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
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
Why are microwaves so picky about the way they do their door switches? Are two different interlock switches really necessary? And what does the monitor switch even do, anyway? All these questions and more answered in this short instructional presentation.
Big props to Brother @Vance R for his explanation of these switches in this topic, which inspired us to make this video.
Topics covered include:
Schematic analysis of interlock switch circuits
Identifying if the schemat
In this video, we give a comprehensive answer to this question: "Why is it that high ambient temps cause high side and low side pressures to rise?"
This simple question about one specific sealed system problem scenario is a great opportunity to take a deeper dive into how sealed systems work, how they're affected by their environment, and how an issue in one area of a sealed system has ramifications for every other area.
Topics covered include:
The temperature/pressure relation
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
What do you do when even the service manual can't be trusted?
In this video, we discuss how to deal with bad or missing information in all kinds of tech docs -- service manuals, tech sheets, schematics, you name it. Topics covered include:
Pin numbering discrepancies
Reconciling pinouts with schematics
Identifying power supplies
Recognizing incoherent specs
What are dummy directions?
..and more!
You can watch this one right now for free! We've
We've got an interesting one for you today -- take a look at the "IDI Motor" in this schematic:
That's the ice dispenser auger motor in this fridge, and there are a couple interesting things to figure out about it. First, what's the deal with its power supply? If you look at the label on the motor, you'll notice that it says:
So that's a 120 VDC motor. How does that work?
A quick look through the documentation tells us that this motor is designed to run in two differen
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
Appliantology has always been a community built by techs, for techs, and one of the biggest ways the community grows is by simple word of mouth: techs telling other techs about all the awesome learning, discussions, and tomfoolery that goes on here.
To that end, we've got a great opportunity to show our appreciation and give a perk to techs who spread the good word of Appliantology. All site members, including Grasshoppers, can become Appliantology apostles. "Apostle" means "one sent out" u
Let's look at a seemingly simple load that has more going on than you would think: a multi-speed hood fan in a microwave. The questions we want to answer are: how many speeds does this fan have and how does it achieve those speeds?
If you look at the spec block for the motor, the answer to the first question seems easy -- looks like it's a simple two-speed motor.
But when you look elsewhere in the tech sheet, you find this voltage table that seems to state you have four speeds. (
Imagine you're in this situation: you're trying to do some ohms testing on the heater of an LG electric dryer. You're reading 21 ohms across a single coil, and 42 ohms through both coils. But when you look at the spec on the schematic, you're seeing almost exactly half that:
Weird. Maybe the heater is out of spec, but that's a weird discrepancy. And it's bizarre that we're reading double the specs given.
Can we get a second opinion? You look elsewhere in the manual, and you find
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
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
Unlike when we first started Appliantology, the Internet is now full of appliance repair support resources. From Facebook groups to subreddits to Voxer and Telegram groups, you've got your pick of the litter when it comes to what flavor you'd like.
Are there advantages to using a private forum-based site like Appliantology over the social media plantations? You betcha: Privacy and Functionality
Feeding Big Brother
All the Big Tech social media sites have one thing in common: they
Here's a scenario taken right from the trials and tribulations of an Appliantology tech: you're troubleshooting a no heat complaint on a GE electric dryer. You start your troubleshooting with the heating circuit, and your findings are puzzling: there are 120 volts on either side of the heater with respect to neutral, but when you do a voltage reading across the heater, you get some weird amount like 80 volts. What gives?
There are a couple of things going on here, and one is easily remedied
The very first step in troubleshooting a broken appliance happens long before the tech sets foot in the customer's home. In fact, it can happen even before the tech knows about the service call. We're talking about formulating a problem statement.
What I mean by a problem statement is very specific. A valid problem statement answers these two questions: "What is the appliance not doing that it should be doing?" and/or "What is the appliance doing that it shouldn't be doing?" It doesn't go b
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
What we call Parts-Changing Monkeys (PCMs) around here at Appliantology are techs who rely on pattern recognition, tech myths, and blind luck to make their repairs. Case in point with this example of a GE ZGU385 gas cooktop, where said PCM figured he would get lucky by replacing a couple of components that seemed related to the problem, apparently without any troubleshooting beforehand.
Spoiler: he didn't get lucky.
Real technicians don't rely on luck to get things fixed. We rely on kn
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
Happy Thanksgiving from all of us on Team Samurai!
I'm thankful for a year of Appliantology members keeping each other sharp and preventing us all from devolving into turkey techs. It's due to this fine community that we're not the ones in the oven.. this time.
Here's to another great year!
Gas burners are a whole little microcosm within appliances with some interesting technology that we don't see much elsewhere. In this webinar recording, we cover how to troubleshoot various cooktop ignition systems, covering topics such as:
DSI systems
Single-point ignition
Reignition systems
Continual sparking after a flame is established
Applying the Ten-Step Tango to real-world problems
...and more!
Click below to check out this webinar record
In this two-part Master Samurai Tech webinar series, we explore the nuances of sealed system diagnostics. Specifically, we're covering the nitty-gritty of applying our understanding of sealed system thermodynamics to real-world sealed system failures, such as refrigerant leaks, overcharges, and inefficient compressors.
Sealed System Diagnostics, Part 1
Sealed System Diagnostics, Part 2
Topics covered in the first part include:
Sealed system temperatures and pressure
Come on a journey with me as we explore just how tangled your circuit analyses can get when you're confronted with conflicting information in a tech sheet.
Here's the Samsung washer schematic we're working with:
Nothing crazy here -- this is pretty standard stuff to see on a Samsung schematic. But when it gets weird is when you try to trace out the power supplies of various loads and board on the schematic with the help of the pinouts elsewhere in the same tech sheet.
Here's
When it comes to troubleshooting BLDC motors and inverters, there's usually a standard strategy. You check the input to the inverter (a good 120 VAC power supply and a PWM signal from the main control) and you make sure the motor windings are in spec and all the same resistance. But what about measuring the output of the inverter?
This is certainly possible to do, and it can be a useful measurement, especially in hairier inverter troubleshooting scenarios. But before we get into that, let's
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
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