Rewritable ROM For The Mac Plus

December 23, 2014 by Brian Benchoff 10 Comments

The Macintosh Classic – a small all-in-one computer with a 9″ monochrome screen – was one of the more interesting machines ever released by Apple. It was the company’s first venture into a cost-reduced computer, and the first Macintosh to sell for less than $1000. Released in 1990, its list of features were nearly identical to the Macintosh Plus, released four years earlier. The Classic also had an interesting feature not found in any other Mac. It could boot a full OS, in this case System 6.0.3, by holding down a series of keys during boot. This made it an exceptional diskless workstation. It was cheap, and all you really needed was a word processor or spreadsheet program on a 1.44 MB floppy to do real work.

[Steve] over at Big Mess O’ Wires had the same idea as the Apple engineers back in the late 80s. Take a Macintosh Plus, give it a bit more ROM, and put an OS in there. [Steve] is going a bit farther than those Apple engineers could have dreamed. He’s built a rewritable ROM disk for the Mac Plus, turning this ancient computer into a completely configurable diskless workstation.

The build replaces the two stock ROM chips with an adapter board filled with 29F040B Flash chips. They’re exactly what you would expect – huge, old PDIPs loaded up with Flash instead of the slightly more difficult to reprogram EEPROM. Because of the additional space, two additional wires needed to connected to the CPU. The result is a full Megabyte of Flash available to the Macintosh at boot, in a computer where the normal removable disk drive capacity was only 800kB.

The hardware adapter for stuffing these flash chips inside a Mac Plus was made by [Rob Braun], while the software part of this build came from [Rob] and [Doug Brown]. They studied how the Macintosh Classic’s ROM disk driver worked, and [Rob Braun] developed a stand-alone ROM disk driver with a new pirate-themed startup icon. [Steve] then dug in and created an old-school Mac app in Metrowerks Codewarrior to write new values to the ROM. Anything from Shufflepuck to Glider, to a copy of System 7.1 can be placed on this ROM disk.

This isn’t the first time we’ve seen ROM boot disks for old Macs. There was a lot of spare address space floating around in the old Mac II-series computers, and [Doug Brown] found a good use for it. Some of these old computers had optional ROM SIMM. You can put up to 8 Megabytes in the address space reserved for the ROM, and using a similar ROM disk driver, [Doug] can put an entire system in ROM, or make the startup chime exceptionally long.

The Heathkit Mystery

December 22, 2014 by Brian Benchoff 58 Comments

Heathkit is a company that requires no introduction. From the mid-40s until the 90s, Heathkit was the brand for electronic kits ranging from test equipment, HiFis, amateur radio equipment, computers, to freakin’ robots. Their departure was a tragic loss for generations of engineers, electronic tinkerers and hobbyists who grew up with these excellent and useful kits.

Although Heathkit is dead, 2013 brought an announcement that Heathkit was back in the biz. A Facebook page was launched, a Reddit AMA was held, and the news was that Heathkit would rise from the dead in the first half of 2014. It’s now Christmas, 2014, and there’s no sign of Heathkit anywhere. Adafruit has been keeping a watchful eye on the on the (lack of) developments, and the only surprising thing to report is that there is nothing to report. There has been no new announcement, there are no new products, the “official” Heathkit website hasn’t been updated in a year, and no one knows what’s going on.

Adafruit has decided to dig into the matter, and while they’ve come up with a few items of note, there’s not much to report. A trademark for ‘HEATHKIT’ was filed October 27, 2014 – two months ago. An email was sent to the attorney of record and there has been no response.

This trademark was granted to Heathkit Company, Inc., incorporated in Delaware. Searching for any companies in Delaware using the Heathkit name returns exactly two results: Heathkit Company, Inc., and Heathkit Holdings, Inc.. Adafruit is probably going to pay the $20 to the Delaware Department of State to get the detailed information that includes Heathkit’s tax assessment and tax filing history.

