Lishui controller short circuit

[honya96]

I have 2 controllers with the same problem, overheating and turning off even with light load they are the same model number: LSW772-159F they have STM32FEB KC6T6 procesor, I narrowed the problem down to 5v line, after connecting limited current the processor boots and starts heating, interesting is that it heats even after disconnecting all 3 VDD and VDDa lines, so it only has ground.

It's. 1.8Ohm from 2 of the VDD pins to ground, the third is 5K and VDDa also about that. But I don't get it how it can heat with them all disconnected.

Any ideas?

 

[fechter]

Is it the microprocessor that's heating or the whole unit? Sounds like the processors are fried or there is something shorted on the board.

 

[honya96]

Is it the microprocessor that's heating or the whole unit? Sounds like the processors are fried or there is something shorted on the board.

Hello, thank you for your opinion, only the procesor is heating when 5v applied.

When it's turned on on 36v battery, the lm317 and the big resistor is heating. When it's not connected to battery, just 12v on the output of lm317, then the 5v regulator is heating, and when I connect 5v on the output of the regulator then the procesor is heating, that's how I narrowed it down.

Weird thing is that it's heating even when all positive inputs to STM32 are disconnected, there's nothing on the other side of PCB, and it's clearly the processor that's getting hot

And also, it starts heating after boot, not right after the voltage is applied, I believe. There is a delay in voltage drop.

I think I have one spare processor so I may "try" to change it tomorrow, but I expected some shorted cap, not the STM to be bad.

 

[honya96]

So the one I have spare is F103 C8T6 so it probably won't work.. if you wonder how I can change it, I have EBICS firmware flashed, from stancecoke, so that would probably work on a fresh processor too..

 

[honya96]

I just got third controller with the same problem, so definitely common.