Re-Capping An Ancient Apple PSU

It sometimes comes as a shock when you look at a piece of hardware that you maybe bought new and still consider to be rather high-tech, and realise that it was made before someone in their mid-twenties was born. It’s the moment from that Waylon Jennings lyric, about looking in the mirror in total surprise, hair on your shoulders and age in your eyes. Yes, those people in their mid-twenties have never even heard of Waylon Jennings.

[Steve] at Big Mess o’Wires has a Mac IIsi from the early 1990s that wouldn’t power up. He’d already had the life-expired electrolytic capacitors replaced on the mainboard, so the chief suspect was the power supply. That miracle of technology was now pushing past a quarter century, and showing its age. In case anyone is tempted to say they don’t make ’em like they used to, [Steve]’s PSU should dispel the myth.

It’s easy as an electronic engineer writing this piece to think: So? Just open the lid, pop out the old ones and drop in the new, job done! But it’s also easy to forget that not everyone has the same experiences and opening up a mains PSU is something to approach with some trepidation if you’re not used to working with line power. [Steve] was new to mains PSUs and considered sending it to someone else, but decided he *should* be able to do it so set to work.

The Apple PSU is a switch-mode design. Ubiquitous today but still a higher-cost item in those days as you’ll know if you owned an earlier Commodore Amiga whose great big PSU box looked the same as but weighed ten times as much as its later siblings. In simple terms, the mains voltage is rectified to a high-voltage DC, chopped at a high frequency and sent through a small and lightweight ferrite-cored transformer to create the lower voltages. This means it has quite a few electrolytic capacitors, and some of them are significantly stressed with heat and voltage.

Forum posts on the same PSU identified three candidates for replacement – the high voltage smoothing capacitor and a couple of SMD capacitors on the PWM control board. We’d be tempted to say replace the lot while you have it open, but [Steve] set to work on these three. The smoothing cap was taken out with a vacuum desoldering gun, but he had some problems with the SMD caps. Using a hot air gun to remove them he managed to dislodge some of the other SMD components, resulting in the need for a significant cleanup and rework. We’d suggest next time forgoing the air gun and using a fine tip iron to melt each terminal in turn, the cap only has two and should be capable of being tipped up with a pair of pliers to separate each one.

So at the end of it all, he had a working Mac with a PSU that should be good for another twenty years. And he gained the confidence to recap mains power supplies.

If you are tempted to look inside a mains power supply you should not necessarily be put off by the fact it handles mains voltage as long as you treat it with respect. Don’t power it up while you have it open unless it is through an isolation transformer, and remember at all times that it can generate lethal voltages so be very careful and don’t touch it in any way while it is powered up. If in doubt, just don’t power it up at all while open. If you are concerned about high voltages remaining in capacitors when it is turned off, simply measure those voltages with your multimeter. If any remain, discharge them through a suitable resistor until you can no longer measure them. There is a lot for the curious hacker to learn within a switch mode PSU, why should the electronic engineers have all the fun!

This isn’t the first recapping story we’ve covered, and it will no doubt not be the last. Browse our recapping tag for more.

Don’t Tempt the Demo Gods

Including a live technical demonstration as part of a presentation is a lot like walking a tightrope without a net. Which isn’t to say that we don’t do it — we just keep our fingers crossed and bring our lucky horseshoe. The demo gods have smote [Quinn] a mighty blow, in front of a class at Stanford, no less.

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[Quinn]’s scratch-built computer, Veronica, failed to boot in front of a hall of eager students. When the pressure was off, in the comfort of her own lab, [Quinn] got to debugging. You should read her blog post if you’re at all interested in retrocomputing or troubleshooting of low-level hardware bugs. But if you just can’t spare the five minutes for a pleasant read, here’s a spoiler: watch out for flaky card-edge connectors. All’s well that ends well, with a game of pong.

We’ve been following Veronica from her very first clock cycles, so we’re happy to see her back on her feet again. Good job, [Quinn]!