The last bit of information comes from a whois on the heathkit.com domain. The relevant contacts have been emailed, and there are no further details. The Heathkit virtual museum was contacted for information, as was the news editor for ARRL.org. Nobody knows anything, or at least nobody is telling anybody anything.

To date, the only physical evidence of Heathkit’s rebirth is a geocache that was left at Brooklyn Bridge Park, announced during the Reddit AMA. This geocache was recovered by reddit user IFoundTheHeathKit, a throwaway account that had no posts before or since finding the cache. We have no idea what was in that geocache, what the ‘secret passphrase’ or set of instructions was, or if anything ever came of the promise to send one of the first new kits.

So there ‘ya go. A lot of words but no information. If you have any info, the Adafruit crew would like to have a word with you.

Update

The person who found the Heathkit geocache has been found:

The full comment referred to below is,

Hey, person who found the Heathkit geocache here. The secret passcode was an Einstein quote about radio vs wired communication (invisible cats), and they said they’d send me something in early 2014. Never had any communication except through FB, and they haven’t replied to any of my recent messages.

IFoundTheHeathKit might want to email Adafruit with a copy of all the emails.

[Fran] & [Bil]’s Dinosaur Den

July 2, 2014 by Brian Benchoff 7 Comments

I suppose I can take credit for introducing the super awesome [Fran Blanche] to Hackaday’s very own crotchety old man and Commodore refugee [Bil Herd]. I therefore take complete responsibility for [Fran] and [Bil]’s Dinosaur Den, the new YouTube series they’re working on.

The highlight of this week’s episode is a very vintage Rubicon mirror galvanometer. This was one of the first ways to accurately measure voltage, and works kind of like a normal panel meter on steroids. In your bone stock panel meter, a small coil moves a needle to display whatever you’re measuring. In a mirror galvanometer, a coil twists a wire that is connected to a mirror. By shining a light on this mirror and having the reflected beam bounce around several other mirrors, the angle of the mirror controlled by the coil is greatly exaggerated, making for a very, very accurate measurement. It’s so sensitive the output of a lemon battery is off the scale, all from a time earlier than the two dinosaurs showing this tech off. Neat stuff.

One last thing. Because [Bil] and [Fran] are far too proud to sink to the level of so many YouTube channels, here’s the requisite, “like comment and subscribe” pitch you won’t hear them say. Oh, [Bil] knows the audio is screwed up in places. Be sure to comment on that.

Continue reading “[Fran] & [Bil]’s Dinosaur Den” →

[Fran]’s LEDs, Nixies, And VFDs.

January 4, 2014 by Brian Benchoff 21 Comments

With a love of blinky and glowey things, [Fran] has collected a lot of electronic display devices over the years. Now she’s doing a few teardowns and tutorials on some of her (and our) favorite parts: LEDs and VFD and Nixie tubes

Perhaps it’s unsurprising that someone with hardware from a Saturn V flight computer also has a whole lot of vintage components, but we’re just surprised at how complete [Fran]’s collection is. She has one of the very first commercial LEDs ever made. It’s a very tiny red LED made by Monsanto (yes, that company) packaged in a very odd lead-and-cup package.

Also in her LED collection is a strange Western Electric part that’s green, but not the green you expect from an LED. This LED is more of an emerald color – not this color, but more like the green you get with a CMYK process. It would be really cool to see one of these put in a package with red, green, and blue LED, and could have some interesting applications considering the color space of an RGB LED.

Apart from her LEDs, [Fran] also has a huge collection of VFD and Nixie tubes. Despite the beliefs of eBay sellers, these two technologies are not the same: VFDs are true vacuum tubes with a phosphorescent coating and work something like a CRT turned inside out. Nixies, on the other hand, are filled with a gas (usually neon) that turns to plasma when current flows through one of the digits. [Fran] has a ton of VFDs and Nixies – mostly military surplus – and sent a few over to [Dave Jones] for him to fool around with.

It’s all very cool stuff and a great lead-in to what we hear [Fran] will be looking at next: electroluminescent displays found in the Apollo Guidance Computer.

