Monday, December 6, 2021

The Realist: Tools for Diagnosing and Repairing Electrical and Electronic Problems

This is the second in a series by the Realist on tools for the prepper. You can find Part 1, about common hand tools for home repair, here. The Realist writes:

 From left to right, wall outlet circuit tester (above), USB multimeter (bottom), non-contact voltage tester, Fluke 87 III multimeter (my primary multimeter) with test leads, and Fieldpiece SC53 HVAC multimeter with test leads.

    Disclaimer: All products mentioned in this article were purchased by myself. I did not receive samples, evaluation models, or other compensation from any manufacturer or retailer. I have no formal relationship with any manufacturer or retailer mentioned in this article - I have only been an arms-length customer.

    All brand names and product names used in this review are the trade names,service marks, trademarks, or registered trademarks of their respective owners.

    I am not a licensed or certified tradesman. Further, this article reflects my unique circumstances and subjective opinions with regard to performance and other characteristics of the products being discussed. Your mileage may vary.

    Growing up, my father taught me how to fix many things. Since then, my repair skills have continued to improve. Besides having the knowledge of how to fix things, having the appropriate tools is necessary to fix many things.

    As the economy worsens, the need to diagnose and repair things yourself, rather than paying others to make repairs or discarding a failed item, will become increasingly necessary. Being able fix things myself has saved me a bundle of money.

    You learn how to repair things by doing repairs. Now, there are many excellent YouTube videos that explain how to perform various repairs, and you can dramatically shorten the learning curve by watching a few videos on a specific repair topic.

    Diagnosing electrical problems can benefit from the use of specialized tools, but don't forget to engage your brain, too.

Your Brain - Careful Observation

    Many electrical problems can be solved by nothing more than careful observation.

    A few years ago, my modern LCD television started having the sound cut out in one or both speakers - very annoying - and it got progressively worse. So, I decided to open it up to figure out what was going on. Given how the problem had progressed I expected to find cracked solder joints. (Thermal cycling from turning on and turning off many devices can introduce stresses that can eventually crack solder joints, and reflowing the cracked solder joints will fix the problem.) I carefully examined the solder joints in the audio portions of the circuitry, but saw nothing that looked amiss. Then I noticed that the spade connectors on the end of the wires connected to the speakers seemed loose, really loose. I unplugged them, squeezed them slightly with pliers so they would connect firmly, and reattached the wires to the speakers. I have not had any audio problems with that TV since then.

    In my experience, many electrical and electronic problems are really mechanical problems such as loose connections or broken wires.


    Frequently, I have to diagnose apparent electrical problems. To do this, I usually use a multimeter. A multimeter has the ability to measure voltage, resistance, and current. Many multimeters have the ability to perform additional tests.

    My first multimeter was an inexpensive analog model I purchased as a kit from Radio Shack. I used it for many years before advancing to a digital multimeter.

    For some tasks, an analog meter is actually superior to a digital multimeter. If you are wanting to observe a fluctuating electrical occurrence, such as varying voltage from a flakey alternator, being able to watch a needle move is more informative than watching numbers change on a digital display. Some digital multimeters incorporate a bargraph along the bottom of the display to simulate the movement of the needle in an analog multimeter.

    Today, most multimeters are digital, with analog multimeters being less common. 

    Digital multimeters range in price from almost free (remember the free-with-purchase Harbor Freight digital multimeters?) to models costing thousands of dollars. (Those free (regularly priced $5-6) Harbor Freight multimeters were terrible quality and unsafe to use for anything beyond automotive voltages (12 VDC).)

    As a practical matter, even the most basic multimeter can perform a variety of home and automotive diagnostic tasks. The most common tasks I perform with a multimeter include verifying voltage in a circuit, measuring the voltage output from a battery (is it dead or not), checking for broken wires ("continuity check" using the resistance setting), and checking to see if a filament light bulb is burned out or not - yes, sometimes it is not obvious that the bulb has burned out.

    As mentioned above, multimeters range in price from practically free to thousands of dollars. In general, I would avoid any multimeter costing less than fifteen or twenty dollars. For fifteen to twenty dollars, you can buy a basic digital multimeter that has most of the same functions as the Harbor Freight free multimeter, but is better made and incorporates some added safety features.

    My primary multimeter is the Fluke 87 III, which is overkill for most home and automotive repair activities. Pictured, I also show an older Fieldpiece SC53 multimeter, the style of multimeter typically used by HVAC technicians, which includes a clamp-on current meter used for measuring the current draw of motors in HVAC systems.

    (Fun fact: Many of the low-cost digital multimeters, such as the "free" Harbor Freight multimeter, are based on clones of the 1970s Intersil ICL7106 chip.)

USB Multimeter

    Another very useful electrical tool I use regularly is a USB Multimeter - sometimes called a "Charge Doctor." This is a specialized device you plug into a USB power source, then plug your USB powered device or its charging cable into the USB Multimeter. These devices display voltage and current. (My favorite model is here, but I also use this model)

    USB multimeters do two things. They tell you if your USB power source is actually operational, and they tell you if your USB powered device is actually drawing current (e.g. charging).

    I use a USB Multimeter to check cell phone charging cables (the device plugged into the cable is drawing current), to verify that a device is charging, and to determine when a device is fully charged (as opposed to relying on an indicator light on the device to indicate it is fully charged).

    Once you start using a USB multimeter, you will wonder how you ever got along without one.

Non-Contact Voltage Tester

    Another useful device to have around the house when diagnosing electrical problems, or determining whether or not a circuit is live, is a non-contact voltage tester. The main value of this tool is safety - verifying a circuit is dead before starting to work on it. "Non contact", means you hold the tip of the tool near a wire or wall outlet, and it will beep and flash an LED if an alternating current (AC) voltage is present.

    Yes, you could use a multimeter to verify a circuit is dead, but a non-contact voltage tester is quicker and doesn't require direct access to the wires or terminals.

    Harbor Freight makes a five dollar non-contact voltage tester. I had the previous model, but found it to be a bit flakey. I now have the Sperry Instruments VD6505 in my tool kit.

    There are also multimeters that incorporate a non-contact voltage tester into the body of the multimeter, such as the pictured Fieldpiece SC53, so you can have less tools to juggle when diagnosing an electrical problem.

Wall Outlet Circuit Tester

    I don't use a wall outlet circuit tester very often, but it is a handy gadget to have on hand. You simply plug it into a three-prong wall outlet and it will indicate whether or not the outlet is wired properly. It has three neon bulbs that indicate the state of the outlet. I have primarily used it to test the outlets when I move into a new home. It is also useful to verify that you properly wired everything after replacing a wall outlet.

    Wall outlet circuit testers are fairly inexpensive. I found one on Amazon for less than seven dollars, and Harbor Freight and Walmart have them for less than five dollars. Since I last looked at these testers, many now have a GFCI (ground fault circuit interrupter) test button to test the GFCI outlets that are now common in kitchens and bathrooms.


    I regularly use a multimeter to solve a variety of electrical problems. A multimeter is really a necessity if you do anything with electricity. Similarly, I use a USB multimeter when dealing with USB powered/charged devices. The other tools mentioned in this article are nice-to-haves that make working with electricity safer and easier.

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