Fixing An IBM 1401 Computer To Get It Printing Again


via Hackaday

The IBM 1401 is a classic computer which IBM marketed throughout the 1960s, late enough for it to have used transistors rather than vacuum tubes, which is probably a good thing for this story. For small businesses, it was often used as their main data processing machine along with the 1403 printer. For larger businesses with mainframes, the 1401 was used to handle the slower peripherals such as that 1403 printer as well as card readers.

Broken germanium transistor
Broken germanium transistor

The Computer History Museum in Mountain View, CA has two working 1401s as well as at least one 1403 printer, and recently whenever the printer printed out a line, the computer would report a “print check” error. [Ken Shirriff] was among those who found and fixed the problem and he wrote up a detailed blog entry which takes us from the first test done to narrow down the problem, through IBM’s original logic diagrams, until finally yanking out the suspect board and finding the culprit, a germanium transistor which likely failed due to corrosion and an emitter wire that doesn’t look solidly connected. How do they know that? In the typical [Ken]-and-company style which we love, they opened up the transistor and looked at it under a microscope. We get the feeling that if they could have dug even deeper then they would have.

If you’re unfamiliar with the work of this team who maintain the machines at the museum, you’ll want to read up on how they recently got a 1401 to run FORTRAN II code.

C64 Keyboard Helps Keep The Memory Alive


via Hackaday

To say that the Commodore 64 was an important milestone in the history of personal computing is probably a bit of an understatement. For a decent chunk of the 1980s, it was the home computer, with some estimates putting the total number of them sold as high as 17 million. For hackers of a certain age, there’s a fairly good chance that the C64 holds a special spot in their childhood; perhaps even setting them on a trajectory they followed for the rest of their lives.

At the risk of showing his age, [Clicky Steve] writes in to tell us about the important role the C64 played in his childhood. He received it as a gift on his fifth birthday from his parents, and fondly remembers the hours he and his grandfather spent with a mail order book learning how to program it. He credits these memories with getting him interested in technology and electronic music. In an effort to keep himself connected to those early memories, he decided to build a modern keyboard with C64 keycaps.

As you might expect, the process started with [Steve] harvesting the caps from a real Commodore, in fact, the very same computer he received as a child. While the purists might shed a tear that the original machine was sacrificed to build this new keyboard, he does note that his C64 had seen better days.

Of course, you can’t just pull the caps off of C64 and stick them on a modern keyboard. [Steve] found the STLs for a 3D printable C64 to Cherry MX adapter on GitHub, and had 80 of them professionally printed as he doesn’t have access to an SLS printer. He reports the design works well, but that non-destructively removing the adapters from the caps once they are pressed into place probably isn’t going to happen; something to keep in mind for others who might be considering sacrificing their personal C64 for the project.

[Steve] installed the caps on a Preonic mechanical keyboard, which worked out fairly well, though he had to get creative with the layout as the C64 caps didn’t really lend themselves to the keyboard’s ortholinear layout. He does mention that switches a bit heavier than the Cherry MX Whites he selected would probably be ideal, but overall he’s extremely happy with his functional tribute to his grandfather.

If you’re more of a purist, you can always adapt the C64 keyboard directly to USB. Or go in the complete opposite direction and put a Raspberry Pi into a C64 carcass.

Golf Practice Made Easy with Robotics

via Hackaday:

When you think of sports, you usually think of something that takes a lot of physical effort. Golf is a bit different. Sure, you can get some walking in if you don’t take a cart. But mostly golfing is about coordination and skill and less about physical exertion. Until you want to practice driving. You hit a bucket of balls and then you have to go walk around and pick them up. Unless you have help, of course. In particular, you can delegate the task to a robot.

The robot that [webzuweb] built looks a little like a plywood robot vacuum. However, instead of suction, it uses some plywood disks to lift the balls and deposit them in a hopper. The electronics consist of an Arduino and an Orange Pi Lite. A GPS tells the robot where it is and it develops a search pattern based on its location.

Although [webzuweb] notes he isn’t done with the project, it looks pretty good. He describes the software, but it doesn’t appear to be posted anywhere. However, he does describe its operation and how it changes mode based on its current state.

We can’t decide if golf is really a sport or more of a game. We were surprised to read that if you carry your own bag and don’t use a cart you can burn about 360 calories an hour which is somehow more than a gymnast burns, which hardly seems possible.

Of course, most people use a cart and a caddy, so they aren’t going to burn those calories. If you are in the market for a cool cart, we liked this one. Or, perhaps you’d like one with more power.

What’s a Couplate? The Stepping Stone to Integrated Circuits


via Hackaday:

We are spoiled these days because you can shop online and get all manner of inexpensive electronic goodies shipped to your door. This is due to the fantastic electronic fabrication workflow that has grown into a global powerhouse, facilitated by complex yet inexpensive integrated circuits! But it took a few intermediate steps to get here, and one of those is known as a couplate.

