UMO won't stop heating hot end reaching desired temp.

[suncheez 0]

Good day.

Today I've changed the original head to e3d v6. I've connected the radiator cooling fan to the second fan connector at the mainboard and it spinning well.

Occasionally I've short-circuited the fan that cooling the plastic and BD679 transistor is gone for good, so the fan is spinning now at maximum speed all the time.

But there are two symptoms that I can't get:

1. Leaving UMO just powered on for a minute resulting switching it off (fan goes down, but the UController backlight is on) and then trying to power on without success.

2. I'm setting the nozzle temp to any grade and then heater starts, UMO shows the temp is rising, but it passes the limit and goes up until I powering it off manually.

I'm wondering what may I did burn out except the BD679?