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Son of Samurai's Blog

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Entries in this blog


BLDC Motor Configurations, FG signals, and PWM signals

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

Bubble, Dew, and Glide in Refrigerants

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

Diodes in AC Circuits

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

Samurai's Picks: Quickly find the best tech info on Appliantology!

Appliantology is a big place, and there's valuable technical info constantly being posted in the forums and the blogs. But techs are busy folks, and we know that you don't always have the time to read through everything that's going on at the site. That's why I want to direct you to your new favorite page at Appliantology: Samurai's Picks. Accessible at any time from the main menu bar, Samurai's Picks is the go-to place where you can find content from the site that's hand-curated by u

Troubleshooting Thermistors, Identifying EEPs, and More...

When you want to measure the voltage across a component, where do you go to do that? Do you just resign yourself to disassembling the machine until you have access to that component? If you want to troubleshoot like a real tech, you use EEPs -- that's Electrically Equivalent Points. Identifying EEPs requires both being able to skillfully read a schematic and having a solid understanding of how electricity works. By doing this, you eliminate all unnecessary disassembly, increasing the profit

Is 120 VAC Really 120 Volts?

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

Know your Multimeter: a Short Breakdown of Every Meter Function

Let's take a look at a multimeter and talk about what each function does and what it's good for. This is specifically for a Fluke 116 multimeter, so if you have a different meter, you might see a slightly different array of functions. But this will be representative of a typical multimeter. LoZ: That stands for "low impedance". This is the loading function of your meter, meaning that it allows you to do voltage measurements that actually put a load on the circuit, allowing for a small

Educating Customers About Self Clean

Self-clean sounds like a great idea, right? Just push a button and watch your oven burn away all that caked-on grease and charred food.It certainly makes for a good selling point. But is this no-hassle cleaning feature really all it's cracked up to be? And what is the best way for the customer to use it (if at all)? First off: does it actually work? Can the oven clean itself just by getting really hot? Yes, definitely. Self-cleaning isn't just a gimmick, and when used properly, it does actu

How to Identify Unfamiliar Parts in Schematics

Take a look at the cooktop schematic below. I don't know about you, but "tranformator" isn't a familiar term to me. it certainly sounds like a transformer, but why would a transformer be necessary in a 240 VAC cooktop element circuit? The best thing to do here is to look up the part numbers for the "transformator" as well as other key components, such as those cooktop switches that the transformator is supplying power to. Then we can use a parts site to look at physical pictures

What You Need to Know to Repair Internet-Connected Appliances

Internet-connected appliances aren't a niche anymore. They're made by just about every brand out there, from Samsung to Whirlpool and beyond, so if you want to stay in the appliance repair game, you've got to know how they work. Lucky for you, this post is going to break down what you need to know to work on them. The key thing to keep in mind is this: internet-connected appliances are not that much more complicated than normal appliances. As long as you grasp a few fundamental concepts, th

Identifying Sensing Wires in Schematics

Have you ever noticed some connections on a schematic that just look plain unnecessary? Take a look at CN1 on this diagram. If you trace out those three wires, it may not be immediately obvious to you what the point of them is. Let's look at each connection individually, starting with pin 1. Well that looks pretty standard. It takes a direct path to neutral with no components in between. Nothing unusual about that -- the board needs its own neutral supply in order to run, a

Son of Samurai

Son of Samurai


Follow These Two Rules for Successful Part Replacement...

When it comes time to perform the repair and install a new part, the last thing you want is a surprise throwing a wrench in your plans. All the unexpected twists and turns should have already been dealt with during your troubleshooting. Ideally, performing the repair itself should just mean doing as little disassembly as possible, installing the new part, and collecting your repair fee. While there will always be unforeseen problems every now and then, there are a couple rules of thumb to a

Son of Samurai

Son of Samurai


PSC Motors and How to Properly Test a Capacitor

PSC (Permanent Split Capacitor) motors are nifty pieces of technology that you'll most often encounter in Whirlpool's VWM washers. They operate a bit differently from your typical split-phase motors. Rather than having a dedicated start winding and run winding, with each winding having different specifications, PSC motors have two windings that are physically identical. The only difference between them is in what direction the windings are wound. Another big difference between PSC motors an

Son of Samurai

Son of Samurai


What are TMR sensors and how are they different from Hall Effect sensors?

New technologies are never invented specifically for household appliances. We always get hand-me-downs. But just because a technology was used first in a different field doesn't mean that we're familiar with it already when it reaches appliances. TMR (tunnel magentoresistance) sensors are one such example. Coming to us from the world of computer electronics, they serve the same purpose as Hall Effect sensors but work completely differently. A TMR sensor consists of two ferromagnets sep

Son of Samurai

Son of Samurai


Spot the Error in this Schematic...