When I was a kid, the big deal was to find an old radio in the trash. You could spend a few hours stripping all sorts of parts from the thing and add it to your collection for a future project. Of course, old radios from the 1970s and earlier had a lot of the usual parts we use today, even though many of them were bigger — no surface mount parts yet. Since older radios were the usual find in a dumpster, tubes were common but you could find some transistor radios.

Once in a while something older. There would be a little box with some wires poking hiding in an old radio from the 1940s or 1950s (too early for ICs). In a way, though, these were predecessors to the Integrated Circuit and they went by a few names, depending on who sold them. PEC (Printed Electronic Circuit), a couplate, or a BulPlate, are all names for hardware that was a stepping stone between discrete circuitry and ICs.

Collections of Passive Components

PECs were most common in tube sets and they didn’t have any active circuitry. They sere often set up to handle audio filtering or some other common task using just resistors and capacitors. Companies known for these devices Areovox (PEC), Centralab (couplate), or Sprague (BulPlates). The example shown here, the PC-33 from Centralab, sold for fifty cents and had three terminals

The PC-33 is not terribly impressive, but a PC-151 (see right) had 7 pins and the schematic is quite impressive. The couplate itself only had the bold components, not the tubes and other components showed in gray. That little jewel cost about $1.15. Doesn’t sound like much, but in 1950 terms that was like $12 today. In fact, we found one on eBay for $11.90 so maybe there’s something to that.

Another place you would find these were in TVs where a vertical integrator PEC could help with sweeping the CRT. It was basically three resistors and three capacitors set up to help generate a vertical deflection ramp.

Active Devices

There were a very few PECs made with tubes as active devices. Well, more accurately, with tube sockets. Some 1950 promotional material from Centralab said:

There’s never been an electronic device like Centralab’s Ampec. It is one compact unit permanently bonded to a master plate with all components of an audio amplifier — tube sockets, capacitors, resistors, wiring. It’s a full three tube three stage speech amplifier.

Centralab Ampecs are widely used in hearing aids, for the most trouble-free performance ever attained. Ampec has other interesting applications, as mike pre-amplifier, etc.

The module — without tubes — was an inch and a quarter wide and nearly as long. An Allied Radio catalog described it as “no larger than a book of paper matches” and sold it for $15.29, including the tubes.


The American Radio History site has so many old magazines and catalogs and, as usual, it didn’t let us down when looking for more information about these old components. The December 1949 issue of Radio and Television News (PDF) has the start of a two-part article entitled “Printed Circuits.” The cover with the smiling housewife, beaming at her brand new intercom while her five inch TV set perches next to the sink is priceless, too.

According to the article, Centralab began mass producing printed circuit boards in 1945 for a mortar shell proximity fuse. But these were not printed circuits in the sense that we think of them today. A ceramic substrate was the base for silver and graphite paint applied via silk screen. The silver makes wires and the graphite makes resistors. Seems like conductive ink circuits isn’t at all new concept!

The ceramic was fired in an oven and capacitors were attached. In some cases, conductive paint on both sides of the ceramic would form capacitors, too. Of course, small flat inductors were also possible. Supposedly, inductors could be covered with an insulator and painted with ferrite paint to increase inductance, but that doesn’t sound like it would get you very far. In more modern times, this same basic technique is how you make hybrid thick film circuits, not uncommon in high-reliability applications.

The author notes that you can use other methods such as rubber stamping or lithography to ink the printed circuit board. There was even talk of using decalcomania which is exactly what it sounds like, but I still had to look it up. There were many other methods that didn’t catch on over the long term. For example, “dusting” had metallic dust spread on a substrate and sintered in place much like some metal 3D printing processes. We were especially amused by the cylindrical boards that built circuits around a glass tube.

Build Up and Teardown

The second part of the article (PDF) covers creating your own printed circuits using conductive and resistive paint from DuPont. Since DuPont wasn’t going to sell you a few ounces of these paints, an enterprising Michigan company was selling smaller quantities and kits. You had to find your own substrate and we find it amusing that they suggested using an asbestos board.

A Russian site has a great teardown of an old tape machine that used modules like these. The tape player may look bulky by today’s standards with its large battery and tubes. However, for its day it was quite svelte and cheaper to manufacture thanks to the couplate technology.

It is hard to remember a time when consumer electronics were wired by hand with real wires. We’ve all seen computer backplanes that looked like plates of spaghetti. Printed circuit boards would change the face of electronics forever. Integrated circuit modules, even more. A look at the very early birth of these technologies is sobering when you realize all this was less than 100 years ago.

These methods didn’t last long. By 1969, boards were a bit more like we think of them, although there was still a ways to go. You might enjoy the Tektronix video talking about those kinds of boards, below. And it’s also worth a mention that one of most mesmerizing component assembly periods is tinkertoy and cordwood construction.


