help repair Scorpion SC-6989 12v cordless impact driver

[flat-earther]

Hi I got this Scorpion High Quality Products model SC-6989 12v impact driver and the problem is it only runs on full speed and LED light doesn't light up.
I got the tool with two dead batteries and I already using the good 18650 cells from the two made one working battery.
Initially when I got it I once hooked up a good 12v battery to it and it powered up and LED worked but now depressing the trigger only makes it run on full speed or nothing so there's no variable speed, but to be honest I'm not sure if this tool has a variable speed trigger. Also LED doesn't light up anymore.

On the PCB I measured 0.3ohm on a component that I circled in red in my photograph, is that a capacitor? Does that reading mean something? It doesn't have markings on it. The component was glued down and I bent it up.

[lotas]

Re: help repair Scorpion SC-6989 12v cordless impact driver

L1 is a choke (inductor), and it should show on the multimeter.

[stj]

Re: help repair Scorpion SC-6989 12v cordless impact driver

see if the mosfet LR8726 is shorted.
and test the led with your meter in diode-mode

[flat-earther]

Re: help repair Scorpion SC-6989 12v cordless impact driver

thanks for your replies.
I tested the mosfet LR8726 with one multimeter lead on the larger left metal part of it and the other alternately on each of the 3 smaller pins on it's other side, see photos where first measurement reads 0.3ohm, second 0ohm, third 84.8ohm. What do the measurements mean?
I tested the LED in diode mode and it reads 1.453 and reversing leads gives no reading. What do the measurements mean?

[stj]

Re: help repair Scorpion SC-6989 12v cordless impact driver

the diode test meters low, but the test usually makes it light up.

the mosfet is shorted - probably.
you need to remove it and test again.
the tab is connected to the middle pin - thats why you got 0 ohms, but the outer pair shouldnt look like that!

[flat-earther]

Thanks stj,
The LR8726 mosfet was the problem indeed, I wasn't ready to remove it before since I only had a soldering iron but now I have hot tweezers so I removed it and soldered a new one and now the LED lights up and the variable speed trigger works.
I also resoldered the 3 thin black, blue and red wires that go from the trigger to the control board since the wires fatigue snapped from the control board from bending them.
The LED and trigger behavior wasn't reliable though so I opened the trigger to clean the sliding contact which didn't help then I opened it further and saw the rocking switch contacts looked worn so I ground them clean with a small rubber abrasive bit, also accidentally bent the sliding switch copper contacts a bit but I think it's better since now it applies more pressure on the board it slides on (that actually may have been what was needed since when I moved the 3 thin black, blue and red wires right near the switch, the LED flickered on and off), after that it's all working properly now.