line. Somehow it's got battery voltage. Did you put the PCB down on something that shorted it somehow? I'm wondering if you've now damaged your FETS if they got battery voltage on the gate. It might be time to start looking for a new controller.

To test the regulator. When the controller's connected to the battery and switched on, you should have battery voltage on the right leg (viewed from front of the regulator) and 12 -18v on the middle leg. If you've got battery voltage or higher than 20V on the middle leg, that's why the capacitor blew.

 

[electr0n]

I think you're right about me damaging the traces on the board where the regulator connects. Looking at it now it appears one of the legs was not connected properly. So probably that capacitor did receive the full pack voltage and popped.

I did this last summer so it's been a while but I'm pretty sure when I was testing this I had the board pulled out of the case enough that the resistor legs didn't short to anything. The resistor seems to be attached fine so I'm guessing the failure point was likely the regulator and I'm pretty sure it's facing the right direction.

Anyone know the value of that blown capacitor? I guess the most straight forward thing to do is replace the capacitor and probably also the voltage regulator, or at least get it soldered on there properly, and give it another try. By the way when I'm testing the regulator would I be touching the negative lead on the meter to the battery negative and the positive on the legs mentioned?