SMART Response XE Gets Wireless Bootloader

via Hackaday:

A few months back we first brought word of the progress being made in unlocking the SMART Response XE, an ATmega128RFA powered handheld computer that allowed teachers to create an interactive curriculum in the days before all the kids got Chromebooks. Featuring 2.4 Ghz wireless communication, a 384×160 LCD, and a full QWERTY keyboard, schools paid around $100 each for them 2010. Now selling for as little as $5 on eBay, these Arduino-compatible devices only need a little coaxing and an external programmer to get your own code running.

The previous post inspired [Larry Bank] to try his hand at hacking the SMART Response XE, and so far he’s made some very impressive progress. Not only has he come up with his own support library, but he’s also created a way to upload Arduino code to the devices through their integrated 802.15.4 radio. With his setup, you no longer need to open the SMART Response XE and attach a programmer, making it much easier to test and deploy software.

[Larry] has written up a very detailed account of his development process, and goes through the trouble of including his ideas that didn’t work. Getting reliable communication between two of these classroom gadgets proved a bit tricky, and it took a bit of circling around until he hit on a protocol that worked.

The trick is that you need to use one SMART Response XE attached to your computer as a “hub” to upload code to other XEs. But given how cheap they are this isn’t that big of a deal, especially considering the boost in productivity it will net you. [Larry] added a 5 x 2 female header to his “hub” XE so he could close the device back up, and also added a physical power switch. In the video after the break, you can see a demonstration of the setup sending a simple program to a nearby XE.

Between this wireless bootloader and the Arduboy compatibility covered previously, we’d suggest you get your SMART Response XE now. We wouldn’t be surprised if the prices of these things start going up like they did with the IM-ME.

The Quest For High Powered Blinky And Buzzing

Sometimes, we need devices to notify us of something. The oven timer is going off. Your phone has a push notification. The smoke detector battery is getting low. All of these problems can be solved with a buzzer or an LED. It’s a simple and cheap problem to solve.

But what if you need to know if something’s wrong with a diesel engine that throwing out 90 dB of noise? What if you’re not guaranteed to be around that engine? What if you need to tell everyone within a half mile that something is wrong. Again, LEDs and beepers, but the standard, off-the-shelf implementation isn’t going to cut it. You need massive amounts of buzzers and LEDs, and you’re going to need to drive them all with some reasonably high current. How do you solve that problem?

This is the problem [Tegwyn] had to solve for another one of his Hackaday Prize entries. The solution is what you would expect — buzzers and LEDs — but he’s putting some serious current behind these devices. There are, in fact, thermal considerations taken into account when you’re beeping this many buzzers.

The LEDs for this project are a handful of blindingly bright 1209 and 1206 SMD parts, and the buzzer is an obnoxiously loud SMD 97 dB buzzer. There are eight buzzers on this board. So, how do you drive these power-hungry devices? [Tegwyn] is using an L293E half-bridge motor driver, in a ‘Power-DIP’ package for relatively effective heat dissipation. Does it work? Oh, yes, and it’s very annoying. Take a look at the video below and judge for yourself. You can, indeed, make something louder and more annoying by adding more power.

via Hackaday

Arduino Powered Portable Function Generator

It’s probably not much of a stretch to say that many of us have taken on a project or two that were little more than thinly veiled excuses to add a new tool or piece of gear to our arsenal. There’s something to be said for a bench full of button-festooned test equipment blinking away, it’s like bling for nerds. But just like getting your name written out in diamonds, it can get expensive quick.

Luckily, the hacker has enough technology at their disposal these days that DIY test equipment can help fill your bench without emptying your wallet. [Faransky] has created a very impressive Arduino function generator that doesn’t skimp on the features. Capable of generating sine, triangle, and square waves up to 10MHz with its all-digital circuitry, it’s a piece of gear that’s well worth the $30 USD or so it should cost to build your own version.

For those worrying that [Faransky] is relying on the PWM functionality of the Arduino Nano to generate waveforms, have no fear. At the heart of the device is a AD9833 waveform generator; with the Arduino, rotary encoder, and 16×2 LCD providing an interface to control it over SPI.

Unfortunately, the AD9833 doesn’t have a way to control amplitude, something which is pretty important in a function generator. So [Faransky] uses a X9C104P 100KOhm 8-bit digital potentiometer as a voltage divider on the chip’s output.

To wrap up the build, he added a 2000mAh 3.7V Li-Ion battery and TP4056 charger, with a DC-DC boost converter to get 5V for the Arduino. Though if you wanted to create a benchtop version of this device, you could delete those components in favor of a 5V AC/DC adapter.

We’ve seen our fair share of DIY function generators, ranging from minimalist builds to hardware that could pass for a commercial offering. We’ve even seen some cheap turn-key function generators, though the usual warnings about getting what you pay for apply.

via Hackaday