Building A Tube-Based Stereo Amp, In Classic Style

It’s not every day we see the results of someone putting their own spin on a vintage tube amp, but that’s exactly what [lens42] did in creating the McIntosh 217, created as a “mini” version of the McIntosh MC275, a classic piece of audio equipment. Both are pictured next to each other, above.

When it comes to vintage hi-fi stereo amplifiers, two units had particular meaning for [lens42]: the McIntosh MC275 Power Amp, and the Dynaco ST35. The Dynaco was a more budget-friendly amplifier, but looked like a plain box. The McIntosh, however, proudly showed off its tubes and transformers in all their glory. The “McIntosh 217” is design-wise basically a smaller McIntosh MC275, with the innards of a Dynaco ST35.

With so much needing to be designed from the ground up, CAD was invaluable. Component layout, enclosure design, and even wiring and labeling all had to be nailed down as much as possible before so much as heating up the soldering iron. Even so, there were a few hiccups; a vendor had incorrect measurements for a tube socket which meant that the part would not fit. A workaround involved modifying the holes and as luck would have it, the change wasn’t an eyesore. Still, [lens42] reminds us all that whenever you can, have the required parts in-hand for confirmation of dimensions before sending CAD files off for cutting or fabrication.

Many of us can relate to the fact that the whole project was a labor of love and made no real financial sense, but the end result is fantastic, and creating such a thing is something all of us — not just chasers of that elusive “tube sound” — can appreciate.

Fix Old Caps, But Keep That “Can Capacitor” Look

Vintage electronics and capacitor replacements tend to go hand-in-hand. Why? Because electrolytic capacitors just don’t last, not the way most other components do, anyway.

The metal terminal ring and the central plate are kept for re-use, and the metal case re-crimped after the internals of the capacitor are replaced with a modern equivalent.

It’s one thing to swap old caps with modern replacements, but what about electronics where the components are not hidden away, and are an important part of the equipment’s look? [lens42] shares a method for replacing antique can-style capacitors in a way that leaves them looking completely original. All it takes is some careful application of technique.

The first thing to do is carefully file away the crimp of the metal can until one can release the ring and plate that hold the terminals. Once that is off, the internals can be pulled from the metal can for disposal. Since the insides of the old cap won’t be re-used, [lens42] recommends simply drilling a hole, screwing in a lag bolt to use as a handle, and pulling everything out. There’s now plenty of space inside the old can to hold modern replacements for the capacitor, and one can even re-use the original terminals.

That leaves the job of re-crimping the old can around the terminal ring to restore a factory-made appearance. To best do this, [lens42] created a tapered collar. Gently hammering the can forces the bottom into the taper, and the opening gradually crimps around the terminal ring. It’s also possible to carefully hammer the flange directly, but the finish won’t be as nice. This new crimp job may not look exactly the same as before, but once the cap is re-installed into the original equipment, it won’t be possible to tell it has been modified in any way.

If this sounds a bit intimidating, don’t worry. [lens42] provides plenty of pictures. And if this kind of thing is up your alley, you may want to check out the Caps Wiki, an effort to centralize and share details about tech repair, especially for vintage electronics.

A ’70s TV With ’20s Parts

Keeping older technology working becomes exponentially difficult with age. Most of us have experienced capacitor plague, disintegrating wire insulation, planned obsolescence, or even the original company failing and not offering parts or service anymore. To keep an antique running often requires plenty of spare parts, or in the case of [Aaron]’s vintage ’70s Sony television set, plenty of modern technology made to look like it belongs in a machine from half a century ago.

The original flyback transformer on this TV was the original cause for the failure of this machine, and getting a new one would require essentially destroying a working set, so this was a perfect candidate for a resto-mod without upsetting any purists. To start, [Aaron] ordered a LCD with controls (and a remote) that would nearly fit the existing bezel, and then set about integrating the modern controls with the old analog dials on the TV. This meant using plenty of rotary encoders and programming a microcontroller to do the translating.

There are plenty of other fine details in this build, including audio integration, adding modern video and audio inputs like HDMI, and adding LEDs to backlight the original (and now working) UHF and VHF channel indicators. In his ’70s-themed display wall, this TV set looks perfectly natural. If your own display wall spotlights an even older era, take a look at some restorations of old radios instead.

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The Tools That Lovingly Tore Apart A Vintage Computer Game

The structure of computer game assets can be a bit of a mystery, even more so the older a game is, and some amount of reverse-engineering can be expected when pulling apart a game like 1995’s Night Light.

[voussoir] had fond memories of this game by GTE Entertainment, which had an interesting “flashlight” mechanic to serve the exploration theme. Spooky shapes in dark rooms would be revealed to be quite ordinary (and therefore not scary at all) once illuminated with a flashlight, which was directed by the mouse.

Extracting game assets was partly straightforward, thanks to many of them being laid out in a handy folder structure, with .bmp files for each level in a modest resolution. But there were also some unusual .mov files that were less than a second long, and those took a little more work to figure out.

It turns out that these unusual movie files were 80 frames in length, and each frame was a tile of a larger image. [voussoir] used ffmpeg to extract each frame, then wrote a Python script to stitch the tiles together. Behold! The results are high-resolution versions of each level’s artwork. Stitching the first 16 frames into a 4×4 grid yields a 1024×768 image, and the remaining 64 frames can be put into a 8×8 grid for a fantastic 2048×1376 version. The last piece was extracting audio, but sadly the ISO [voussoir] was using seems to have had errors, and not all the audio survived.

