Craftsman 19 volt cordless drill switch

Thread Starter

tinkerman

Joined Jul 22, 2012
151
I apologize if this is not the right forum to post a question on a variable speed switch in a cordless 19 volt Craftsman 1/2 drill switch.

Have a drill which suddenly runs only on full speed. Opened and find a transistor??? that is shorted on all three terminals. The numbers are almost impossible to read but have what looks like SK063 V6 in one row. It's mounted on an aluminum heat sink formed around the switch assembly. I'm wondering if it's a MOSFET like this: IRZ44N?

Can anyone point me to a typical circuit used in these switch applications? Or advise if I'm on the correct path? Should I replace the defective transistor with one listed above?

The batteries on this drill are long gone and not worth replacing. So it's wired to an to an external 18 volt battery in a permanent application on a sewing machine.

TIA
 

MaxHeadRoom

Joined Jul 18, 2013
28,617
That should work, can you measure or scope the input to the present device to see if there is any control signal? Otherwise a 555 PWM should work.
Max.
 

Thread Starter

tinkerman

Joined Jul 22, 2012
151
Closer examination of the chip with powerful magnifier I see what looks like this number:

P75NS04Z

Other numbers which appear to be:

GK06D
CHN725

Google search lists P75NS04Z as MOSFET N channel 33 volt, 80 A. TO220 case. Hefty current but I guess a stalled 18 V, 1/2" drill would draw fair current.

Make sense to you? I have to do the scope thing yet.
 

Thread Starter

tinkerman

Joined Jul 22, 2012
151
That should work, can you measure or scope the input to the present device to see if there is any control signal? Otherwise a 555 PWM should work.
Max.
Yup get square pulses which change width as the trigger switch is depressed. So I'm guessing the internals are working fine.

Yeah!
 
Top