heathkit

31 Articles

Q Multiplier — Er… Multiplies Q

January 18, 2021 by 13 Comments

If you are below a certain age, you’ve probably never heard of a Q multiplier. This is a device that increases the “Q” of a radio receiver’s intermediate frequency and, thus, provide a higher selectivity. If you enjoy nostalgia, you can see inside a 1960s-era Heathkit QF-1 Q multiplier in [Jeff’s] informative video, below.

The Q multiplier was a regenerative amplifier that operated at just below the oscillation point. This provided very high amplification for the frequency of interest and less amplification for other frequencies. Some radios had a stage like this built-in, but the QF-1 was made to add into an external radio. For some Heathkit receivers, there was a direct plug to tap into the IF stage for this purpose. Othe radios would require some hacking to get it to work.

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Retro Computer Trainer Gets A Raspberry Pi Refit

October 12, 2020 by 11 Comments

We know what you’re thinking: this is yet another one of those “Gut the retro gear for its cool old case and then fill it up with IoT junk” projects. Well, rest assured that extending and enhancing this 1970s computer trainer is very much an exercise in respecting the original design, and while there’s a Pi inside,  it doesn’t come close to spoiling the retro goodness.

Like many of a similar vintage as [Scott M. Baker], the Heathkit catalog was perhaps only leafed through marginally less than the annual Radio Shack catalog. One particularly desirable Heathkit item was the ET-3400 microcomputer learning system, which was basically a 6800-based computer surrounded by a breadboarding area for experimentation. [Scott] got a hold of one of these, but without the optional expansion accessory that would allow it to do interesting things such as running BASIC or even supporting a serial port. So [Scott] decided to roll his own expansion board.

The expansion card that [Scott] designed is not strictly a faithful reproduction, at least in terms of the original BOM. He turned to more modern — and more readily available — components, but still managed to provide the serial port, cassette interface, and RAM/ROM expansion of the original unit. The Raspberry Pi is an optional add-on, which just allows him to connect wirelessly if he wants. The card fits into a 3D-printed case that sits below the ET-3400 and maintains the original trainer’s look and feel. The longish video below shows the build and gives a tour of the ET-3400, both before and after the mods.

It looks as though trainers like these and other artifacts from the early days of the PC revolution are getting quite collectible. Makes us wish we hadn’t thrown some things out.

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Antique Oscilloscope Gets New Home And Purpose

September 1, 2020 by 11 Comments

As the pace of technology charges blindly forward, a lot of older tools or products get left in the dust, forgotten to most but those left with them. This doesn’t mean they’re useless, though. In fact, old technology that continues to survive in the present tends to be more robust and sturdy than most modern, cheap replacements. While this might be survivorship bias, this is certainly true in particular of oscilloscopes. Rugged CRTs in large metal housings with discrete through-hole components in simple layouts made them reliable, but they’re heavy, bulky, and lack features of modern instruments. With some modifications, though, you can give them a new home and keep their vintage aesthetic.

[BuildComics] had just such an oscilloscope on hand and set out to make it into something useful but aesthetically pleasing as well. With a small circuit board, formerly available as a kit from Sparkfun/Dutchtronix but now only available if you can build them yourself, the cathode ray tube can be modified to output not waveforms but rather a working clock face. The donor oscilloscope was a Heathkit IO-102 which was fine for its time but is now lacking, so the CRT was removed from its housing and placed in a custom-built enclosure with a 40s radio style that suits its new purpose well.

Seeing old hardware that is past its prime being put to work in a new way is great, both from a technical standpoint and also because that’s usable hardware that’s being kept out of the landfill. Oscilloscopes are popular for projects like these too since they are relatively easy to understand and modify. Besides being used as clocks, we’ve also seen them modified to play video games such as Pac-Man.