Videos below.

Continue reading “[Fran]’s LEDs, Nixies, And VFDs.” →

Build An Audio Spectrum Analyzer The Analog Way

January 3, 2014 by Adam Fabio 18 Comments

bandpass

[Ryan] wanted a spectrum analyzer for his audio equipment. Rather than grab a micro, he did it the analog way. [Ryan] designed a 10 band audio spectrum analyzer. This means that he needs 10 band-pass filters. As the name implies, a band-pass filter will only allow signals with frequency of a selected band to pass. Signals with frequency above or below the filter’s passband will be attenuated. The band-pass itself is constructed from a high pass and a low pass filter. [Ryan] used simple resistor capacitor (RC) filters to implement his design.

All those discrete components would quickly attenuate [Ryan’s] input signal, so each stage uses two op-amps. The first stage is a buffer for each band. The second op-amp, located after the band-pass filters, is configured as a non-inverting amplifier. These amplifiers boost the individual band signals before they leave the board. [Ryan] even added an “energy filler” mode. In normal mode, the analyzer’s output will exactly follow the input signal. In “energy filler” (AKA peak detect) mode, the output will display the signal peaks, with a slow decay down to the input signal. The energy filler mode is created by using an n-channel FET to store charge in an electrolytic capacitor.

Have we mentioned that for 10 bands, all this circuitry had to be built 10 times? Not to mention input buffering circuitry. With all this done, [Ryan] still has to build the output portion of the analyzer: 160 blue LEDs and their associated drive circuitry. Going “all analog” may seem crazy in this day and age of high-speed micro controllers and FFTs, but the simple fact is that these circuits work, and work well. The only thing to fear is perf board solder shorts. We think debugging those is half the fun.

Inside The Clapper

September 29, 2013 by Brian Benchoff 21 Comments

clapper

Hackaday readers above a certain age will probably remember the fabulously faddish products developed by Joseph Enterprises. These odd gadgets included the Ove’ Glove, VCR Co-Pilot, the Creosote Sweeping Log, and Chia Pet (Cha-Cha-Cha-Chia) as mainstays of late night commercials, but none were as popular as The Clapper, everyone’s favorite sound-activated switch from the 1980s. [Richard] put up a great virtual teardown of The Clapper, that provides a lot of insight into how this magic relay box actually works, along with some historical context for the world The Clapper was introduced to.

Sound activated switches are nothing new, but the way The Clapper did it was just slightly brilliant. Instead of listening to every sound, the mic inside the magic box sends everything through a series of filters to come up with a very narrow bandpass filter centered around 2500 Hz. This trigger is analyzed by a SGS Thompson ST6210 microcontroller ( 4MHz, ~1kB ROM, 64 bytes of RAM, and 12 I/O pins ) to listen for two repeating triggers within 200 milliseconds. The entire system – including the source code for the MCU – can be seen in the official patent, US5493618.

The Clapper sold many millions of units at a time when a lot of homes were assuredly in a pre-microelectronics world. Yes, in 1986, a lot of TVs had microcontrollers and maybe a washer/dryer combo may have had a few thousand transistors between them. Other than that, The Clapper was many household’s introduction to the ubiquitous computing power we see today, and all with less capability than an Arduino.

Hackaday Retro Roundup: Ultraportables Edition

January 12, 2013 by Brian Benchoff 17 Comments

front

A few months ago, we rolled out an updated Hackaday, a badly needed new layout replacing the HTML and CSS that had remained unchanged since 2004. Of course a few people didn’t like change and complained about slow load times. We’ve experienced a slightly slower load time as well, so we’ll just wait until the year 2020 when our computers are many times faster and our Internet is provided by Google Fiber. Until then, our pokey battlestations and vintage computers can still check out a few classic hacks on our retro site. Here’s a few retro successes – Hackaday readers who pulled out their old tech and loaded up the retro site – that have come in over the past weeks and months.

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