Teardown

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Pre-exploded PSU close-up: shown is inductor with the heatsink it shorted against.

The Little Replacement PSU That Could: Kill A Microsoft Surface And Monitor

February 21, 2022 by 55 Comments

Recently [Big Clive], everyone’s favorite purveyor of anything electronic that’s dodgy, cheap, cheerful, decidedly crispy or any combination thereof, got sent a very dead external power supply unit. Being clearly a third-party PSU with poorly written and many (likely not truthful) safety approval markings on its label, this PSU had the dubious honor of having destroyed a Microsoft Surface computer as well as the monitor that was connected at the time.

In [Clive]’s video (also embedded after the break) the black and very crispy board is examined, showing a wealth of vaporized traces and plenty of soot. What’s however most fascinating is the failure mode: instead of something obvious like e.g. the main transformer between the primary and secondary side failing, here it would seem that an inductor (see heading image) on the secondary side had its insulation rubbed off and shorted on a nearby heatsink. A heatsink that just happened to be also electrically connected on the primary (mains-level) side.

Judging by the former owner’s report and aftermath, this led to a very sudden and violent demise of the PSU, with mains power very likely making its way into the unsuspecting Surface system and connected monitor. The number of ‘very nope’ design decisions made in this PSU are astounding, and a lesson for both aspiring EEs and anyone considering getting a ‘cheap’ third-party replacement PSU.

(Thanks to [Helge] for the tip)

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Soviet-Era Auto Dialler Uses Magnetic Rope Core Memory

January 13, 2022 by 12 Comments

We’ve seen a few interesting magnetic core memories on these fine pages over the years, but we don’t recall seeing too many user programmable magnetic core memory devices. This interesting Russian telephone auto dialer in its day would have been a very useful device, capable of storing and dialing forty user programmable 7-digit numbers. [mikeselectricstuff] tore into one (video, embedded below), and found some very interesting tech. For its era, this is high technology stuff. Older Russian tech has a reputation for incredibly ingenious use of older parts, that can’t be denied. After all, if it works, then there’s no need to change it. But anyway, what’s interesting here is how the designers decided to solve the problem of programming and recalling of numbers, without using a microprocessor, by using discrete logic and core rope memory.

This is the same technology used by the Apollo Guidance Computer, but in a user configurable form, and obviously much smaller storage capacity. The core array consists of seven, four-bit words, one word per telephone digit, which will be read out sequentially bottom to top. The way you program your number is to take your programming wire, insert it into the appropriate hole (one row related to numbers 1-20, the other row is shifted 1-20 for the second bank) and thread it along the cores in a weave type pattern. Along the way, the wire is passed through or bypasses a particular core, depending upon the digit you are coding for. They key for this encoding is written on the device’s lid. At the end, you then need to terminate the wire in the matching top connector, to allow the circuit to be completed.

As far as we can tell, the encoding is a binary sequence, with a special ‘stop’ code to indicate telephone numbers with less than seven digits. We shall leave further analysis to interested parties, and just point you at the Original manufacturer schematics. Enjoy!

Of course we’re not just going to mention rope core memory and the AGC without linking to a fantastic article about the very same, and if that’s wetting your appetite for making a rope core memory, here’s a little thing about that too!

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Old-school frequency counter

Edge-Mounted Meters Give This Retro Frequency Counter Six Decades Of Display

January 3, 2022 by 7 Comments

With regard to retro test gear, one’s thoughts tend to those Nixie-adorned instruments of yore, or the boat-anchor oscilloscopes that came with their own carts simply because there was no other way to move the things. But there were other looks for test gear back in the day, as this frequency counter with a readout using moving-coil meters shows.

We have to admit to never seeing anything like [Charles Ouweland]’s Van Der Heem 9908 electronic counter before. The Netherlands-based company, which was later acquired by Philips, built this six-digit, 1-MHz counter sometime in the 1950s. The display uses six separate edge-mounted panel meters numbered 0 through 9 to show the frequency of the incoming signal. The video below has a demo of what the instrument can do; we don’t know if it was restored at some point, but it still works and it’s actually pretty accurate. Later in the video, he gives a tour of the insides, which is the real treat — the case opens like a briefcase and contains over 20 separate PCBs with a bunch of germanium transistors, all stitched together with point-to-point wiring.

