Ruined 1993 ThinkPad Tablet Brought Back From The Brink

November 18, 2024 by 10 Comments

Collecting retrocomputers is fun, especially when you find fully-functional examples that you can plug in, switch on, and start playing with. Meanwhile, others prefer to find the damaged examples and nurse them back to health. [polymatt] can count himself in that category, as evidenced by his heroic rescue of an 1993 IBM ThinkPad Tablet.

The tablet came to [polymatt] in truly awful condition. Having been dropped at least once, the LCD screen was cracked, the case battered, and all the plastics were very much the worse for wear. Many of us would consider it too far gone, especially considering that replacement parts for such an item are virtually unobtainable. And yet, [polymatt] took on the challenge nonetheless.

Despite its condition, there were some signs of life in the machine. The pen-based touch display seemed to respond to the pen itself, and the backlight sort of worked, too. Still, with the LCD so badly damaged, it had to be replaced. Boggling the mind, [polymatt] was actually able to find a 9.4″ dual-scan monochrome LCD that was close enough to sort-of fit, size-wise. To make it work, though, it needed a completely custom mount to fit with the original case and electromagnetic digitizes sheet. From there, there was plenty more to do—recapping, recabling, fixing the batteries, and repairing the enclosure including a fresh set of nice decals.

The fact is, 1993 IBM ThinkPad Tablets just don’t come along every day. These rare specimens are absolutely worth this sort of heroic restoration effort if you do happen to score one on the retro market. Video after the break.

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Analog Shift Register Revealed

November 17, 2024 by 18 Comments

Nowadays, if you want to delay an audio signal for, say, an echo or a reverb, you’d probably just do it digitally. But it wasn’t long ago that wasn’t a realistic option. Some devices used mechanical means, but there were also ICs like the TCA350 “bucket brigade” device that [10maurycy10] shows us in a recent post.

In this case, bucket brigade is a euphemism calling to mind how firemen would pass buckets down the line to put out a fire. It’s a bit of an analog analogy. The “bucket” is a MOSFET and capacitor. The “water” is electrical charge stored in the cap.  All those charges are tiny snippets of an analog signal.

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Completing The UE1’s Paper Tape Reader And First Squiggles

November 17, 2024 by 1 Comment
The UE1 tape reader in its nearly finished glory. Note the resistor to regulate the motor speed. (Credit: David Lovett, Usage Electric)
The UE1 tape reader in its nearly finished glory. Note the resistor to regulate the motor speed. (Credit: David Lovett, Usagi Electric)

On today’s installment of UE1 vacuum tube computer construction, we join [David Lovett] once more on the Usagi Electric farm, as he determines just how much work remains before the project can be called done. When we last left off, the paper tape reader had been motorized, with the paper tape being pulled through smoothly in front of the photodiodes. This left [David] with the task to create a PCB to wire up these photodiodes, put an amplification circuit together (with tubes, of course) to amplify the signal from said photodiodes, and add some lighting (two 1-watt incandescents) to shine through the paper tape holes. All of this is now in place, but does it work?

The answer here is a definite kinda, as although there are definitely lovely squiggles on the oscilloscope, bit 0 turns out to be missing in action. This shouldn’t have come as a major surprise, as one of the problems that Bendix engineers dealt with back in the 1950s was effectively the same one: they, too, use the 9th hole on the 8-bit tape as a clock signal, but with this whole being much smaller than the other holes, this means not enough light passes through to activate the photodiode.

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Hackaday Links: November 17, 2024

November 17, 2024 by 18 Comments

A couple of weeks back, we covered an interesting method for prototyping PCBs using a modified CNC mill to 3D print solder onto a blank FR4 substrate. The video showing this process generated a lot of interest and no fewer than 20 tips to the Hackaday tips line, which continued to come in dribs and drabs this week. In a world where low-cost, fast-turn PCB fabs exist, the amount of effort that went into this method makes little sense, and readers certainly made that known in the comments section. Given that the blokes who pulled this off are gearheads with no hobby electronics background, it kind of made their approach a little more understandable, but it still left a ton of practical questions about how they pulled it off. And now a new video from the aptly named Bad Obsession Motorsports attempts to explain what went on behind the scenes.

