A Deep Dive Into The Sound Of An Apple II

October 14, 2021 by 21 Comments

A major part of the retrocomputing scene for many of us lies in the world of chiptunes, music created either using original retrocomputing hardware or in the style of those early synthesiser chips. There’s one machine we don’t hear much about among all this though, and that’s the Apple II. Though probably one of the most expandable of all the 8-bit home computers, it lacked a sound channel beyond a speaker hooked up to a memory location port so any complex sound work had to be done via an add-on card. It’s something [Nicole Branagan] has investigated in depth, as she demonstrates first the buzz from the speaker and then what must have been an object of extreme desire back in the day, a Mockingboard sound card.

Her card is not an original but a modern recreation using the same hardware, which is to say a pair of 6522 VIA port chips, each driving an AY-3-8910 audio chip. This is already a familiar device to those who have heard an Amstrad CPC, a later Sinclair Spectrum or, an MSX, and in the Apple it delivers an impressive stereo sound thanks to both channels being present. Interestingly though, it delivers a far smoother output than an MSX playing the same music, probably because of a superior filtering circuit.

She wraps up with a discussion of coding on the Apple for the AY, and how to best accommodate the card on the later Apple IIgs. If the AY chip catches your interest, it’s also easy to drive from a microcontroller.

Spilled OJ Does A Number On Zelda Game Boy Cartridge

October 13, 2021 by 16 Comments

When [Taylor Burley] first opened up the cartridge for The Legend of Zelda: Oracle of Seasons, it certainly didn’t look like it had been dunked in corrosive orange juice. But looks can be deceiving, and while the game’s owner certainly did an admirable job of cleaning up the surface of the PCB, the cartridge was no longer functional. Clearly, this was a sticky situation.

After removing all of the components from the PCB, [Taylor] was quickly able to piece together what had happened. Despite the vigorous cleaning the game received after the spill, juice had found its way under each IC on the board. Left to sit in these nooks and crannies for who knows how long, the juice started to eat away at the traces on the PCB. Getting the game back up and running would naturally require considerable board repairs, but they don’t call him Solderking for nothing.

Corrosion lurking under each chip.

In the video below, you can see [Taylor] methodically scraping away the corrosion on the board before he starts recreating damaged connections with solid 30 gauge wire. Using tweezers and viewing the action through a digital microscope, he deftly bends the wire around to fit the shapes of the original traces and tacks the new conductors down with solder. He even goes ahead and repairs the traces that go to various test points on the cartridge; it’s a completely unnecessary extravagance, but we’re certainly not complaining. There’s a relaxing quality to watching him work, so we were in no rush to see his latest video end.

After fixing the board back up, he replaces all the components and takes it for a test drive on an original Game Boy Color. Confirming that Link’s 2001 outing is working as expected, he finishes the job with a few coats of spray-on conformal coating. With any luck, the next time this particular cartridge has to go face-to-face with some spilled juice, it will roll right off.

This isn’t the first time we’ve seen [Taylor] laboriously rebuild a Game Boy cartridge, and it certainly isn’t the first time we’ve seen him pull off some particularly impressive feats of soldering, either. His work always reminds us that patience and a steady hand can really do wonders.

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Solar Power Goes Back To 1910 Tech

October 13, 2021 by 41 Comments

If you want to read about a low-tech approach to solar cells invented — and forgotten — 40 years before Bell Labs announced the first practical silicon solar cell, we can’t promise the website, Low Tech Magazine, will be available. Apparently the webserver it is on is solar-powered, and a disclaimer mentions that it sometimes goes offline.

The article by [Kris De Decker] tells of George Cove and includes a picture from 1910 of the inventor standing next to what looks suspiciously like a solar panel (the picture above is from a 1909 issue of Technical World Magazine). His first demonstration of the technology was in 1905 and there is a picture of another device from 1909 that produced 45 watts of power using 1.5 square meters with a conversion efficiency of 2.75%. That same year, a new prototype had 4.5 square meters and used its 240-watt output to charge 5 lead-acid batteries. The efficiency was about 5%.

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PCB sitting inside a 3D printed holder job, with holes to apply vacuum

Solder Paste Stencilling That Doesn’t Suck

October 13, 2021 by 7 Comments

Working with solder paste stencils can be a real faff, they rarely sit flat and move around when you so much as breath on them. [Unexpected Maker] airs his frustrations, and comes up with a simple solution, he simply makes a 3D-printed jig to align the PCB panel and applies his shop vacuum cleaner and hey presto!

If you’re ever been tempted to switch from frameless to framed solder stencils, then you’ll notice they can be rather awkward to work with. The usual online vendors have plenty of listings for stencil frame holders, but they do all seem to us, exactly the same, and more suited to stencilling T-shirts, than working with tiny PCB footprints.

The problem with unframed stencils is one of clamping and registration to the PCB, which framed stencils fix, when used with a jig that can dial in the rotation and translation errors.