From Trash To TV

In days gone by, when TVs had CRTs and still came in wooden cabinets, a dead TV in a dumpster was a common sight. Consumer grade electronic devices of the 1960s and ’70s were not entirely reliable, and the inside of a domestic TV set was not the place for them to be put under least stress. If you were electronic-savvy you could either harvest these sets as a source of free components, or with relative ease fix them for a free TV set.

With today’s LCDs, integrated electronics, and electronic waste regulations, the days of free electronics in every dumpster are largely behind us. Modern TVs are more reliable, and when they reach end-of-life we’re less likely to see them.

[Sidsingh] happened to find an LCD TV in a dumpster, and being curious as to whether he could fix it or salvage some components, cracked it open to take a look.

He found that somebody had already been into the set and that some components on the PSU and backlight boards showed evidence of magic smoke escaping, having been desoldered by the previous repairer. The signal board was intact though, a generic Chinese model based around a Mediatek MTK8227 SoC. Information was scarce on these boards, but some patient research yielded a schematic for a similar set.

Once he knew more about the circuit, he was able to identify the power lines and discovered that the 1.8v line to the SoC was faulty. This he traced to a switching regulator for which there was no equivalent in his junkbox, so he substituted a linear regulator to obtain the required voltage. The CFL backlight was then removed and replaced with LED strips, and as if by magic he had a working TV set.

This might seem a relatively mundane achievement on the scale of some of the projects we feature on these pages, but it is an important one. In these days of throwaway items it is still not impossible to repair dead electronic devices, indeed as [Sidsingh] found the power supply is most likely to be the culprit. If you score a dead LCD TV then don’t be afraid to crack it open yourself, you may be able to fix it.

As you might imagine, many repairs have made it onto Hackaday over the years. Of relevance to this one is this LCD that inexplicably worked when exposed to light, an LED backlight conversion, and this capacitor swap to return an LCD monitor to health.

1921 Ner-A-Car Motorcycle Reborn With Epic Parts Remanufacture

Most of the rusty parts you need to make a motorcycle.
Most of the rusty parts you need to make a motorcycle.

Nobody ever dismantles a working motorcycle.

About ten years ago [Andy Pugh] took possession of a large box of rusty parts that formed most of what had once been a 1921 Ner-a-Car motorcycle. They languished for several years, until in 2014 he was spurred into action and returned to the bike. What followed was a two-year odyssey of rebuilding, restoration, and parts remanufacture, and since [Andy] is an engineer par excellence and an active member of the LinuxCNC community his blog posts on the subject should be a fascinating read for any hardware hacker with an interest in metalwork.

The Ner-a-Car. By Museumsfotografierer (Own work) [Public domain], via Wikimedia Commons
The Ner-a-Car. By Museumsfotografierer (Own work) [Public domain], via Wikimedia Commons
The Ner-a-Car represents one of those eccentric dead-ends in automotive history. Designed in 1918 by an American, [Carl Neracher], its name is a play on both its designer and its construction and it is unique in that its design is closer to the cars of the era than that of a motorcycle. It has a car-style chassis, an in-line engine, and it was the first motorcycle to be produced with hub-centre steering. The rider sits on it rather than astride it, feet-forward, and the car-style chassis gives it a very low centre of gravity. They were manufactured in slightly different versions in both the USA and the UK, and [Andy]’s machine is an early example from the British production line. Not many Ner-a-Cars have survived and parts availability is non-existent, so his work has also had the unusual effect of satisfying a significant portion of world demand for the parts-bin of an entire marque.

Spinning up a headlight shell
Spinning up a headlight shell

It’s usual for the first link in a Hackaday article to be to a page that encompasses the whole project. In this case when there is so much to see and the build is spread across twelve blog posts and nearly two years the link is to [Andy]’s first post in which he describes the project, sets to work on the chassis, and discovers the bent steering arm that probably caused the bike’s dismantling. He’s listed the posts in the column on the right-hand side of the blog, so you can follow his progress through the entire build. The work involved in remanufacturing the parts is to an extremely high standard, from machining press tools to reproduce 1920s footboard pressings through manufacturing authentic 1920s headlight switchgear and metal-spinning new aluminium headlight shells.

