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Let's take a look at the sine wave you would see if you hooked up an oscilloscope to a typical household power supply. This is showing reading line with respect to neutral.
Hopefully you're already familiar with using a sine wave to represent AC voltage like this. To define a little terminology: the peak voltage (shown in green) is the voltage difference between the middle line (0 VAC) and the highest point of each peak. This diagram shows 170 VAC peak. Peak to peak voltage, on the ot
The general rule for dryer vent airflow is that, if the airflow feels like a breath (even a strong one), then you have a problem. This rule of thumb will serve you well a lot of the time, but sometimes a "calibrated palm" just isn't enough. Sometimes, you need to get an actual measurement of the airflow so that you can compare it to the specifications.
What you really want to know is the volumetric flow rate of the dryer exhaust. That is, how much air it's pushing out over a particular peri
We’ve all been hearing about R600a refrigerant for years now, and the reality is that it’s no longer an innovation in the area of household refrigeration; it’s the new standard.
With the majority of new refrigerators now being R600a models, repair companies need to be ready to perform sealed system repairs on them. This raises a few questions for these companies: how is R600a different from R134a, and what do I need to service R600a refrigerators?
R600a (let's just call it R600 from he
Ghost voltage is a term that you'll hear used in tech circles, and often incorrectly. Ghost voltage is the name of a very specific phenomenon, but I've seen it used variously to refer to failing under load, high resistance connections, and even simple open circuits. What does it really mean?
What we call ghost voltage is transient, seemingly sourceless voltage. It does, of course, have a source. You know how when current flows through a conductor, it produces a magnetic field? Well that mag
We're going to take a dive into what exactly is going on electrically with the high-voltage circuit in a microwave. We'll use this specific schematic as an example, but these principles apply generally.
Don't worry about most of the schematic. All that matters to us right now is the high-voltage section -- the transformer on the right side of the schematic and everything to its right.
If you're not familiar with how magnetrons work (or even what they are), then this circuit
Here's a puzzling scenario on a Samsung refrigerator: the ice dispenser door keeps opening and closing nonstop.
When you encounter a weird problem like this, it's easy to lose your head and just start throwing parts at the machine and hoping one of them will fix it. But it's always important to keep our fundamental troubleshooting principles firmly in mind. In this particular case, troubleshooting is made even more difficult by Samsung providing us with a very low-resolution schematic -- bu
BLDC motors aren't new technology in appliances anymore -- in fact, they've become the norm. As such, it's important to be aware of the different configurations you'll see these motors in across appliances. These configurations fall into three categories: 2-wire, 3-wire, and 4-wire.
An important thing to note before we continue: all BLDC motors in appliances are run by inverters. The inverter may be a separate board, like you'll see in washers with BLDC motors, or it may be built into the m
Thermistors are everywhere in appliances these days, and they're a relatively common-fail item, so wouldn't it be nice to stock a supply of them in your service vehicle to be used on any occasion?
Well, in order to determine how feasible that is, we need to answer a question: are all thermistors interchangeable?
The short answer is no. The long answer is that thermistors are not interchangeable brand-to-brand, but they can be interchangeable within the same brand, depending on the manu
If you read my previous post about sealed system basics, you know that understanding the thermodynamic states of refrigerants (saturated, subcooled, and superheated) is essential to sealed system troubleshooting. In that post, I explained these states in terms of a simple pressure-temperature table. While that keeps things simple, it doesn't really give you a strong visual and mental model for how the refrigeration cycle works thermodynamically.
That's why we're going to spend this whole po
Sealed system thermodynamics is a deep well, but fortunately, you only need to skim the surface to gain a functional understanding. And as techs, it's this functional understanding that we need to acquire in order to effectively troubleshoot.
To do that, we're going to cover the three central concepts to understanding a sealed system: saturation, subcooling, and superheat. Let's start with the one upon which the other two hinge: saturation.
In order to talk about what saturation is, we
Let's crack out our schematic-reading skills and take a look at a seemingly straightforward washer lid lock circuit.
Notice that, while they give us labels for the pins, that's basically all we've got as far as specs or info about the control board's algorithm. So if we want to figure out how this circuit works during operation, we'll have to crack out some Circuit Fu™. That means using both our understanding of electricity and our understanding of the intended function of a lid lock
Why is it that manufacturers (such as GE, Electrolux, and others) always recommend that you seal any splices you make in their refrigeration units with silicone grease? The simple answer is that it keeps out water. This is obviously desirable because water can both corrode and short out electrical connections. A splice is already a weak point in a circuit, so especially in wet environments, you want to give them as much lasting power as possible.
