Mysterious Files PH

For some of us, the Speak ‘n Spell evokes pleasant memories of childhood as our first computer, along with one of those Merlin things. For others, it’s the ultimate circuit bending victim. For [Jeremy Geppert], they’re all-around good fun and he wanted to immortalize the device in a Simple Add-On (SAO).

This is [Jeremy]’s first board and SAO rolled into one, motivated by both Supercon and the SAO Contest. To start things off, [Jeremy] scaled down the design we all know and love to fit a 128×32 OLED display, and it looks great. The plan is to have the display, an amplified speaker, and a single button for input.

Before committing the board order, [Jeremy] had a brief freak-out about the pin distance as it relates to the window for the OLED display. Luckily, his brother suggested checking things first by printing a 1:1 scale image of the board outline, and laying that over the display.

This is the week it all comes together, as the tiny switches and (regular-size) connectors have arrived, and the boards are due quite soon. Go, [Jeremy], go!

It is hard to imagine that a handful of decades ago, TV wasn’t a thing. We’ve talked a few times about the birth of television. After an admittedly slow slow start, it took over like wildfire. Of course, anything that sells millions will spawn accessories. Some may be great. Then there are others.

We wanted to take a nostalgic look back at some of the strange add-ons people used to put on or in their TVs. Sure, VCRs, DVD players, and video game consoles were popular. But we were thinking a little more obscure than that.

Rabbit Ears

Every once in a while, we see an ad or a box in a store touting the ability to get great TV programming for free. Invariably, it is a USB device that lets you watch free streaming channels or it is an antenna. There was a time when nearly all TVs had “rabbit ears” — so called because they made an inverted V on the top of your set.

These dipoles were telescoping and you were supposed to adjust them to fit the TV station you were watching but everyone “knew” that you wanted them as long as possible at all times. Holding one end of them gave it a ground and would give you a major improvement in picture. People also liked to wrap tin foil around the tips. Was it like a capacitive hat? We aren’t sure.

The better rabbit ears had knobs and switches along with multiple elements. If you lived close to a TV station, you probably didn’t need much. If you didn’t, no number of fancy add-ons would likely help you.

External Antenna with Rotator

If you really wanted to get TV from a distance, you needed an outside antenna. Most of these were either yagi or log periodic designs. That means they were very directional. The also means you probably needed a way to rotate it. If you were lucky, all the TV stations were in the same direction from you. Then you didn’t need to rotate your antenna. Some UHF-only antennas looked like dishes and they, too, were directional.

Rotators were crazy. They were all a little different, but typically you’d move a big knob to the direction you wanted the antenna pointing. Then you’d hear CHUNK, CHUNK, CHUNK as the antenna actually moved. This was a cheap form of stepper motor. Some rotators used something akin to a selsyn to move continuously, but most just moved to a few dozen points around a circle. Hams still use modern versions of antenna rotators to adjust directional antennas.

CRT Brightener

The most expensive part of any old TV was the picture tube. These tubes were fragile and expensive to make and ship, so it was often the case that if the ‘tube went out, it was cheaper to just buy a new TV.

When a picture tube started to go dark, you could sometimes run a high voltage through it to restore it (you being a TV repairman with the equipment to do it). Or, you could try installing a CRT brightener. These devices looked a little like tubes. You’d remove the connector from the CRT’s neck and install the device. Then, the wire that used to plug into the CRT would plug into the other side of the device.

These were essentially little transformers that boosted the AC voltage going to the filaments. They worked for a while, but it probably meant a new TV wasn’t far in your future. If you want to know more than you could possibly imagine about how these work, there was an article in Radio Electronics written by someone who worked for a company that made them, and it goes into incredible detail. [Chris] shows us a 1950s TV that had one of these in it. You could actually stack these one on top the other if you wanted to take your chances and try to keep the old TV working as long as possible.

Ghost Eliminator

According to a Layfayette Electronics catalog the Rembrandt TV Ghost Eliminator “Electrically rotates the polar-receiving pattern of your existing antenna and phases the ground wave picked up by the electrical wiring system with the sky wave picked up by the antenna.” What?

As far as we can tell, these units were just attenuators, which reduced weaker signals below the receiver’s ability to find them.

Tuner Rebuild and Cleaners

One of the key components of a TV was the tuner. Because of the high frequencies and the low technology of the day, these were usually a compact unit that was directly behind the knob you used to change channels. The output of the tuner was relatively a low-frequency signal at the intermediate frequency, and that’s what the rest of the TV used.

It was difficult to make broadband devices back then, so the tuners usually had banks of tuned circuits, and a giant mechanical switch selected the ones you wanted. That’s why you turned the knob to pick the channel you wanted. With contacts like that, they eventually get dirty. Contact cleaners for tuners were common and probably contained a lot of things you aren’t allowed to put in spray cans today. Tun-O-Foam was one common brand.

But if you really had trouble with your tuner, you could pull it out and send it to one of the many companies that would clean and service it for a low price. For a little more, you could buy a refurbished tuner from the same people. They’d always advertise a low price but note that tubes, transistors, and diodes were charged “at cost.” Shipping, too, usually. The reality is that most tuners probably needed a good cleaning and, perhaps, a realignment.

