Should You Be Able To Repair It? We Think So.

August 11, 2021 by Jenny List 179 Comments

You own it, you should be able to fix it. So much equipment on sale today has either been designed to be impossible to maintain, unnecessarily too complex to maintain, maintainable only with specialist tooling only available to authorised service agents, or with no repair parts availability. It’s a hot-button issue in an age when sustainability is a global concern, so legislators and regulators worldwide now finally have it in their sights after years of inaction and it’s become a buzzword. But what exactly is the right to repair, and what do we want it to be?

Is It Designed For Repair?

A Nestle Dolce Gusto machine — For some reason, pod coffee makers are especially resistant to repair. Andy1982, CC BY 3.0

The first question to consider is this: does it matter whether or not you have the right to repair something, if it’s designed specifically with lack of repairability in mind? Consider a typical domestic pod coffeemaker such as a Tassimo or similar: despite being physically quite a simple device, it is designed to be especially complex to dismantle and reassemble. You just can’t get into it when something goes wrong.

Should it be the preserve of regulators to require design for easy repair? We think so. There are other forces working on the designers of home appliances; design-for-manufacture considerations and exterior appearance concerns directly affect the firm’s bottom line, while the end users’ repair experience is often at the bottom of the list, even though the benefit at a national level is obvious. That’s what laws are for.
Continue reading “Should You Be Able To Repair It? We Think So.” →

The O’Scope Restoration

August 1, 2021 by Al Williams 8 Comments

These days, a pretty nice oscilloscope can fit in your toolbox and even a “big” instrument is probably something you can tuck under your arm. But that hasn’t always been the case. Consider this old HP 150A, restored by [USagi Electric]. (Video, embedded below.)

The 10 MHz dual channel scope might not seem very high-tech today, but when HP rolled it out in the 1950s to challenge Tektronix, it was quite respectable. The $1,000 price tag just for the mainframe was pretty respectable, too. Unfortunately, the scope wasn’t very reliable with more than 50 tubes in it, and HP quickly had to develop new entries in the scope market.

Continue reading “The O’Scope Restoration” →

Rare Radio Receiver Teardown

July 30, 2021 by Al Williams 14 Comments

We’ll admit we haven’t heard of the AGS-38, it reminds us of the shortwave receivers of our youth, and it looks like many that were made “white label” by more established (and often Japanese) companies. [Jeff] found a nice example of this Canadian radio and takes it apart for our viewing pleasure. He also found it was very similar to a Layfayette receiver, also made in Japan, confirming our suspicions.

The radio looks very similar to an Eico of the same era — around the 1960s. With seven tubes, radios like this would soon be replaced by transistorized versions.

Continue reading “Rare Radio Receiver Teardown” →

Faulty Electrolytic Caps Don’t Always Look Bad

July 18, 2021 by Donald Papp 49 Comments

Old electrolytic capacitors are notorious for not working like they used to, but what exactly does a bad capacitor look like, and what kinds of problems can it cause? Usually bad caps leak or bulge, but not always. In [Zak Kemble]’s case, a bad cap caused his Samsung HT-C460 Home Cinema System to simply display “PROT” then turn itself off. Luckily, replacing the troublesome cap fixed everything, but finding the problem in the first place wasn’t quite so straightforward. A visual inspection of the device, shown open in the photo above, didn’t reveal any obvious problems. None of the capacitors looked anything out of the ordinary, but one of them turned out to be the problem anyway.

The output cap had developed an internal short, but visually looked fine.

The first identifiable issue was discovering that the -5 V supply was only outputting about -0.5 V, and there was a 6 V drop across two small 0805-sized resistors, evidence that something was sinking far more current than it should.

Testing revealed that the -5 V regulator wasn’t malfunctioning, and by process of elimination [Zak] finally removed the 470 uF output capacitor on the -5 V output, and the problem disappeared! Inspecting the capacitor revealed no outward sign of malfunction, but it had developed an internal short. [Zak] replaced the faulty cap (and replaced the others just to be safe) and is now looking forward to getting years more of use out of his home cinema system.