[Andy]’s most recent Ner-a-Car post details his trip to France on the completed bike, and tales of roadside repairs of a suddenly-not-working machine that should be familiar to any owner of a vintage internal combustion engine. But considering that the bike spent many decades as a pile of not much more than scrap metal the fact that it is now capable of a trip to France is nothing short of amazing.

This is the first rebuild of a vintage bike from a box of rusty parts we’ve featured here – indeed it could almost be a retrotechtacular piece in its detailed look at 1920s bike design. These pages have however seen many motorcycle related  hacks over the years. We particularly like this from-scratch engine build and this gas-turbine bike, but it is the emergency motorcycle build in the desert from a Citroën 2CV car that has us most impressed. Please, ride safe, and keep them coming!

Fail Of The Week: Always Check The Fuse

[Tomas] at Umeå Hackerspace in Sweden had some broken audio equipment, including a Sharp CD player/amplifier. What went wrong when he tried to fix it is a fail story from which we can all learn.

The device worked – for about a second after being turned on, before turning itself off. That’s a hopeful sign, time to start debugging. He took the small-signal and logic boards out of the circuit, leaving only power supply and amplifier, and applied the juice.

Magic blue smoke ensued, coming from the amplifier. Lacking a suitable replacement part, that was it for the Sharp.

On closer inspection it emerged that the previous owner had bypassed the power supply fuse with a piece of copper wire, Evidently they had found the fuse to be blowing too often and instead of trying to fix the problem simply shot the messenger.

We have all probably done it at some time or other. In the absence of a replacement fuse we may have guestimated the number of single strands required to take the current, or used a thin strip of foil wrapped around the fuse body. And we’ll all have laughed at that meme about using a spanner or a live round as a fuse.

So if there’s a moral to this story, it’s to always assume that everyone else is as capable as you are of doing such a dodgy fix, and to always check the fuse.


2013-09-05-Hackaday-Fail-tips-tileFail of the Week is a Hackaday column which celebrates failure as a learning tool. Help keep the fun rolling by writing about your own failures and sending us a link to the story — or sending in links to fail write ups you find in your Internet travels.

Tearing Down an IP Camera

So you bring home a shiny new gadget. You plug it into your network, turn it on, and it does… well, whatever it wants. Hopefully, it does what you expect and no more, but there is no guarantee: it could be sending your network traffic to the NSA, MI5 or just the highest bidder. [Jelmer] decided to find out what a new IP camera did, and how easy it was to find out by taking a good poke around inside.

In his write-up of this teardown, he describes how he used Wireshark to see who the camera was talking to over the Interwebs, and how he was able to get root access to the device itself (spoilers: the root password was 1234546). He did this by using the serial interface of the Ralink RT3050 that is the brains of the camera to get in, which provided a nice console when he asked politely. A bit of poking around found the password file, which was all too easily decrypted with John the ripper.

This is basic stuff, but if you’ve never opened up an embedded Linux device and gotten root on it, you absolutely should. And now you’ve got a nicely written lesson in how to do it. Go poke around inside the things you own!

SATA Cable Replaces DC Motor Brushes as Macgyver Looks On

[dmalhar] was digging around in his bins for motors and found one with missing brushes. Being resourceful (and not able to find another motor), he managed to tear apart a SATA cable and form the pins into brushes with just the right amount of spring. Yes, this looks like a cheap motor, but in the moment of necessity availability wins, and this hack is truly commendable. If he had used a paperclip, MacGyver would have been proud, but the SATA cable pins make us proud.

Normally the brushes of DC motors are made with a graphite or some other material which provides a small amount of resistance so that when the motor is spinning the brushes will provide a gradual shift of current from one commutator to the next. Also, the softness of the carbon makes the brush wear down instead of the commutator, and in large motors the brushes are replaceable. In cheap motors the engineers design the brush material around the expected lifetime of the product. In [dmalhar’s] case, the motor just got its lifetime extended by a while.