Repair your Makita Battery Charger

I picked up this Makita 1410 battery charger at a garage sale.  It was promised to be broken, and it was!  I hoped it was going to be the little fuse that you see at the upper right - if something falls into the receptacle and shorts things out or there's a big voltage surge, then that can blow.  BUT NO! fuse was just fine.
1411 charger is similar.

When I tried to use it, it would never complete charging the batteries.  Even worse, it would DISCHARGE the batteries while it said it was charging them.

I've found that WHEN THINGS GO WRONG with electrical stuff, it is almost always the three pin power component mounted to a heatsink.  Problem was that the battery charger had about FIVE of them.  One thing made it simpler though, four were encased in pookie which would have made them difficult to remove and impossible to identify!  There was one though, the first one coming in from the right here (near the AC cord)  was identifiable as a C4161 and wasn't pookied over.

I looked at the place in the circuit.  and it seemed to be controlling that transformer in the center of the card.  Well, that MIGHT be why the charger doesn't work. When I looked up the description of the part it called it a fast switch.

Removed the screw and desoldered the component.  Found one of the replacements for the C4161 was the NTE2337 (I used the NTE number because they have them hanging on pegs at my local Fry's)  The price was a little under $5 - I took a chance on fixing my charger rather than playing the Lotto this week.

There's the new component set back in.  I used some heatsink pookie on the back of the component although the original was mounted dry.

I'll be DARNED!  IT WORKS!  Looks like I can save myself a $50 dollar bill.

Now get in there and fix yours!
I don't know what the 1411 or 1413 look like inside. Let me know if they're similar.