Imagine this. A young person comes to you wanting to get started in the electronic hobby. They ask what five things should they buy to get started. Make your list. We’ll wait. We bet we can guess at least two of your items: a multimeter, and a soldering iron. [LearnElectroncsRepair] recently showed us a review of the Zotek Zoyi ZT-N2 which is a soldering iron and a multimeter in one unit. You can watch the video review below.
Honestly, when we heard about this, we didn’t think much of the combination. It doesn’t seem like having your probe get red hot is a feature. However, the probe tip replaces the soldering iron tip, so you are either soldering or measuring, but not both at the same time.
In a world of digital monotony, the Avo DA14 digital multimeter, with its vintage nixie tube charm, is a refreshing gem. Recently refurbished by [Thomas Scherrer], this multimeter video review is a blend of nostalgia and tech savvy. The DA14 not only has style, but substance — delivering resistance, current, and voltage measurements that make you wonder why more multimeters didn’t stick with this stylish glow.
As [Thomas] starts by powering up the DA14, we were instantly captivated as the Nixie tubes illuminate in their retro orange. With each twist of the dial, he demonstrates just how intuitive the multimeter is to operate, walking us viewers through each function while giving some extra love to its calibration process—a neat front-panel potentiometer that requires just a touch of finesse to get perfect readings.
But, as with all good tinkering tales, things go downhill when issues with analog inputs and the display pop up. A teardown reveals a beautifully complex inner assembly of transformers, rectifiers, and circuit boards, giving the DA14 its impressive yet fragile structure. When the critical defective display chip is found, hopes for a full repair dim. His story ends without a revival, but if you want to see a similar attempt that did get resurrected – albeit without those nixie digits – take a look at this LCD transplant we covered previously.
Frustrated by his Aldi multimeter’s backlight turning off after just 15 seconds, [Steg Steg] took matters into his own hands. His solution? He added a manual toggle switch to control the backlight, allowing it to stay on as long as needed. He began by disassembling the multimeter—removing the outer bumper and a few screws—to access the backlight, labeled “BL.” He identified the voltage regulator outputting 2.8 V, desoldered the red wire, and extended it to install the switch.
On his first try, he successfully drilled a spot for the SPST switch. To fit the switch into the multimeter’s rubber bumper, he used a circular punch, although his second hole wasn’t as clean as the first. Despite this minor setback, the modification worked perfectly, giving him complete control over his multimeter’s backlight without the original 15-second timeout.
Multimeters are a bit like potato chips: you can’t have just one. But they’re a lot more expensive than potato chips, especially the good ones, and while it’s tempting to just go get another one when you need to make multiple measurements, sometimes it’s not practical. That’s why something like this 2×4 relay-based multiplexer might be a handy addition to your bench
In this age of electronics plenty, you’d think that a simple USB relay board would be easy enough to lay hands on. But [Petteri Aimonen] had enough trouble finding a decent one that it became easier to just roll one up from scratch. His goal was to switch both the positive and negative test leads from up to four instruments to a common set of outputs, and to have two independent switching banks, for those times when four-lead measurements are needed. The choice of relay was important; [Petteri] settled on a Panasonic DPDT signal relay with low wetting current contacts and a low-current coil. The coils are driven by a TBD62783A 8-channel driver chip, while an STM32 takes care of USB duties.
The mechanical design of this multiplexer is just as slick as the electrical. [Petteri] designed the PCB to act as the cover for a standard Hammond project box, so all the traces and SMD components are mounted on the back. That just leaves the forest of banana-plug binding posts on the front, along with a couple of pushbuttons for manual input switching and nicely silkscreened labels. The multiplexer is controlled over USB using the SCPI protocol, which happily includes an instrument class for signal switchers.
Inspired by electronics repair videos on YouTube, [Steven Leibson] recently found himself hunting down something to fix on eBay. This ‘something’ ended up being a certified classic: a Keithley Model 179 digital multimeter from 1978. Listed as non-functional, the unit arrived at his door for less than $50. There weren’t any exciting pops or smoke when he powered it on, but the display seemed to be showing nothing but random nonsense.
The meter has a convenient calibration sequence printed on its electrostatic shield cover and a deadly exposed AC line fuse in the upper left part of the photo.
Ultimately reviving this little piece of history was quite simple, with the main issue turning out to be a dodgy inter-board connector between the main and display boards. After admiring an old repair attempt made on the component, he removed both the male and female connectors, replacing them with new ones.
This uncovered issues with the PCB, as the FR4 material and the traces on it had begun to delaminate, probably due to the old adhesive giving up due to age. With pretty low trace density this wasn’t anything that a bit of care couldn’t work around, fortunately.
Before finding this dodgy connector, [Steven] first tried to clean the front mechanical connectors, which took multiple sessions. This was followed up by oiling the mechanism. With the connector fixed and some cleaning, the meter’s display now read correctly. It still has some issues with starting up though, which [Steven] reckons are due to the old capacitors in the device.
Presumably some recapping will round off this fun device revival experience, but for the time being a Keithley Model 179 has been saved from e-waste, to inspire generations to come.
Some things go together, like chocolate and peanut butter. Others are more odd pairings, like bananas and bacon. We aren’t sure which category to put [IMSAI Guy]’s latest find in. He has a microscope with a built-in digital multimeter. You can see the video of the device in operation below.
The microscope itself is one of those unremarkable ten-inch LCD screens with some lights and a USB camera. But it also has jacks for test probes, and the display shows up in the corner of the screen. It is a normal enough digital meter except for the fact that its display is on the screen.
If you had to document test results, this might be just the ticket. If you are probing tiny little SMD parts under the scope, you may find it useful, too, so you don’t have to look away from what you are working on when you want to take a measurement. Although for that, you could probably just have a normal display in the bezel, and it would be just as useful.
At about $180 USD, it’s not exactly an impulse buy. We wonder if we’ll someday see an oscilloscope microscope. That might be something. These cheap microscopes are often just webcams with additional optics. You can do the same thing with your phone. If you don’t need the microscope, but you like the idea, can we interest you in a heads-up meter?
Multimeters are indispensable tools when working on electronics. It’s almost impossible to build any but the most basic of circuits without one to test and troubleshoot potential issues, and they make possible a large array of measurement capabilities that are not easily performed otherwise. But when things start getting a little more complex it’s important to know their limitations, specifically around what they will tell you about circuits designed for high frequency. [watersstanton] explains in this video while troubleshooting an antenna circuit for ham radio.
The issue that often confuses people new to radio or other high-frequency projects revolves around the continuity testing function found on most multimeters. While useful for testing wiring and making sure connections are solid, they typically only test using DC. When applying AC to the same circuits, inductors start to offer higher impedance and capacitors lower impedance, up to the point that they become open and short circuits respectively. The same happens to transformers, but can also most antennas which often look like short circuits to ground at DC but can offer just enough impedance at their designed frequency to efficiently resonate and send out radio waves.
This can give some confusing readings, such as when testing to make sure that a RF connector isn’t shorted out after soldering it to a coaxial cable for example. If an antenna is connected to the other side, it’s possible a meter will show a short at DC which might indicate a flaw in the soldering of the connector if the user isn’t mindful of this high-frequency impedance. We actually featured a unique antenna design recently that’s built entirely on a PCB that would show this DC short but behaves surprisingly well when sending out WiFi signals.
