Author: Al Williams

4537 Articles

Retrotechtacular: Color TV

November 12, 2024 by 21 Comments

We have often wondered if people dreamed in black and white before the advent of photography. While color pictures eventually became the norm, black and white TV was common for many years. After all, a TV set was a big investment, so people didn’t run out and buy the latest TV every year. Even if you did buy a new or used TV, a black and white model was much less expensive and, for many years, some shows were in black and white anyway. RCA, of course, wanted you to buy a color set. [PeriscopeFilm] has a 1963 promotional film from RCA extolling the virtues of a color set. The video also shows something about how the sets were made, as you can see below.

We aren’t sure we’d have led with the idea that color could save your life in this context, but we have to salute the melodrama. There is a good bit of footage of picture tube manufacturing, although the technical detail is — understandably — aimed at the general public.

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Z80 Testing The 80s Way

November 12, 2024 by 24 Comments

According to [MTSI], if you used a Z80 chip back in the 1980s, it almost certainly passed through the sole Fairchild Sentry 610 system that gave it the seal of approval.

The Sentry was big iron for its day. The CPU was a 24-bit device and ran at a blistering 250 kHz. Along with a tape drive and a specialized test bed, it could test Z80s, F8s, and other Mostek products of the day. There was a disk drive, too. The 26-inch platters stored under 10 kilobytes. Despite the relatively low speed of the CPU, the Sentry could test devices running up to 10 MHz, which was plenty for the CPUs it was testing. The actual test interface ran at 11 MHz and used an exotic divider to generate slower frequencies.

According to the post, an informal count of the number of chips in the device came up with around 60,000. That, as you might expect, took a huge power supply, too.

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Retrogadgets: Oscilloscope Cameras

November 11, 2024 by 23 Comments

Today, if you want to get a picture from your oscilloscope — maybe to send to a collaborator or to stick in a document or blog post — it is super easy. You can push an image to a USB stick or sometimes even just use the scope’s PC or web interface to save the picture directly to your computer. Of course, if it is on the computer, you could use normal screen capture software. But that hasn’t always been the case. Back in the days when scopes were heavy and expensive, if you wanted to capture an image from the tube, you took a picture. While you might be able to hold up your camera to the screen, they made specific cameras just for this purpose.

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Cheap Sensor Changes Personality

November 10, 2024 by 27 Comments

If you want to add humidity and temperature sensors to your home automation sensor, you can — like [Maker’s Fun Duck] did — buy some generic ones for about a buck. For a dollar, you get a little square LCD with sensors and a button. You even get the battery. Can you reprogram the firmware to bend it to your will? As [Duck] shows in the video below, you can.

The device advertises some custom BLE services, but [Duck] didn’t want to use the vendor’s phone app, so he cracked the case open. Inside was a microcontroller with Bluetooth, an LCD driver, a sensor IC, and very little else.

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Component Tester Teardown

November 10, 2024 by 10 Comments

In the modern age, when you hear “component tester” you probably think of one of those cheap microcontroller-based devices that can identify components and provide basic measurements on an LCD screen. However, in the past, these were usually simple circuits that generated an XY scope plot. The trace would allow an experienced operator to identify components and read a few key parameters. [Thomas] tears down an old Hameg device that uses this principle in the video below.

The unit is in a nice enclosure and has a feature that controls the amount of current the unit uses in the excitation signal. It plugs into the wall, and you can connect the component under test with either test leads or a socket. The output, of course, is a pair of BNCs for the scope’s X and Y inputs.

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Building A DIY Nipkow Disk Display

November 10, 2024 by 28 Comments

Before flat screen technologies took over, we associate TV with the CRT. But there were other display technologies that worked, they just weren’t as practical. One scheme was the Nipkow disk, and [Bitluni] decided to build a working demonstration of how such a system works.

Essentially, there’s a spinning disk with a spiral pattern of holes in it. As the disk spins, a light behind it turns on or off. If you time everything right, you get an image that can move. This particular model uses stepper motors, which is a bit of a modern concession.

The result was actually much better than you might guess, but a far cry from a modern display device, of course. The screen material needed a little tweaking, but even the initial results were very impressive. If this were trying to be practical, it would probably require a bit more work on the light source and screen.

Interestingly, the Nipkow disk arrangement was just as suitable for scanning as displaying. Instead of a light behind the wheel, you simply used a light sensor. Of course, in practice, getting everything synchronized and mass-producing high-resolution sets would have been a tremendous challenge a century ago.

Not that people didn’t try. There were even color systems using mechanical wheels. In the 1930s, people were sure your TV would contain spinning disks.

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Inside An Arcade Joystick

November 9, 2024 by 6 Comments

If you ever played an arcade game and wondered what was inside that joystick you were gripping, [Big Clive] can save you some trouble. He picked up a cheap replacement joystick, which, as you might expect, has a bunch of microswitches. However, as you can see in the video below, there are some surprising features that make sense when you think about it.

For one, there are plates you can put on the bottom to limit the joystick’s travel depending on the game. That is, some games only want the stick to move up and down or left and right. The knobs are quite nice, and [Clive] mentions the size and thread of the knob with the idea you could use them in different applications. You can also buy replacement knobs if you don’t want to get the whole assembly.

The mechanics are rugged but straightforward. The circuit board is surprisingly stylish but also simple. Still interesting to see what’s inside one of these, even though the schematic is extremely simple.

If you need an excuse to use one of these, how about an arcade table? If you aren’t a woodworker, grab a 3D printer instead.

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