Tube Testers/Tube Guard

You’ve probably heard us talk about tube testers before. One thing that is the enemy of tubes is inrush current. A cold filament draws more current than a hot filament, so tubes get a big jolt of current while they are warming up. The “Tube Guard” was a device you plugged into the wall and then plugged the TV into it. It would prevent fast inrush current. Maybe that would save you a trip to the tube tester at the local drugstore.

You could go into many drugstores and other retail places and find a tube tester. There was usually a book or some other way to look up your tube. The book would tell you to put in socket #8 and set switch 1 to F, switch 2 to A, and so on. Then you’d push a button and big meter would move a needle to a green region if the tube was good or a red region if it was bad. Of course, that wasn’t foolproof, but it did work much of the time since tubes have common failure modes.

If the tube was bad, you’d open the bottom of the tester, find the replacement tube and take it to the register. There were also portable units that service people might carry, like the one in the video below. Like many of the meters, it didn’t have a book, but it had a scroll that you would roll to find the right settings. However, a typical retail store tube tester was usually easier to use than these specialized units.

That’s Not All

There are plenty of other TV gadgets. We mentioned the old VCRs, DVDs, and video games, of course. But there were also color wheels, magnifying screens and more. We’ve even seen boxes that claim to convert your TV into a video phone.

You could get a box that would censor swear words. You could even get pay TV in the 1960s if you were willing to put coins into your set.

Many of the images in this post are from scans of old magazines and catalogs from the World Radio History site. A great resource if you enjoy looking at the way things were. The featured image, however, is a still of “1950s TV set“, a 3D model by [Kathrin&Christian].

This week, Hackaday Editors Elliot Williams and Tom Nardi start things off by acknowledging an incredible milestone: 20 years of Hackaday! Well, probably. When a website gets to be this old, it’s a little hard to nail down when exactly things kicked off, but it seems like September of 2004 is about right. They’ll also go over the latest updates for the fast-approaching Hackaday Supercon, and announce the winner of another tough What’s That Sound challenge.

From there, the conversation makes its way from the fascinating electrically-activated adhesive holding the latest iPhone together to pulsed-power lasers and a high flying autonomous glider designed and built by a teenager. You’ll also hear about 3D printing on acrylic, home biohacking, and the Tiny Tool Kit Manifesto. Stick around to the end to hear the duo discuss the fine art of good documentation, and an incredible bodge job from Arya Voronova.

Check out the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Download in DRM-free MP3 and savor at your leisure.

Episode 290 Show Notes:

News:

• Hackaday Turns 20-ish!
  • Hackaday Celebrates 15 years!
• 2024 Hackaday Superconference Speakers, Round Two

What’s that Sound?

• Congrats to [Davip] for getting a punch-tape reader/writer right.

Interesting Hacks of the Week:

• Find My Power Tool Battery
  • GitHub – seemoo-lab/openhaystack
  • GitHub – JJTech0130/pypush:Cross-platform iMessage POC
• Hands-on With New IPhone’s Electrically-Released Adhesive
  • Apple May Use Electrical Debonding For Battery Replacement
• Most Powerful Laser Diodes, Now More Powerful
  • A Quickly-Hacked-Together Avalanche Pulse Generator
  • Avalanche Pulse Generator Build Using 2N3904 – Kerry D. Wong
• Winamp Releases Source Code, But Is It Really Open?
• 3D Printing On Top Of Laser Cut Acrylic
  • 3D Printing Wearables With A Net
• StratoSoar Glider Flies Itself From High Altitude

Quick Hacks:

• Elliot’s Picks:
  • ESP32 Powers Custom Darkroom Timer
  • Little Pharma On The Prairie
  • Custom Mini-Neon Signs In 10 Minutes
• Tom’s Picks:
  • Reviving A 15-Year Old Asus EeePC With Modern MX Linux
  • Brass Propeller Gets Impressive Hand Trimming
  • The Tiny Toolkit Manifesto

Can’t-Miss Articles:

• Supercon 2023: The Road To Writing Great Step-by-Step Instructions
• Switching Regulators: Mistake Fixing For Dummies

At the risk of stating the obvious, building big things can be difficult. Sure, parts that fit on the bed of a 3D printer are easy to make, if not particularly fast, and scaling up from there is possible. But if you need a long beam or structural element, printing makes little sense; better to buy than build in that case. The trouble then becomes, how do you attach such parts together?

Enter Makerpipe. This South Carolina company, recently out of a crowdfunding campaign, makes a range of structural connectors and fittings for electrical mechanical tubing, or EMT, the galvanized steel conduit used in the electrical trades. EMT is widely available in multiple sizes and is relatively cheap, although we have noticed that the price here has ticked up quite a bit over the last couple of years. It also has the advantage of being available off-the-shelf at any big-box home improvement store, meaning you have instant access to a fantastic building material.