Reliving Heathkit’s Glory Days Through A Teardown And Rebuild

June 26, 2020 by 10 Comments

In its heyday, the experience offered by the Heath Company was second to none. Every step of the way, from picking something out of the Heathkit catalog to unpacking all the parts to final assembly and testing, putting together a Heathkit project was as good as it got.

Sadly, those days are gone, and the few remaining unbuilt kits are firmly in the unobtanium realm. But that doesn’t mean you can’t tear down and completely rebuild a Heathkit project to get a little taste of what the original experience was like. [Paul Carbone] chose a T-3 Visual-Aural signal tracer, a common enough piece that’s easy to find on eBay at a price mere mortals can afford. His unit was in pretty good shape, especially for something that was probably built in the early 1960s. [Paul] decided that instead of the usual recapping, he’d go all the way and replace every component with fresh ones. That proved easier said than done; things have changed a lot in five decades, and resistors are a lot smaller than they used to be. Finding hookup wire to match the original was also challenging, as was disemboweling some of the electrolytic cans so they could be recapped. The finished product is beautiful, though — even the Magic Eye tube works — and [Paul] reports that the noise level is so low he wasn’t sure if turned it on at first.

We’ve covered the rise and fall of Heathkit, as well as their many attempted comebacks, including an inexplicable solder-free radio and the “world’s most reliable” clock. Looking at these offerings, we think [Paul] may be onto something here.

’75 Nixie Multimeter As Digital Dice

January 20, 2020 by 10 Comments

For the casual Monopoly or Risk player, using plain six-sided dice is probably fine. For other games you may need dice with much more than six sides, and if you really want to go overboard you can do what [John] did and build electronic dice with a random number generator if you really need to remove the pesky practice of rolling physical dice during your games of chance.

The “digital dice” he built are based on a multimeter from 1975 which has some hardware in it that was worth preserving, including a high quality set of nixie tubes. Nixies can be a little hard to come by these days, but are interesting pieces of hardware in their own right. [John] added some modern hardware to it as well, including an AVR microcontroller that handles the (pseudo) random number generation. A hardware switch tells the microcontroller how many sides the “die” to be emulated will need, and then a button generates the result of the roll.

This is a pretty great use for an old piece of hardware which would otherwise be obsolete by now. [John] considers this a “Resto-Mod” and the finish and quality of the build almost makes it look all original. It’s certainly a conversation piece at the D&D sessions he frequents.

Heathkit’s New RF Meter: Who Is It For?

June 23, 2017 by 25 Comments

Electronic hackers and ham radio operators of a certain age have a soft spot for the Heathkit brand. Maybe that’s why we had a rush of nostalgia when we saw the Heathkit site had a new product. You may recall that Heathkit had gone the way of the dodo until a few years ago when the brand started to resurface. Their latest kit is a precision RF meter which is available on preorder.

Before there were websites and hacker spaces and all the modern push to “do it yourself,” Heathkit was teaching people electronics through kit building. Sure, they were known for ham radio and test equipment, but many people built stereos (hi-fi), TVs, radio control gear, computers, and even robots. All with manuals that are hard to imagine if you haven’t seen one. They were world-class.

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Measuring Capacitors At The Birth Of Rock And Roll

April 15, 2017 by 3 Comments

The late 1950s [Bill Haley], [Elvis Presley], and [Little Richard] were building a new kind of music. Meanwhile, electronic hobbyists were building their own gear from Heathkit. A lot of that gear shows you how far we’ve come in less than a century. [Jeff Tranter’s] YouTube channel is a great way to look at a lot of old Heathkit gear, including this really interesting “direct reading capacity meter.” You can see the video, below.

Measuring capacitance these days is easy. Many digital multimeters have that function. However, those didn’t exist in the 1950s–at least, not in the way we know them. The CM-1 weighed 5 pounds, had several tubes, and cost what would equate to $250 in today’s prices. Unlike other instruments of the day, though, the capacitance was read directly off a large analog meter (hence, the name). You didn’t have to interpret readings using a nomograph or move a knob to balance a bridge and read the knob’s position.

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