And it gets even more interesting when you'r
Ohm's law, meaning the set of simple equations that define the relationship between voltage, current, resistance, and power, is an essential tool for appliance techs. Not only is it the cornerstone of understanding electricity, but it's also an invaluable troubleshooting tool. This said, there are some loads to which the simple form of Ohm's law doesn't apply. The simple form of Ohm's Law only takes into account real resistance (ohms) but does not consider other ways that electron movement can b
@fillthebarman ran into an interesting problem the other day: he had a stacked washer and dryer where the washer could only be run when the dryer was running. How is this possible? Brother @sh2sh2 had the answer:
A brilliant piece of insight, and precisely what turned out to be going on here. But how does this happen, exactly? Let's look at the schematics. Here's the washer:
As you can see from the circled bit, the power supply for the washer comes right from the dryer's connec
Some techs long for the "good old days" of mechanical controls, when troubleshooting appliances was supposedly simpler. But the universal use of electronic controls nowadays actually provides many troubleshooting benefits -- in particular in the form of error codes and diagnostic modes.
The purpose of error codes is for the control to tell you its best guess of what's wrong, based on the algorithms programmed into it by the engineers. Note that the engineers' best guess is sometimes a very
To follow along with this blog post, you should go ahead and download the refrigerant slider app called "Ref Tools" to your smartphone (don't worry, it's free!). It's the one developed by Danfoss. I'm going to be referencing a few features of that app as I explain some properties of refrigerant, so go ahead and familiarize yourself with it. It's a great tool to have on hand regardless, since it lets you painlessly calculate superheat and subcooling in sealed systems.
Got it? Good. What I wa
Put simply, diodes are devices that only allow current to flow in one direction. In DC circuits, this means that a diode can either act as a conductor, just as a stretch of wire would, or as an open in the circuit, depending on the configuration. See the examples of DC circuits with diodes below:
That arrowhead-like symbol is the diode. The fat end of the arrow is the positively charged anode, while the narrow end that meets the straight line is the negatively charged cathode.
Fi
If you're getting into appliance repair, or even just looking to downsize an overstuffed tool bag, you might be wondering: what are the absolute essentials that you should bring with you on any service call? Well, having my fair share of experience in the field, I'll put forward Team Samurai's list of must-have appliance repair tools. Note that this isn't supposed to be a totally comprehensive list -- just the bare essentials.
Multimeter with a loading/LoZ function
If there's a t
One of the Appliantology Brethrens presented a small head-scratcher for us the other day about a GE GTWN4250D1WS top-load washer:
Sounds like a real problem, doesn't it? Back in the good ol' days, when you set a top-loader on maximum fill, it would fill that sucker all the way up. But wait -- before you start tearing things apart to take a look at the pressure sensor, let's listen to some words of wisdom from Brother @sh2sh2:
Ahh, well now, looks like we were about to get tricked!
Here at Appliantology, our primary mission is to support appliance repair techs in performing prediagnosis: the method of performing as much troubleshooting as you possibly can before setting foot in the customer’s home. Prediagnosis is the biggest factor in increasing FCC (First Call Complete) rates, and the higher the FCC rate, the higher your company's profitability.
So how exactly does one prediagnose, and how does Appliantology help with that? Well, let's walk through the journey of an
You're probably familiar with the term "split-phase motor", but do you actually know what it means? That's exactly what we'll dive into in this post.
The whole trick with motors on single-phase, standard household power is how to get them going from a dead stop. Once the rotor is spinning, it'll keep going happily as long as power is applied to the motor winding. But without a little engineering, single-phase power won't get a motor spinning -- it'll just hum and twitch in place.
The t
Here's your scenario: you're working on a Whirlpool CAM2742TQ2 Washer, and you've determined that the auto temp control (ATC) has failed such that it won't energize the water valves and allow the machine to fill. You intend to replace the ATC, but it's on backorder. Is there any clever trick you can think of that will at least get the customer going temporarily while they wait?
Time to crack out the schematic.
It looks like there's a lot going on here, what with all those alphabe
Many techs are intimidated when it comes to troubleshooting control boards. After all, we're talking about computers here -- computers that just so happen to run appliances. But as complicated as that may sound, control board troubleshooting really boils down to just three things: measuring your inputs, measuring your outputs, and understanding the board's algorithm.
Let's start with inputs. Input just means anything, be it a power supply or some information, that the board receives f
By now, most of us are used to variable speed drive motor systems in appliances. The control board sends a PWM signal to an inverter, which tells the inverter how fast to run the BLDC motor.
While this is the type of inverter that's been used in appliances for years now, it's not the only kind of inverter out there. In fact, another type of inverter is starting to crop up in the appliance world, and it may very well become the norm for some applications. It's called a drop-in inverter, and
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