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\usepackage{caption,graphicx}
\date{2018 (revised 2019)}
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\section{Harbor Freight Bauer Drill Repair}

\subsection{Overview}
At a company I work for a drill was purchased from Harbor Freight. It was a Bauer 1791c-b1 drill. Sold for about \$40 US in 2018. I knew buying anything electrical or electronic was a bad idea from Harbor Freight. It is generally known that while their products are cheap, they are also likely to fail early, and fail often (to steal a word from startup world).

\subsection{Background}
I was using the drill when it failed. Not in any excessive capacity, instead simply using the drill, moderately. I began to smell something burning, but the drill continued to work. After another moment, the drill was completely failed. What had happened, is that one of the DPak FETs had failed, then the other. 

\includegraphics[scale=0.3]{../pics/DSCN0677.JPG}
\captionof{figure}{This style seems to be the current favorite (techy red and grip, with a square lithium pack). A trip to the hardware store will reveal other brands with similar looks as of 2018.}

\subsection{Repair Notes}
2 Dpak components have big burnt out holes on them. Need replacement.  What is their pinout?

Motor is Mabuchi model:  RZ-735VA-A014. Range 6-20 volts.
Switch before motor is 7.2 – 24 volts.

Micro is TI msp430g252. \footnote{Wait, this drill needs a microcontroller? As in a computer in a drill? Why not an IOT drill then? But, I suppose having an IOT drill is ridiculous, and likewise so is having source code in a drill.}
Question is, what is the level of the voltage regulator? Is it 20V?
It appears to be an onsemi model such as: CS52015
I can't find an exact match from Digikey which only searches current models, not historical models.

I may be able to throw an adjustable vreg with similar pinout in...
The battery is 20V. The dpaks are getting power, only when switch is pressed.

\includegraphics[scale=1]{../pics/mcupinout.png}
\captionof{figure}{Pinout for MSP430}


\includegraphics[scale=0.9]{../pics/schem.jpg}
\captionof{figure}{Rough schematic for board (see colour picture in repo). When switch is pressed, there is 20V on the tab of FET. I believe the FET must've overheated and shorted (perhaps counterfeit?). Though Right pin is to GND. Maybe it's a current limiter, not a FET, allowing Tab when V+ to be dropped down and current will flow. Too bad I wasn't able to stop using the drill before both FETs failed. I could've read one of them.}

\includegraphics[scale=0.7]{../pics/threadcapture.jpg}
\captionof{figure}{A short post to an anonymous image board for assistance}

\subsection{Work Log 12/2018}
I was unable to find the exact pinout for the N-Channel I needed, so thought maybe the anon was wrong in his post. I purchased some N-Channels which seem to be standardized with the pinouts being drain on the tab, not source. But these do not work. Short circuit protection appears to kick in, and the Dpak overheats quickly. I did not see any Nchannel Dpaks with the pinout he mentioned. Whether N channel or P channel or high or low side switching I see there are four types, with one being more common, and one being least common. (N Channel  - low most common. P channel low least common.). Upon further research, looks like anon was mistaken in pin names, but this link:https://www.embeddedrelated.com/showarticle/98.php
seems to show the drain as tab, and source as right pin would be correct here. So after the replacement, the devices spins for a short second, then stops. Something else is broken.

Checking the pins of the msp430 with a scope, I can see it has a sleep mode, a pin to control gate, a pin to control LED. I thought I saw UART, but it's just a CLK input. Led is two or three to the left. There also seems to be some pin, maybe adc monitoring drill (top, right side pin).



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