Makerpipe’s bolt-together couplings let you turn pieces of EMT, easily cut with a hacksaw or pipe cutter, into structures without the need for welding. Yes, you can do the same with extruded aluminum, but even if you’re lucky enough to live near a supply house that carries extrusions and the necessary fittings and is open on Saturday afternoon, you’ll probably pay through the nose for it.

Makerpipe isn’t giving their stuff away, and while we normally don’t like to feature strictly commercial products, something that makes building large structures easier and faster seems worth sharing with our community. We’ve done our share of fabricobbling together EMT structures after all, and would have killed for fittings like these.

If you need an amplifier, [Hans Rosenberg] has some advice. Don’t design your own; grab cheap and tiny RF amplifier modules and put them on a PCB that fits your needs. These are the grandchildren of the old mini circuits modules that were popular among hams and RF experimenters decades ago. However, these are cheap, simple, and tiny.

You only need a handful of components to make them work, and [Hans] shows you how to make the selection and what you need to think about when laying out the PC board. Check out the video below for a very detailed deep dive.

To get the best performance, the PCB layout is at least as important as the components. [Hans] shows what’s important and how to best work out what you need using some online calculators.

Using a NanoVNA and a USB spectrum analyzer, [Hans] makes some measurements on the devices using different components, which is very instructive. The measurements lined up fairly well with the theory, and you can see the effects of changing key components in the design.

[Hans] has a lot to say about RF PCB design. If you want to get into a lot of details, don’t forget to check out [Michael Ossmann’s] Supercon workshop on RF design.

While Texas Instruments maintains dominance in the calculator market (especially graphing calculators), there was a time when this wasn’t the case. HP famously built the first portable scientific calculator, the HP-35, although its reverse-Polish notation (RPN) might be a bit of a head-scratcher to those of us who came up in the TI world of the last three or four decades. Part of the reason TI is so dominant now is because they were the first to popularize infix notation, making the math on the calculator look much more like the math written on the page, especially when compared to the RPN used by HP calculators. But if you want to step into a time machine and see what that world was like without having to find a working HP-35, take a look at [Jeroen]’s DIY RPN calculator.

Since the calculator is going to be RPN-based, it needs to have a classic feel. For that, mechanical keyboard keys are used for the calculator buttons with a custom case to hold it all together. It uses two rows of seven-segment displays to show the current operation and the results. Programming the Arduino Nano to work as an RPN calculator involved a few tricks, though. [Jeroen] wanted a backspace button, but this disrupts the way that the Arduino handles the input and shows it on the display but it turns out there’s an Arudino library which solves some of these common problems with RPN builds like this.

One of the main reasons that RPN exists at all is that it is much easier for the processor in the calculator to understand the operations, even if it makes it a little bit harder for the human. This is because early calculators made much more overt use of a stack for performing operations in a similar way to Assembly language. Rather than learning Assembly, an RPN build like this can be a great introduction to this concept. If you want to get into the weeds of Assembly programming this is a great place to go to get started.

YouTuber The Science Furry has been attempting to make a split-anode magnetron and, after earlier failures, is having another crack at it. This also failed, but they’ve learned where to focus their efforts for the future, and it sure is fun to follow along.

The magnetron theory is simple enough, and we’ve covered this many times, but the split anode arrangement differs slightly from the microwave in your kitchen. The idea is to make a heated filament the cathode, so electrons are ejected from the hot surface by thermionic emission. These are forced into a spiral path using a perpendicular magnetic field. This is a result of the Lorentz force. A simple pair of magnets external to the tube is all that is needed for that. Depending on the diameter of the cavity and the gap width, a standing wave will be emitted. The anodes must be supplied with an alternating potential for this arrangement to work. This causes the electrons to ‘bunch up’ as they cross the gaps, producing the required RF oscillation. The split electrodes also allow an inductor to be added to tune the frequency of this standing wave. That is what makes this special.

The construction starts with pre-made end seals with the tungsten wire electrode wire passing through. In the first video, they attempted to coat the cathode with barium nitrate, but this flaked off, ruining the tube. The second attempt replaces the coiled filament with a straight wire and uses a coating paste made from Barium Carbonate mixed with nitrocellulose in a bit of acetone. When heated, the nitrocellulose and the carbonate will decompose, hopefully leaving the barium coating intact. After inserting the electrode assembly into a section of a test tube and welding on the ends, the vacuum could be pulled and sealed off. After preheating the cathode, some gasses will be emitted into the vacuum, which is then adsorbed into a nearby titanium wire getter. At least, that’s the theory.

Upon testing, this second version burned out early on for an unknown reason, so they tried again, this time with an uncoated cathode. Measuring the emission current showed only 50 uA, which is nowhere near enough, and making the filament this hot caused it to boil off and coat the tube! They decide that perhaps this is one step too many and need to experiment with the barium coating by making simpler diode tubes to get the hang of the process!

If this stuff is over your head, you need a quick history lesson about the magnetron. Next check out this teardown. Finally, we have covered DIY magnetrons before, like this excellent DIY magnetron-powered plasma sputtering device. Yes, you read that correctly.

Thanks to [Kelvin Ly] for the tip!