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Tech Circuit Donors

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Alphabetical Links to all Tech Circuit™ Blogs and Articles

About the Tech Circuit™ The Tech Circuit’s mission is to continuously improve and maintain the Field Technician’s electrical diagnostics aptitude. The need to provide electrical and electronic related diagnostic solutions in the field has become increasingly unavoidable. Developing an innate understanding of how electricity works greatly empowers you when encountering such scenarios. Below is a […]

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Appliance Technician Cheat Sheets – Full List

Appliance and HVAC Technician Electrical References Below are links to all Appliance Technician Quick-References to date. Feel free to bookmark/share this page or the individual pages below. These are updated as often as needed: 120v Point-to-Point Troubleshooting Cheat Sheet – CLICK HERE 120V Point-to-Point Voltage Pen Diagnostics Cheat Sheet – CLICK HERE 240v Point-to-Point Troubleshooting […]

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Donate to the Tech Circuit

The Tech Circuit’s mission is to better educate Appliance and HVAC Technicians in the area of electrical and electronics diagnostics and repair. There is clearly an need for this better education – and the effort is endless. Although I thoroughly enjoy this mission, it does take time to maintain TechCircuit.org and the Tech Circuit Youtube […]

Voltage Pen Magic – How to Make the Best of your NCV Tester

Introduction This blog will introduce the many ways that an NCV voltage pen can be used to diagnose electrical circuits. In fact, you might be surprised as to how versatile and useful the voltage pen can actually be. I’ll show you how this simple device can be used to detect Ghost Voltages, detect Compromised Voltage […]

What is a Voltage Divider?

What do floating neutrals, gas dryer valve circuits, Whirlpool electric dryer cool-down circuits, loose terminal block connections, shorted elements, and failing relay contacts all have in common? As the title of this articles suggests – the ever-present voltage divider. They’re everywhere and reside in multiples in every appliance you encounter. They’re not only present in […]

Appliance Repair Electrical Theory Learning Quiz

Introduction This quiz is designed to help Appliance technicians learn, test their knowledge, or just provide a review of their existing knowledge of electrical theory as it applies to appliance repair. Each question will have an associated answer – helping solidify your knowledge of electricity. So let’s test your knowledge. How Many Questions can you […]

Finding an Open or Loose Neutral with a Voltage Pen

The title says it all. A voltage pen can be much handier than some Technicians realize. Yes, they can be easily used to locate an open or loose (compromised) neutral in in a voltage source. THIS BLOG IS INTENDED FOR APPLIANCE TECHNICIANS ONLY. ALWAYS USE APPROPRIATE SAFETY PRECAUTIONS WHEN WORKING WITH ELECTRICITY. About Neutral Neutral, […]

How does an SMPS Power Supply Work?

In this article, we’ll go into detail, how an SMPS or Switched Mode Power Supply works on a control board. We’ll talk about how the input filter works, initial rectification or conversion of AC into DC voltage, the switching circuit, high frequency transformer and galvanic isolation, feedback control circuit, and output rectification and filter. We’ll […]

Testing Diodes with a Multimeter

Introduction In this blog, we will describe what diodes are, how they function, and how to test them. We will identify two of the most common types of diodes encountered by Technicians, and describe how to test them in circuit and out of circuit. Additionally, we will discuss the most common ways that diodes fail […]

Four ways Ohms can Lie

What does it mean when we say “Ohms can Lie”? It’s more of a colloquial expression suggesting that relying on static resistance may not give you enough information about how some components behave when energized. For example, when you measure the resistance of a component, and its “opposition to current flow” varies when subjected to […]

ESR Lookup Table Cheat Sheet

This page serves as a quick reference for Field Technicians when measuring electrolytic capacitor Equivalent Series Resistance (ESR) when using the Atlas ESR 70 meter. For electrolytic capacitors there are typical ESR values associated with particular capacitances. When measuring ESR in the field, this helpful reference table will facilitate easy lookup so that you can […]

How does a Control Board Work?

Important Note Never attempt to repair circuit boards in appliances or HVAC systems unless you are directly supervised by a licensed professional engineer and doing so under approved ISO and UL processes. Anatomy of a Control Board In this article, I’ll do a detailed walkthrough of a common refrigerator control board – the WR55x10942, go […]