It seems like large-screen cheap meters are really catching on. [TheHWcave] does a very detailed review of a KAIWEETS KM601, which is exactly the same as a few dozen other Chinese brands you can get from the usual sources. You can see the review in the video below.
If we learned nothing else from this video, we did learn that you can identify unmarked fuses with a scale. The fuses inside were not marked, so he wanted to know if they appeared to be the right values. We would have been tempted to just blow them under controlled conditions, but we get he didn’t want to destroy the stock fuses until after testing.
There was a time when calculators became so powerful it was hard to tell them from little computers. The same thing seems to be happening now with multimeters. They now often have large screens and basic oscilloscope functionality. The specs keep getting better. While early cheap scopemeters were often relatively low frequency, many are now claiming bandwidths that would have cost quite a bit a few decades ago. A case in point is the Mustool MDS8207 which [IMSAI Guy] reviews and does a teardown of in the videos you can see below. It claims a 40 MHz bandwidth with 200 megasamples per second on a single channel.
The only downside in the claimed specifications is that the sensitivity isn’t great given that the lowest setting is 500 mV per division. Then again for a meter that runs under $100, any scope function would seem to be a bonus. The meter does all the other things you expect a meter to do these days, such as reading voltage, frequency, capacitors, temperature, etc. The response time of the meter is relatively slow, but you can get used to that.
Hackers are often of the sentimental type, falling in love with the look and feel of quality old hardware. Of course, sometimes that older hardware needs a little TLC to keep it running in the modern world. [Lex] had a beautiful vintage multimeter that sadly had a broken screen, and set about a nifty repair to restore it to working condition.
It’s a handsome thing.
The HSN Avometer DA116 is a handsome thing, controlled with two dials and featuring a clean two-tone aesthetic. Even the font on the PCB’s silkscreen is gloriously pretty (can anyone ID that?). However, the original LCD was non-functional. A direct replacement part was sadly unavailable. Instead, to rectify this, [Lex] first hunted down another segmented LCD screen that had the same segment layout.
However, the new screen had a completely different pinout to the original part. Thus, after taking some notes and figuring out what all the pins did, [Lex] whipped up an adapter board to carry the new screen. With some protoboard, some pin headers, and a bunch of point-to-point wiring, the new screen worked just fine, and [Lex] had a functioning vintage meter once again!
Here’s an interesting and detailed teardown and repair of a Keithley 2001 7.5 Digit multimeter that is positively dripping with detail. It’s also not every day that we get to see someone using x-ray imaging to evaluate the extent of PCB damage caused by failed electrolytic capacitors.
Dark area is evidence of damage in the multi-layer PCB.
Sadly, this particular model is especially subject to that exact vintage electronics issue: electrolytic capacitor failure and leakage. These failures can lead to destroyed traces, and this particular unit had a number of them (in addition to a few destroyed diodes, just for good measure.) That’s where the x-ray machine comes in handy, because some of the damage is hidden inside the multi-layer PCBs.
[Shahriar], perhaps best known as [The Signal Path], narrates the entire process of fixing up the high-quality benchtop multimeter in a video, embedded below (or you can skip directly to the x-ray machine being broken out.) [Shahriar] was able to repair the device, thanks in part to it being in relatively good shape, and having the right tools available. Older electronics are not always so cooperative; the older a device is, the more likely one is to run into physical and logical standards that no longer exist.
We’ve noticed lately that some cheap meters have gone to having big colorful screens. The screens aren’t dot matrix, but still have lots of graphics that could be useful or could be distracting eye candy, depending. The really cheap ones seem more like a gimmick, but [OM0ET] took a look at one that looked like a fair midrange instrument with some useful display features, the GVDA GD128.
A lot of the display shows the current function of the meter. No need for an expensive multiposition switch or rows of interlocking pushbuttons. Many of these new meters also have non-contact voltage sensors, which is handy. Otherwise, it looks like a pretty conventional cheap meter. Continue reading “Multimeters Go Big Screen”→
A few years ago [Mechatrommer] got one of the low-cost Aneng Q1 multimeters and has converted it into a bench top meter. He first tried and failed to do an LCD modification and set it aside. It remained in a storage box until he needed another meter to repair his rubidium frequency standard. Finding that off-the-shelf bench multimeters were literally off-the-shelf — they were too deep for his bench — he decided to take matters into his own hands.
He dug out the dismantled an Aneng Q1 and undertook a more drastic modification than before, slicing the multimeter into three pieces and mounting each piece in a new enclosure. The power-draining back-lit display of the Q1, problematic in a battery-powered handheld meter, isn’t an issue in a bench top design. [Mechatrommer] replaced the battery pack with a mains powered supply. Next he reconnected all the signals which had been interrupted by the bandsaw, and now the meter lives again.
The resulting meter is pleasing enough (ignore the sideways input jacks) and looks like a typical piece of home-brew test gear. The enclosure has a lot of empty space, which he uses to stow test leads and sandwiches (we saw a similar storage compartment in [Dave Jones]’s recent teardown of a portable Fluke 37 multimeter). Kudos to [Mechatrommer] for coming up with this unusual conversion project.
I’m moving, and in the process of packing all of my belongings into storage boxes to disappear into a darkened room for the next year. Perhaps I could become one of those digital nomads I hear so much about and post my Hackaday stories from a sun-kissed beach while goldfish shoals nibble at my toes. But here in a slightly damp British autumn, box after box of a lifetime’s immersion in tech needs sorting and directing. Why on earth did I hang on to three Philips N1500 VCR system video cassette recorders from the early 1970s! (Don’t worry, those have found a good home.)
Say Hello To An Old Friend Of Mine
Instantly recognisable, the AVO 8
As I was packing up my bench, I happened upon a multimeter. I have quite a few multimeters and this isn’t the first time I’ve written about these indispensable instruments, but this one’s a little special.
It’s a treasure from my youth, that most venerable of British test equipment: the AVO 8. This was the ubiquitous multimeter to be found in all manner of electrical and electronic workshops across most of the 20th century, and remains to this day one of the highest quality examples of its type.
It’s a relatively huge Bakelite box about 190mm x 170mm x 100mm in size, and it is instantly recognisable by its dual rotary selector switches and the window for viewing the needle, which forms a characteristic circular arc kidney shape.
The earliest ancestors of my meter appeared in the 1920s, and the first model 8 in the early 1950s. Mine is a Mk III that a penciled date on the inside of its meter movement tells me was made in November 1965 and which I bought reconditioned from Stewart of Reading in about 1991, but manufacture continued until the last Mk VIII rolled off the production line in 2008. It’s to my shame that my AVO is a bit dusty and that maybe I haven’t used it much of late, but as I picked it up all the memories of using it to fix dead TV sets and set up optimistic experiments in radio came flooding back. If there’s one instrument that connects me to the youthful would-be electronic engineer that I once was, then here it is. Continue reading “Ode To An AVO 8 Multimeter”→