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The GREMLIN sensor suite contains several sensing modalities to detect, track, characterize and identify UAP in areas of interest. (Credit: US AARO)

US’s UFO-Hunting Aerial Surveillance System Detailed In Report

November 17, 2024 by 16 Comments

Formerly known as Unidentified Flying Objects, Unidentified Anomalous Phenomena (UAP) is a category of observations that are exactly what the UAP label suggests. This topic concerns the US military very much, as a big part of national security involves knowing everything that appears in the skies. This is the reason for the development of a new sensor suite by the Pentagon called GREMLIN. Recently, a new report has provided more details about what this system actually does.

Managed by the All-domain Anomaly Resolution Office (AARO) within the DoD, GREMLIN blends many different sensors, ranging from radar to ADS-B and RF monitors, together to establish a baseline and capture any anomalies within the 90-day monitoring period to characterize them.

UAPs were a popular topic even before the 1950s when people began to see them everywhere. Usually taking the form of lights or fast-moving objects in the sky, most UAP reports can be readily classified as weather balloons, satellites like Starlink, airplanes, the Northern Lights, the ISS, or planets like Mars and Venus. There are also curious phenomena such as the Hessdalen lights, which appear to be a geological, piezoelectric phenomenon, though our understanding of such natural lighting phenomena remains limited.

But it is never aliens, that’s one thing we know for sure. Not that UFO’s don’t exist. Really.

Schooling ChatGPT On Antenna Theory Misconceptions

November 17, 2024 by 39 Comments

We’re not very far into the AI revolution at this point, but we’re far enough to know not to trust AI implicitly. If you accept what ChatGPT or any of the other AI chatbots have to say at face value, you might just embarrass yourself. Or worse, you might make a mistake designing your next antenna.

We’ll explain. [Gregg Messenger (VE6WO)] asked a seemingly simple question about antenna theory: Does an impedance mismatch between the antenna and a coaxial feedline result in common-mode current on the coax shield? It’s an important practical matter, as any ham who has had the painful experience of “RF in the shack” can tell you. They also will likely tell you that common-mode current on the shield is caused by an unbalanced antenna system, not an impedance mismatch. But when [Gregg] asked Google Gemini and ChatGPT that question, the answer came back that impedance mismatch can cause current flow on the shield. So who’s right?

In the first video below, [Gregg] built a simulated ham shack using a 100-MHz signal generator and a length of coaxial feedline. Using a toroidal ferrite core with a couple of turns of magnet wire and a capacitor as a current probe for his oscilloscope, he was unable to find a trace of the signal on the shield even if the feedline was unterminated, which produces the impedance mismatch that the chatbots thought would spell doom. To bring the point home, [Gregg] created another test setup in the second video, this time using a pair of telescoping whip antennas to stand in for a dipole antenna. With the coax connected directly to the dipole, which creates an unbalanced system, he measured a current on the feedline, which got worse when he further unbalanced the system by removing one of the legs. Adding a balun between the feedline and the antenna, which shifts the phase on each leg of the antenna 180° apart, cured the problem.

We found these demonstrations quite useful. It’s always good to see someone taking a chatbot to task over myths and common misperceptions. We look into baluns now and again. Or even ununs.

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ESP32 Hosts A USB Keyboard In This Typewriter

November 17, 2024 by 12 Comments

Did you know the ESP32 can be a USB host? Well it can, and [Volos] uses host mode to build this fun little word processor.

The venerable ESP32 has a well-known USB device mode. Anyone who has programmed one has used it. A bit less known is the microcontroller’s ability to host USB devices. These days, operating as a USB device is relatively simple. But acting as a host is a much more complex task. The ESP32 has a software host that works — but only for Human Interface Devices (HID).  Human interface devices generally are keyboards, mice, trackballs, and similar devices that handle data relatively slowly, forming the interface with us simple humans.

[Volos] uses the EspUsbHost Arduino library for this project. The library makes USB host mode simple to use. Another piece of the puzzle is the LCD board [Volos] picked. It has a dual-role USB Type-C port, meaning the hardware to switch roles is baked in. Other boards may require some modifications or special cables to make things work.

The software is the best part of this build. [Volos] implemented a simple word processor. It can save and load files from a microSD card and, of course, edit text — all controlled by a USB keyboard. He had to use a 4-bit palette to save memory. This gives the device a retro charm that reminds us of Don Lancaster’s TV Typewriter. The source for this and all of [Volos] projects can be found on GitHub. Now, all we need is a spell check that can fit in the memory constraints of the ESP32! We have to admit the chip has a lot of potential USB tricks.

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