Here's a timing chart and a schematic. See if you can spot the problem... (HINT: it's in the motor circuit.) Did you see it? If you did, bravo! Your schematic-reading skills are pretty sharp. If not, don't worry -- I'll step you through it. Like I said, the error in the schematic is in the motor circuit -- specifically the start winding. Like any good tech, I'm going to do a load analysis on that winding to see what's up. Line and neutral both have to go through

How to Measure Voltage Drop Across Thermistors

All of us techs are carrying around multimeters these days, and that means we have several different voltage measurement settings available to us at any given time. Usually these are DC voltage, AC voltage, and LoZ (low input impedance). Each of these functions has a specific use, and part of taking a voltage measurement is picking the correct setting for the job. LoZ is by far the most common voltage function you should be using. In fact, there is almost never a time when you should do an

Son of Samurai

Son of Samurai


[Webinar Recording] How to Run an Appliance Repair Business During a Lockdown

With the ongoing COVID-19 crisis, things are changing quickly. No matter how long or short the actual pandemic lasts, everything won't just go back to how it used to be, and if we appliance repair techs want to stay in business, we will have to adapt. What exactly that adaptation looks like remains to be seen, but Team Samurai has been in the business long enough to have some solid ideas about it. Heavy sanitation precautions are something that is already happening and will continue to beco

Son of Samurai

Son of Samurai


Pop Quiz: What's Wrong with This Defrost Drain?

If you cracked open a freezer and saw the defrost drain looking like this, what would be your immediate reaction? Do you see what the problem is? Take a closer look... Have you figured it out? The deal with this defrost drain is... There is no problem. This is a clear, perfectly normal-looking defrost drain. You can see a little evidence of some water pooling and freezing, but the amount is well within acceptable limits. Based on a visual inspection, there is no issue

Son of Samurai

Son of Samurai


How to Correctly Measure Dryer Vent Airflow

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

How would you test these water valves?

How would you go about troubleshooting the valves? As always, we should start with a load analysis on your load (or in this case, loads) of interest. That means identifying how each valve gets line and neutral. (The wire marked with a blue N connects directly to neutral). You should immediately see that something is off. How do the IM and water valves get neutral? The answer is that someone over at Whirlpool made a whoopsie when drawing this schematic. There should be a line

Can a Range Run on a 9 Volt Battery?

Here's something you don't see every day: a gas range that is powered only by a 9 volt battery. Pretty nifty, huh? @Littletexan told us about his encounter with this one in this post from a couple weeks ago. Let's look at some of the unique aspects of this model. We'll start, as always, with the schematic: Well that's about as simple as it gets! All mechanical controls -- nothing too fancy going on here. One thing I will point out is that, while the schematic seems to show a

Watch Out for this LG Control Board Booby Trap

@LearningTech dropped a great tip in The Dojo a little while back: not all LG control boards can be updated after a universal compressor is installed. If you're planning on doing sealed system work on these machines, you're going to want to check the list below to see if your model's PCB can be updated. Otherwise, you might be in for a nasty surprise. LearningTech also provided a handy image showing where you can find a PCB's manufacturing date: Want to be in on cool tech t

Here's What Loading Down Looks Like and How to Troubleshoot It

Most of you have probably heard about loading down before -- when one failed DC component causes a ripple effect that keeps other DC components from functioning properly until the failed component is removed. But what does that actually look like in practice? And how do you go about troubleshooting it? To answer these questions, let's take a look at a straightforward, real-world example of loading down (taken straight from this topic at Appliantology). @marshall450 ran into what seemed

Son of Samurai

Son of Samurai


The Big Differences Between NTC and PTC Thermistors

In the appliance repair world, we deal with two different kinds of thermistors: NTC (Negative Temperature Coefficient) and PTC (Positive Temperature Coefficient). Don't know what those terms mean? Don't worry, I'll break it down for you. Despite both being thermistors, the only real similarity between NTCs and PTCs is that the resistance of both changes in response to temperature. Beyond that, they work quite differently and serve very different functions. Here's what a typical NTC the

Son of Samurai

Son of Samurai


The Vital First Step to Troubleshooting Any Refrigerator

No matter what refrigerator problem you're called out for, no matter if it's for a warm freezer or a noisy fan or a leaking dispenser, there's one simple step that should you should always do before anything else -- before you or the customer even opens the doors of the machine: Measure the compartment temperatures. Simple, right? So why am I writing a blog post about it? Well, a lot of techs don't see why this is a step that you must always take when troubleshooting a refrigerator. Do

Son of Samurai

Son of Samurai

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