But problem with those is, unless you have a perfectly flat support region all round the PCB, the weight of the frame tends to make the stencil bow up over the PCB, causing parts of it to lift away from the solder lands. This results in paste not being pushed into the places you want it, and instead it sticks to the stencil apertures and comes away when you lift it up. Most irritating.

You can try offset it by taping spare PCBs of the same thickness all around, but this is not always terribly successful in this scribe’s extensive experience doing this job by hand. [Unexpected Maker] solves this bowing issue by making a 3D printed jig that bolts to the stencil holder, takes a custom top plate with holes in, which in turns allows a vacuum to be applied from below. This sucks the PCB down to the jig, keeping it flat (in case it is also warped) and also pulls the stencil plate directly down to the PCB, making it also lie perfectly flat.

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A tiny TV that shows weather, news, and the classic test pattern.

Tiny TV Tells The Temperature Tale

October 13, 2021 by 3 Comments

Once upon a time, we would run home from the bus stop to watch Gargoyles and Brady Bunch reruns on the family TV, a late-1970s console Magnavox number that sat on the floor and was about 50% more cabinet than CRT. The old TV, a streamlined white Zenith at least ten years older, had been relegated to the man cave in the basement. It looked so mod compared to the “new” TV, but that’s not the aesthetic my folks were after. They wanted their electronics to double as furniture.

This little TV is a happy medium between the two styles, and for us, it’s all about those feet. But instead of cartoons, it switches between showing the current weather and the top news headlines. Inside that classy oak cabinet is an LCD, an ESP32, and an SD card module. The TV uses OpenWeatherMap and pulls the corresponding weather image from the SD card based on time of day — light images for day, and dark images for night.

We love that it shows the SMPTE color bars, aka the standard American TV test pattern as it switches between weather and news. After showing the top headlines, it automatically switches back to the weather channel. Be sure to check out the short demo video after the break.

Do you like your tiny televisions in strange places? Here’s one you can use to trim your tree this year.

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G10 Is The 3D Print Surface You Crave

October 13, 2021 by 49 Comments

Print surfaces have been a major part of 3D printer development and experimentation since the beginning. [Makers Muse] has been experimenting with G10, a cheap high-pressure fiberglass laminate, and found that it’s an excellent candidate for most of your FDM printing needs. (Video embedded after the break.)

You’re probably more familiar with the fire-resistant version of G10, FR-4, the fiberglass substrate used for most PCBs. It’s also known by the brand name Garolite. [Makers Muse] tested with PLA, PETG (on his headphone build), ABS, ASA, PET, PCTG, and nylon. All the materials displayed excellent bed adhesion when heated to the appropriate temperature, and would often self-release the part as it cooled down. For TPU, the bed was left unheated to prevent it from sticking too well. 0.5 mm, 1.5 mm, and 3 mm G10 sheet thicknesses were tested, and [Makers Muse] found 1.5 mm to be the perfect balance between rigidity, and flexibility for removing particularly sticky prints.

G10 has been used in some commercial 3D printers, but there is very little information regarding its use beyond high-temperature materials like nylon. It leaves an excellent surface finish on the bottom of parts, as long as you take care not to scratch the bed. Compared to glass, its lower weight is advantageous for printers where the bed moves for the Y-axis. Another major advantage is the low cost, especially compared to some of the more exotic bed materials.

The results certainly look very promising, and we are keen to get our hands on some G10 for our own printers. If you have trouble finding it for sale, check out your local knife-making suppliers, who sell it as handle materials.

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Space Age Road Rage: Right Of Way Above The Karman Line

October 13, 2021 by 35 Comments

On a dark night in 2006 I was bicycle commuting to my office, oblivious to the countless man made objects orbiting in the sky above me at thousands of miles per hour. My attention was instead focused on a northbound car speeding through a freeway underpass at dozens of miles per hour, oblivious to my southbound headlamp. The car swerved into the left turn lane to get to the freeway on-ramp. The problem? I was only a few feet from crossing the entrance to that very on-ramp! As the car rushed through their left turn I was presented with a split second decision: slow, and possibly stop in the middle of the on-ramp, or just go for it and hope for the best.

A graphic depicting a dawdling bicycle rider about to be in the way of a speeding car driver
In Blue: Terrified cyclist. In Red: A speeding car careening around a corner without slowing down.

By law I had the right of way. But this was no time to start discussing right of way with the driver of the vehicle that threatened to turn me into a dark spot on the road. I followed my gut instinct, and my legs burned in compliance as I sped across that on-ramp entrance with all my might. The oncoming car missed my rear wheel by mere feet! What could have ended in disaster and possibly even death had resulted in a near miss.

Terrestrial vehicles generally have laws and regulations that specify and enforce proper behavior. I had every right to expect the oncoming car be observant of their surroundings or to at least slow to a normal speed before making that turn. In contrast, traffic control in Earth orbit conjures up thoughts of bargain-crazed shoppers packed into a big box store on Black Friday.

So is spacecraft traffic in orbit really a free-for-all? If there were stringent rules, how can they be enforced? Before we explore the answers to those questions, let’s examine the problem we’re here to discuss: stuff in space running into other stuff in space.

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