When a PSU gives up the ghost, bad capacitors are almost always to blame, but we’ve seen before that it’s not always easy to figure out which ones are bad. One thing that helped [Zak] plenty in his troubleshooting is finding a full schematic of the power supply, just by doing a search for the part number he found on it. A good reminder that it’s always worth throwing a part number into a search engine; you might get lucky!

Fixing Noisy Measurements On An Owon XDM2041 Bench Multimeter

July 14, 2021 by Maya Posch 21 Comments

After purchasing an Owon XDM2041 bench multimeter for an automated test setup, [Petteri Aimonen] was disappointed to find that at especially the higher mega Ohm ranges, the measured values were jumping around a lot and generally very inaccurate. Since this is an approximately $170 bench multimeter and Owon support wasn’t cooperating, [Petteri] set out to fix the issue, starting with a solid teardown.

As noted by [Petteri], there’s not a whole lot inside one of these multimeters. The main board with the guts of the whole system contains a GigaDevices GD32F103CBT6 MCU coupled with the star of the show: the HYCON Technology Corporation’s HY3131 multimeter chip. After a peek at the HY3131 datasheet, the culprit was quite apparent: while sampling the presence of mains voltage noise is usually suppressed through the selection of an appropriate crystal.

Unfortunately, instead of the recommended 4.9152 MHz crystal per the reference schematic for the HY3131, Owon’s engineers had apparently opted for a 4 MHz crystal instead, and so it’s essentially aliasing the line noise.

[Petteri] figured that the resulting sampling timing might work well enough with 60 Hz line frequency, but clearly with 50 Hz there was a lot of noise sneaking into the measurements. After swapping the crystal with a 3.072 MHz one, there was a marked improvement, as the plot shows.

Chip Transplant Brings Timex 2048 Back From Grave

July 12, 2021 by Tom Nardi 16 Comments

The 1984 Timex Computer 2048 that [Drygol] recently got his hands on was in pretty poor shape. Not only did it have the mangled exterior that comes from several decades of hard use and furious typing, but the internals appeared to be shot as well, with the machine showing nothing but vertical lines when powered up. Thankfully, this retro computer virtuoso was more than up to the challenge of bringing it back from the brink.

After a good cleaning and the installation of a reproduction front panel, the Timex was already looking much better. Unfortunately [Drygol] says he doesn’t currently have the equipment necessary to touch up the graphics and lettering on the key caps, but the fact that he had to qualify that statement with “currently” has us all sorts of excited to see what he’s planning down the line.

Of course beauty is only skin deep, and this particular TC-2048 was still bad to the bone. [Drygol] had a hunch its Z80 processor was dead, but after swapping it and its socket out, the machine still wouldn’t start. Though he did note that the garbled graphics shown on the screen had changed, which made him think he was on the right track. He then replaced all the RAM on the board, but that didn’t seem to change anything.

There isn’t a whole lot else to go wrong on these old machines, so the final step was to try and replace the ROM. Sure enough, after installing a new Winbond W27C512 chip with the appropriate software burned onto it, the nearly 40 year old computer sprang back to life.

Another classic computer saved from the trash heap, but it’s all in a day’s work for [Drygol]. Over the years we’ve seen him perform meticulous repairs on computer hardware that any reasonable person would have given up on. Even if you’re not into retro hardware, his restorations are always full of fascinating tips and tricks that can be applied when repairing gadgetry from whatever era happens to tickle your fancy.

Lightwave Multimeter Teardown

July 6, 2021 by Al Williams 2 Comments

You tend to think of test equipment in fairly basic terms: a multimeter, a power supply, a signal generator, and an oscilloscope. However, there are tons of highly-specialized test equipment for very specific purposes. One of these is the 8163A “lightwave multimeter” and [Signal Path] tears one part for repair in a recent video that you can see below.

If you’ve never heard of a lightwave multimeter, don’t feel bad. The instrument is a measuring system for fiber optics and, depending on the plugins installed, can manage a few tests that you’d usually use an optical power meter, a laser or light source, and some dedicated test jigs to perform. Continue reading “Lightwave Multimeter Teardown” →