Ancient Teletype Revived in Labor of Retrocomputing Love

Readers with not too many years under their belts may recall a time when the classic background sound effect for radio and television news programs included a staccato mechanical beat, presumably made by the bank of teletype machines somewhere in the studio, clattering out breaking stories onto rolls of yellow paper. It was certainly true that teletypes were an important part of the many communications networks that were strung together over the 20th century, but these noisy, greasy beasts had their day and are now largely museum pieces.

Which is exactly where the ancient Model 19 Teletype machine that [CuriousMarc] and company are restoring is destined. Their ongoing video series, six parts long as of this writing, documents in painstaking detail how this unit worked and how they are bringing it back to its 1930s glory. Teletypes were made to work over telephone lines with very limited bandwidth, and the hacks that went into transmitting text messages with a simple 5-bit encoding scheme are fascinating. The series covers the physical restoration of the machine, obviously well-loved during its long service with the US Navy. Of particular interest is the massive power supply with its Thyratron tubes and their mysterious blue glow.

The whole series is worth a watch if you’re even slightly interested in retrocomputing. We’re particularly taken with the mechanical aspects of these machines, though, which have a lot in common with mechanical calculators. [Al Williams] recently covered the non-replacement of the power supply caps for this unit, which is an interesting detour to this restoration.

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Amiga Repairs Put One Tough Little Machine Back in Service

Returning a piece of retro hardware to factory condition is generally a labor of love for the restorationist. A repair, on the other hand, is more about getting a piece of equipment back into service. But the line between repair and restoration is sometimes a fine one, with the goals of one bleeding over into the other, like in this effort to save an otherwise like-new Amiga 2000 with a leaky backup battery.

Having previously effected emergency repairs to staunch the flow of electrolyte from the old batteries and prevent further damage, [Retromat] entered the restoration phase of the project. The creeping ooze claimed several caps and the CPU socket as it spread across the PCB, but the main damage was to the solder resist film itself. In the video below you can clearly see flaky, bubbly areas in the mask where the schmoo did its damage.

Using a fiberglass eraser, some isopropyl alcohol, and far more patience than we have, [Retromat] was able to remove the damaged resist to reveal the true extent of the damage below. Thankfully, most of the traces were still intact; only a pair of lines under the CPU socket peeled off as he was removing it. After replacing them with fine pieces of wire, replacing the corroded caps and socket, and adding a coin-cell battery holder to replace the old battery, the exposed traces were coated with a varnish to protect them and the machine was almost as good as new.

Amigas were great machines in their day and launched more than one business. They’ve proved their staying power too, some even in mission-critical roles.

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Replace Old Electrolytics? Not So Fast… Maybe

[CuriousMarc] was restoring an old Model 19 TeleType. The design for these dates back to the 1930s, and they are built like tanks (well, except for the ones built during the war with parts using cheaper metals like zinc). Along the way, he restored a hefty tube-based power supply that had two very large electrolytic capacitors. These dated from the 1950s, and common wisdom says you should always replace old electrolytics because they don’t age well and could damage the assembly if powered up. [Marc] didn’t agree with common wisdom, and he made a video to defend his assertion which you can see below.

If you look at the construction of electrolytic capacitors, one plate of the capacitor is actually a thin layer that is formed electrically. In some cases, a capacitor with this plate is damaged can be reformed either by deliberate application of a constant current or possibly even just in normal operation.

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The Hacky Throttle Repair That Got Me On The Road Again

Old cars are great. For the nostalgia-obsessed like myself, getting into an old car is like sitting in a living, breathing representation of another time. They also happen to come with their fair share of problems. As the owner of two cars which are nearing their 30th birthdays, you start to face issues that you’d never encounter on a younger automobile. The worst offender of all is plastics. Whether in the interior or in the engine bay, after many years of exposure to the elements, parts become brittle and will crack, snap and shatter at the slightest provocation.

You also get stuck bolts. This was the initial cause of frustration with my Volvo 740 Turbo on a cold Sunday afternoon in May. As I tried in vain to free the fuel rail from its fittings, I tossed a spanner in frustration and I gave up any hope of completing, or indeed, starting the job that day. As I went to move the car back into the driveway, I quickly noticed a new problem. The accelerator was doing approximately nothing. Popping the hood, found the problem and shook my head in resignation. A Volvo 740 Turbo is fitted with a ball-jointed linkage which connects the accelerator cable to the throttle body itself. In my angst, the flying spanner had hit the throttle body and snapped the linkage’s plastic clips. It was at this point that I stormed off, cursing the car that has given me so much trouble over the past year.

