crt

147 Articles

Unique Flat-Screen Display Put To Use In CRT Game Boy

November 13, 2018 by 30 Comments

The cathode-ray tube ruled the display world from the earliest days of TV until only comparatively recently, when flat-screen technology began to take over. CRTs just kept getting bigger over that time until they reached a limit beyond which the tubes got just too bulky to be practical.

But there was action at the low end of the CRT market, too. Tiny CRTs popped up in all sorts of products, from camcorders to the famous Sony Watchman. One nifty CRT from this group, a flat(tish) tube from a video intercom system, ended up in [bitluni]’s lab, where he’s in the process of turning it into a retro Game Boy clone with a CRT display. The display, which once showed the video from a door-mounted camera, was a gift from a viewer. Date codes on the display show it’s a surprisingly recent device; were monochrome TFT displays that hard to come by in 2007? Regardless, it’s a neat design, with the electron gun shooting upward toward a curved phosphor screen. With a little Google-assisted reverse engineering, [Bitluni] was able to track done the video connections needed to use his retro game console, which uses an ESP32 that outputs composite video. He harvested the intercom speaker for game audio, added a temporary Nintendo gamepad, and soon he was playing Tetris in glorious monochrome on the flat screen.

The video below is only the first in a series where the prototype will be stuffed into one nice tidy package. It certainly still needs some tweaking, but it’s off to a great start. We can’t wait to see the finished product.

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Circuit Bending A TV For Better Input

October 15, 2018 by 55 Comments

If you haven’t noticed, CRTs are getting hard to find. You can’t get them in Goodwill, because thrift stores don’t take giant tube TVs anymore. You can’t find them on the curb set out for the trash man, because they won’t pick them up. It’s hard to find them on eBay, because no one wants to ship them. That’s a shame, because the best way to enjoy old retrocomputers and game systems is with a CRT with RGB input. If you don’t already have one, the best you can hope for is an old CRT with a composite input.

But there’s a way. [The 8-Bit Guy] just opened up late 90s CRT TV and modded it to accept RGB input. That’s a monitor for your Apple, your Commodore, and a much better display for your Sega Genesis.

There are a few things to know before cracking open an old CRT and messing with the circuits. Every (color) CRT has three electron guns, one each for red, green, and blue. These require high voltage, and in CRTs with RGB inputs you’re looking at a circuit path that takes those inputs, amplifies them, and sends them to the gun. If the TV only has a composite input, there’s a bit of circuitry that takes that composite signal apart and sends it to the guns. In [8-bit guy]’s TV — and just about every CRT TV you would find from the mid to late 90s — there’s a ‘Jungle IC’ that handles this conversion, and most of the time there’s RGB inputs meant for the on-screen display. By simply tapping into those inputs, you can add RGB inputs with fancy-schmancy RCA jacks on the back.

While the actual process of adding RGB inputs to a late 90’s CRT will be slightly different for each individual make and model, the process is pretty much the same. It’s really just a little bit of soldering and then sitting back and playing with old computers that are finally displaying the right colors on a proper screen.

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This Nearly NIMO Clock Fakes It And Makes It

September 16, 2018 by 12 Comments

Pity the aficionado of rare vintage displays. While Nixies and VFD tubes get all the attention and benefit from a thriving market to satisfy demand, the rarer displays from the mid-20th century period are getting harder and harder to find. One copy of an especially rare display is hard enough to find. Six copies for a clock? That’s a tall order.

That doesn’t mean you can’t fudge it, though, which is how this faux-NIMO clock came to be. [Paul Bricmont] was inspired by [Fran Blanche]’s NIMO tube primer, wherein the rare, single-digit CRT display was put through its paces. We’ve got to admit, it’s an easy display to fall in love with, thanks to its eerie blue phosphor glow, high voltage supply, and general quirkiness. [Paul] was unable to lay hands on a single tube, though, so he faked it with six tiny TFT displays and some plastic lenses. The lenses mimic the curved front glass of the original NIMO, while the TFT displays provide the stencil-style images of each numeral. The phosphor glow comes from replacing the stock white TFT backlight with a Neopixel array that can produce just the right shade of blue-green. 3D-printed modules hold two digits each, and the usual Arduino components run the show. The effect is quite convincing, although we bet some software tweaks could add things like faux burn-in and perhaps soften the edges of the digits to really sell it.

What other rare displays could be replicated this way? Given the variety of displays that were tried in the pre-LED era, it may be a rich vein to mine.

A Look At The Smallest Magnetic Deflection CRT Ever Made

September 15, 2018 by 40 Comments

A high-resolution LCD or OLED screen is a commodity component that we can buy on a little breakout board and plug into our microcontrollers without spending more than a dollar or two. We can buy them in sizes ranging from sub-postage-stamp to desktop TV if our budgets stretch that far, and they are easy to drive in every sense of the word. It is not so long ago though that a high-resolution LCD, even a small one, was a seriously expensive component. In consumer electronic devices such as camcorders engineers went to great lengths to avoid those costs, and [12voltvids] recently took a look at one of them.

