My Milwaukee 0224-1 Magnum 3/8" 0-1,200rpm Hole Shooter was purchased new in April 1988. It has been a strong / reliable homeowner's tool for over three decades.
A recent home project included tiling 3,000 square feet of flooring. This drill was used w/ an auger to mix dozens of bags of mortar. That extraordinary "continuous" extended load burned up the variable speed part of the drill.
Fortunately the drill was still operational. It failed to operate as a variable speed, but continued to operate in full speed mode.
In this early generation drill, the speed controller part is embedded within the currently discontinued / obsolete 23-66-1350 trigger switch assembly. An image of the original switch shows bubbled up plastic heat damage, where that internal speed controller part is located, within the trigger switch. That obsolete part was located then installed, now normal operation has been restored.
The assembly drawing / BOM for this early drill was located. That document number is: Bulletin No. 54-06-0227. I was unable to locate the Wiring Diagram for this early drill. That document number is: Wiring Instructions 58-01-0072. The only wiring instructions I found were for the slightly newer drill, using the separate 14-20-0245 speed controller part, not appropriate for my drill. To that end, I took lots of photographs during disassembly to ensure I could replicate the wire placement / routing during reassembly.
The only difficulties for this repair was the removal / replacement of the poke-in switch wires. The ends of these stranded wires are soldered, to maintain the strands as a solid cluster. This early-generation switch doesn't have a secondary hole for releasing the wire retention tang.
The wire removal from the old failed switch was easy enough, a light constant pull force while partially rotating the wires back and forth on an arc.
The wire installation into the new switch didn't initially go smoothly. The wires are not stiff enough to overcome the wire retention tang, making it impossible to force the wires into position. A slender jeweler's screwdriver was used to open the wire retention tang. While open, the wire was forced into position, then the screwdriver was removed, leaving the wire retained by the tang.