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Ask Hackaday: How Do You DIY a Top-Octave Generator?

One of the great joys of Hackaday are the truly oddball requests that we sometimes get over the tip line. Case in point: [DC Darsen] wrote in with a busted 1970s organ in need of a new top-octave generator, and wondered if we could help. He had found a complicated but promising circuit online, and was wondering if there was anything simpler. I replied “I should be able to get that done with a single Arduino” and proceeded to prove myself entirely wrong in short order.

So we’re passing the buck on to you, dear Hackaday reader. Can you help [DC Darsen] repair his organ with a minimum amount of expenditure and hassle? All we need to do is produce twelve, or maybe thirteen, differently pitched square waves simultaneously.

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Motor test bench talks the torque

Salvaging a beefy motor is one life’s greatest pleasures for a hacker, but, when it comes to using it in a new project, the lack of specs and documentation can be frustrating. [The Post Apocalyptic Inventor] has a seemingly endless stockpile of scavenged motors, and decided to do something about the problem.

Once again applying his talent for junk revival, [TPAI] has spent the last year collecting, reverse-engineering and repairing equipment built in the 1970s, to produce a complete electric motor test setup. Parameters such as stall torque, speed under no load, peak power, and more can all easily be found by use of the restored test equipment. Key operating graphs that would normally only be available in a datasheet can also be produced.

The test setup comprises of a number of magnetic particle brakes, combined power supply and control units, a trio of colossal three-phase dummy loads, and a gorgeously vintage power-factor meter.

Motors are coupled via a piece of rubber to a magnetic particle brake. The rubber contains six magnets spaced around its edge, which, combined with a hall sensor,  are used to calculate the motor’s rotational speed. When power is applied to the coil inside the brake, the now magnetised internal powder causes friction between the rotor and the stator, proportional to the current through the coil. In addition to this, the brake can also measure the torque that’s being applied to the motor shaft, which allows the control units to regulate the brake either by speed or torque. An Arduino slurps data from these control units, allowing characteristics to be easily graphed.

If you’re looking for more dynamometer action, last year we featured this neatly designed unit – made by some Cornell students with an impressive level of documentation.

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Terrible RC Transmitter Made Less Terrible

It should probably go without saying that we’ve got nothing against the occasional bout of elaborate troubleshooting and repair, in fact it’s one of the most common things we cover here. As it turns out, people aren’t overly fond of being fleeced, and there are a lot of smart people out there who will put a lot of work in to keep from having to toss a favorite piece of gear into the trash. We can’t fault them for that.

But we have to say, we generally don’t see those kind of elaborate repairs for something brand new. Unfortunately, that’s exactly what [Marek Baczynski] had to do when trying to review the new iRangeX transmitter for his YouTube channel “dronelab”. He found a transmitter that was so poorly designed and constructed that he had to address a laundry list of issues to make the thing halfway tolerable. As you might expect, he’s not suggesting anyone go run and pick this one up.

The biggest problem is a fundamental flaw with how the gimbals are constructed. Due to poorly mated surfaces between the potentiometer and the stick itself, the accuracy of the controller is very low. The potentiometers don’t even return to zero when the sticks are released. Some tape was used to tighten up the connection and make the controller usable, but such poor tolerances are hard to forgive when accurate control is essentially the whole point of the device.

The other issues took a bit more debugging to figure out. The TX made an absolutely terrible screeching sound when turned on, but [Marek] was sure he was hearing a little bit of melody under the din. Putting the signal through the oscilloscope, he was able to confirm his suspicions. As it turns out, the buzzer used in the TX has a built in tone generator that was overriding the intended melody. Switching it out for a basic buzzer fixed the issue. Similarly, an issue where the radio wouldn’t turn on if it was recently turned off was tracked back to a resistor of the wrong value. Putting a higher lower value resistor in its place sorted that out as well.

It’s hard to imagine how this device made it out of the factory with so many wrong or unsuitable components, but here we are. Not that this would be acceptable at any price point, but as [Marek] points out in the video, it isn’t as if this radio is even all that cheap. For nearly $90 USD, it doesn’t seem unreasonable to expect something that actually works.

This isn’t the first time he’s put “cheap” RC hardware through the wringer. We recently covered his efforts to quantify latency in different transmitters. As the RC transmitter world gets increasingly competitive, detailed analysis like these help separate the real gear from the toys.

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