With intact assets in hand, [voussoir] was able to re-create the core of the game, which can be seen about halfway down into the writeup. Audio clues play simply while the flashlight effect is re-created in the browser with the game’s original level artwork, and it’s enough to ring those nostalgia bells. It’s a pretty successful project, even though not all of the assets have been tracked down, and not all of the audio was able to be extracted due to corruption. If you have any insights on that front, don’t keep them to yourself! Send [voussoir] an email, or chime in here in the comments.

Reverse engineering has a strong history when it comes to games, and has manifested itself in sometimes unusual ways, like the time Atari cracked the NES. Had the subsequent legal challenge gone differently, the game landscape might have looked very different today.

IBM PCjr Types Again, Thanks To KeybJr

Most of us think of keyboards — even vintage ones — as being fairly standardized and interchangeable, but that isn’t the case for the IBM PCjr. Its keyboard was quite unlike most others of its time, which means that a PCjr without an original keyboard is pretty much a dust collector. That’s what led [Jozef Bogin] to create the KeybJr, a piece of hardware that allows one to use any AT, XT, or PS/2 keyboard with the IBM PCjr.

The PCjr’s oddball keyboard can be a bit of a hassle for vintage computing enthusiasts.

What was strange about the PCjr’s keyboard? From the outside it looked pretty normal, but it definitely had its own thing going on. For one, the PCjr keyboard operated over a completely different protocol than the other keyboards of the time. In addition, its connection to the host was either by IR, or via its own wired cable adapter.

The KeybJr solves this by using an Arduino-based board to turn inputs from other keyboards of the time into something the PCjr expects. These signals are sent out and received either over infrared, or by the PCjr’s “K” port for a wired keyboard link.

Why bother with the IR functionality? Well, the connector and pins on the PCjr are not very rugged, and sometimes they are damaged. In those cases, it is nice to have the option of using a normal (for the time) keyboard over the IR link. Vintage hardware is not always in perfect shape, after all. That’s why things like ATX power supply adapters for the PCjr exist.

Want to give it a shot? There is a GitHub repository for the KeybJr, and you can see it in action in a brief video, embedded below.

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NASA Hardware Techniques: Soldering Space Electronics Like It’s 1958

[PeriscopeFilms] on YouTube has many old TV adverts and US government reels archived on their channel, with some really interesting subjects to dive in to. This first one we’re highlighting here is a 1958 film about NASA Soldering Techniques (Video, embedded below), which has some fascinating details about how things were done during the Space Race, and presumably, continue to be done. The overall message about cleanliness couldn’t really be any clearer if they tried — it’s so critical it looks like those chaps in the film spend far more time brushing and cleaning than actually wielding those super clean soldering irons.

Of particular note are some of the details of wire stripping and jointing with components, such as the use of a hot-wire device to remove the insulation from wire, rather than use the kind of stripper we have lying around that cuts into the insulation and slightly distorts the wire in the process. That just won’t do. If they did have to use a cutting-type stripper, it must be precisely the right size for job, and calibrated daily.

The road to the Moon is paved with calibrated wire strippers.

When soldering a pre-tinned wire to a leaded component, a clamp is required to prevent movement of the wire, as is a thermal shunt on the component lead to protect the delicate component from excess heat. They even specify how much to wrap a wire around a terminal to be soldered, never bending the wire more than 180 degrees.

The bottom line in all this is, is that the work must be as perfect as is possible, as there is very little chance of sending someone up to fix a dodgy soldering job, once the assembly is hurtling around the planet. They call it too much of a science to be called an art and too much art to be called a science, and we can sure appreciate that.

As you would expect (and it’s not exactly a big secret) NASA has some very exacting standards for assembly of all hardware, like this great workmanship standard, which is well worth studying. Soldering is an important subject for many of us, we’ve covered the subject of solder metallurgy, as well as looking at how ancient hardware hackers soldered without the benefit of much modern knowledge.

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Vintage Meter Repair? It’s Easier With X-Rays

Here’s an interesting and detailed teardown and repair of a Keithley 2001 7.5 Digit multimeter that is positively dripping with detail. It’s also not every day that we get to see someone using x-ray imaging to evaluate the extent of PCB damage caused by failed electrolytic capacitors.

Dark area is evidence of damage in the multi-layer PCB.

Sadly, this particular model is especially subject to that exact vintage electronics issue: electrolytic capacitor failure and leakage. These failures can lead to destroyed traces, and this particular unit had a number of them (in addition to a few destroyed diodes, just for good measure.) That’s where the x-ray machine comes in handy, because some of the damage is hidden inside the multi-layer PCBs.

[Shahriar], perhaps best known as [The Signal Path], narrates the entire process of fixing up the high-quality benchtop multimeter in a video, embedded below (or you can skip directly to the x-ray machine being broken out.) [Shahriar] was able to repair the device, thanks in part to it being in relatively good shape, and having the right tools available. Older electronics are not always so cooperative; the older a device is, the more likely one is to run into physical and logical standards that no longer exist.

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