Inside the viewfinder of a miniaturized Sony camcorder is a CRT. It’s fairly mundane in the scheme of CRTs, in that it’s a monochrome device with no unexpected features. Except that is, for one thing. It’s tiny, with only a 0.5″ inch screen size. Everything else is the same as your vintage full-sized TV, it has an electron gun and a deflection and focusing coil pack, but the entire device has been miniaturized to the point at which the coil pack is larger than the screen it is driving. On the accompanying PCB are all the support circuits, including a tiny flyback transformer and a single IC –  a Rohm BA7149 electronic viewfinder driver that is as near as possible an entire CRT TV on a chip. That’s it, the whole device runs from a single 5 volt supply.

He doesn’t give the date of the camcorder, but given that it looks as though it uses 8mm cassette tapes and has a curved miniaturized design rather than the angular black exteriors that were fashionable earlier we’d guess it to be from some time around the year 2000. To give it some context, at the time one of the hottest pieces of consumer electronics would have been a Diamond Rio MP3 player, and if your desktop PC had the first of the AMD Athlon processors you probably considered it to be about the fastest you could hope to own. The surprise then is that Sony still considered it more economical even at that point to use the CRT and associated circuitry than a tiny LCD. Either way we’d agree with him that it’s a keeper, a fascinating curio for any electronics enthusiast. If we see an old camcorder going for not a lot, we’ll certainly give it a second look after this.

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The Pre-CRT Oscilloscope

September 11, 2018 by 31 Comments

Oscilloscopes are especially magical because they translate the abstract world of electronics into something you can visualize. These days, a scope is likely to use an LCD or another kind of flat electronic display, but the gold standard for many years was the ubiquitous CRT (cathode ray tube). Historically, though, CRTs were not very common in the early days of electronics and radio. What we think of as a CRT didn’t really show up until 1931, although if you could draw a high vacuum and provide 30 kV, there were tubes as early as 1919. But there was a lot of electronics work done well before that, so how did early scientists visualize electric current? You might think the answer is “they didn’t,” but that’s not true. We are spoiled today with high-resolution electronic displays, but our grandfathers were clever and used what they had to visualize electronics.

Keep in mind, you couldn’t even get an electronic amplifier until the early 1900s (something we’ve talked about before). The earliest way to get a visual idea of what was happening in a circuit was purely a manual process. You would make measurements and draw your readings on a piece of graph paper.

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Need A Tiny CRT? Karaoke Might Just Help

July 31, 2018 by 30 Comments

[Brett] is working on a video installation, and for the past few months, has been trying to get his hands on tiny CRTs any way he can. After initially coming up short, he happened across a karaoke machine from 2005, and got down to work.

Karaoke machines of this vintage are typically fairly low-rent affairs, built cheaply on simple PCBs. [Brett] found that the unit in question was easy to disassemble, having various modules on separate PCBs joined together with ribbon cables and headers. However, such machines rarely have video inputs, as they’re really only designed to display low-res graphics from CD-G format discs.

While investigating the machine, initial research online proved fruitless. In the end, a close look at the board revealed just what [Brett] was looking for – a pin labeled video in! After throwing in a Raspberry Pi Zero and soldering up the composite output to the karaoke machine’s input pin, the screen sprung to life first time! This initial success was followed by installing a Raspberry Pi 3 for more grunt, combined with a Screenly install – and a TRS adapter the likes of which we’ve never seen before. This allows video to be easily pushed to the device remotely over WiFi. [Brett] promises us there is more to come.

Karaoke is a sparse topic in the Hackaday archives, but we’ve seen a couple builds, like this vocal processor. If you’ve got the hacks, though? You know where to send ’em.

Raytheon’s Analog Read-Only Memory Is Tube-Based

June 18, 2018 by 8 Comments

There are many ways of storing data in a computer’s memory, and not all of them allow the computer to write to it. For older equipment, this was often a physical limitation to the hardware itself. It’s easier and cheaper for some memory to be read-only, but if you go back really far you reach a time before even ROMs were widespread. One fascinating memory scheme is this example using a vacuum tube that stores the characters needed for a display.

[eric] over at TubeTime recently came across a Raytheon monoscope from days of yore and started figuring out how it works. The device is essentially a character display in an oscilloscope-like CRT package, but the way that it displays the characters is an interesting walk through history. The monoscope has two circuits, one which selects the character and the other determines the position on the screen. Each circuit is fed a delightfully analog sine wave, which allows the device to create essentially a scanning pattern on the screen for refreshing the display.

[eric] goes into a lot of detail on how this c.1967 device works, and it’s interesting to see how engineers were able to get working memory with their relatively limited toolset. One of the nice things about working in the analog world, though, is that it’s relatively easy to figure out how things work and start using them for all kinds of other purposes, like old analog UHF TV tuners.