We appreciate the look inside this unique piece of test equipment history. It almost seems like something that would have been on the bench while this Apollo-era IO tester was being prototyped.

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Teardown: Verizon AC791L Jetpack 4G Mobile Hotspot

December 14, 2021 by 24 Comments

The saying “time and tide wait for no man” is usually used as a verbal kick in the pants, a reminder that sometimes an opportunity must be seized quickly before it passes by. But it can also be interpreted as a warning about the perpetual march of time and how it impacts the world around us. In that case, we would do well to add cellular technology to the list of proverbial things that wait for no one. Do you need 5G? No. Do you want it? Probably not. But it’s here, so be a good consumer and dump all your 4G hardware in the name of technical progress.

This line of logic may explain how the Verizon-branded Netgear AC791L 4G “Jetpack” hotspot you see here, despite being in perfect working order, found itself in the trash. The onset of 5G must have been particularly quick for the previous owner, since they didn’t even bother to wipe their configuration information from the device. In the name of journalistic integrity I won’t divulge the previous owner’s identity; but I will say that their endearing choice of WPA2 key, iluvphysics, makes for a nice fit with our publication.

A quick check of eBay shows these devices, and ones like it, are in ample supply. At the time of this writing, there were more than 1,500 auctions matching the search term “Verizon jetpack”, with most of them going for between $20 and $50 USD. We like cheap and easily obtainable gadgets that can be hacked, but is there anything inside one of these hotspots that we can actually use? Let’s find out.

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[Kerry Wong] Is Really Into Scope Meters

December 12, 2021 by 13 Comments

If a combination multimeter and oscilloscope is on your holiday shopping list this year, you might want to have a look at some of [Kerry Wong’s] recent videos on the subject. Over several videos he looks at — inside and out — an OWON HDS272S and a Hantek 2D72, both reasonably inexpensive entries in the field. Both instruments are similar and have a few variants depending on the frequency capability and the addition of a waveform generator.

There are several videos on the Hantek device that are a few months old, then some recent videos — like the one below — on the OWON device along with some comparison videos.

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Teardown: Analog Radionic Analyzer

November 9, 2021 by 67 Comments

Have you ever looked up a recipe online, and before you got to the ingredients, you had to scroll through somebody’s meandering life story? You just want to know how many cans of tomato paste to buy, but instead you’re reading about cozy winter nights at grandma’s house? Well, that’s where you are right now, friend. Except instead of wanting to know what goes in a lasagna, you just want to see the inside of some weirdo alternative medicine gadget. I get it, and wouldn’t blame you for skipping ahead, but I would be remiss to start this month’s teardown without a bit of explanation as to how it came into my possession.

So if you’ll indulge me for a moment, I’ll tell you a story about an exceptionally generous patron, and the incredible wealth of sham medical hokum that they have bestowed upon the Hackaday community…

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Heathkit IM-13 VTVM Repair

November 7, 2021 by 16 Comments

If you are under a certain age, you might not know the initialism VTVM. It stands for vacuum tube voltmeter. At first glance, you might just think that was shorthand for “old voltmeter” but, in fact, a VTVM filled a vital role in the old days of measuring instruments. [The Radio Mechanic] takes us inside a Heathkit IM-13 that needed some loving, and for its day it was an impressive little instrument.

Today, our meters almost always have a FET front end and probably uses a MOSFET. That means the voltage measurement probes don’t really connect to the meter at all. In a properly working MOSFET, the DC resistance between the gate and the rest of the circuit is practically infinite. It is more likely that a very large resistor (like 10 megaohms) is setting the input impedance because the gate by itself could pick up electrostatic voltage that might destroy the device. A high resistance like that is great when you make measurements because it is very unlikely to disturb the circuit you are trying to measure and it leads to more accurate measurements.

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