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June 27, 2020
Why I Was Almost Shocked – in Two Ways – by a Small Home AC Appliance

Why I Was Almost Shocked – in Two Ways – by a Small Home AC Appliance


It’s a legitimate complaint that many of today’s appliances are too complicated, difficult, or costly to repair — and that they get “bricked” (turn into useless junk) when they break — especially if they are more than a few years old. This may be due to lack of parts, poor physical access, or the cost and sheer difficulty of replacing a circuit board loaded with ICs and more. For some of these appliances, you’ve likely experienced the frustration of knowing that if you could just get into the unit and see what was going on, you might be able to fix it. In many cases, we are legally warned off by the label saying “No User Serviceable Parts Inside.”

However, that frustration is not always the case. My basic, low-end, totally non-electronic Black & Decker Toaster oven suddenly died — the little red light that shows it is on stayed dark, as did the heating elements. As the most common failure mode for this type of unit is a slow decline — as those elements darken over time, not something you can fix economically or safely — I thought the problem here might instead be a loose connection or bad switch, Figure 1. (Of course, I checked the outlet and power cord first, to make sure those weren’t the problem.)

Why I Was Almost Shocked – in Two Ways – by a Small Home AC Appliance
This Black & Decker toaster oven is the epitome of simplicity: no electronics, no software, no internal power supply; just two user-set electromechanical controls and a red “power-on” light. (Image source: P.C. Richard & Son)

Since the unit went totally and suddenly dead, I thought “hey, I’ll take a look at fixing it.” I normally hesitate to poke around inside appliances that uses the line AC directly throughout, as there is no AC/AC or AC/DC low-voltage safe zone and you have to be sure to put it back together just right. I checked the Internet for any repair insights on this unit and there were some sites and suggestions (see references). Though they weren’t directly applicable, they nonetheless gave me the mental momentum I needed.

That led to shock #1: Taking the unit apart was delightfully easy. There were no hidden screws, glued or sonically welded plastic seams, snap-together tabs that break when you pry them open, or anything to impede opening it. There were just 10 small, fully visible screws. In a couple of minutes, I had the protective shell off and separated from the control switches and toasting area.

Inside, the unit is wonderfully simple. There are just two controls, and both are hardware in the traditional electromechanical sense of the word. One knob sets the desired baking temperature or broil mode; the other is a user-set, spring-wound rotary timer.

That’s when I had shock #2. While the wires are covered in some sort of woven insulation, which I assume was some sort of heat-resistant material, their connections on the timer and thermostat were fully exposed AC-line points. I was able to see immediately was that one of the slide-on connectors to the thermostat had slipped off and was just hanging out there in the middle of nowhere, Figure 2. I assume it came off because it had not been pushed on all the way, or due to vibration from years of slamming the glass door, or both.

Why I Was Almost Shocked – in Two Ways – by a Small Home AC Appliance
The electrical-control area of the toaster oven, on its right side: note the free-floating live wire and its slip-on connector (in the circle) that has come off from its tab on the corresponding upper front-panel control, and which could have instead touched the oven’s metal shell. (Image source: author)

But, the bigger aspect of shock #2 was realizing that I had not used a proper three-wire grounded plug and outlet, but instead had an ungrounded AC line. If the live connect that was now free had instead touched the unit’s metal shell when it popped off, the metal case would have been live at AC-line potential. While that is a “double-fault” event, it is certainly a reasonably plausible one. Unlike plastic-body line-operated power tools with two AC connection (hot and neutral, no ground), these toaster ovens are not double insulated.

In the end, I crimped the slip-on connector slightly and put it back all the way on the connector tab, and everything worked fine. Reassembly was also trivial. I was pleased at being able to diagnose and easily fix that dead appliance in just a few minutes, which doesn’t happen often these days. I was also reminded that bad stuff can happen, and AC-line ground is there for a reason that precedes its use as a designation for a signal common or low-voltage, ungrounded, power-return path. We now use the term “ground” in electronics so often and so casually that we can forget its primary meaning and critical function.

What has been your experience fixing — or trying to fix — appliances and even gadgets ranging from simple to complicated? What did you find to be the biggest problem: documentation, getting into the unit, diagnosing the problem, or making the fix, or getting everything back together safe and like it was? Have you ever had an extremely simple fix, such as a loose wire, once you got in there?

Meanwhile, I will go check all my new and old three-wire outlets for their ground integrity using a simple yet effective $5 outlet tester, Figure 3.

Why I Was Almost Shocked – in Two Ways – by a Small Home AC Appliance
An inexpensive AC-outlet tester such as this one is truly “plug and play”: plug it in, look at the LED pattern, and the outlet wiring status is made clear. (Image source: Klein Tools)

 

References

  1. Ifixit, “Toaster Oven Repair
  2. Ifixit, “Black & Decker Toast R Oven TRO200 Repair
  3. Ifixit, “Most helpful Black and Decker Toast R Oven questions
  4. How Stuff Works, “How to Repair a Toaster Oven
  5. ManualsLib, “Troubleshooting – Black & Decker TRO4075B Manual

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