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.

Hackaday Links: January 31, 2016

[Damien] has been working on MicroPython for a while now. We did an interview with him a while ago about porting Python to tiny microcontrollers, and soon the BBC micro:bit will be getting Python into the hands of millions of British schoolchildren. Now [Damien] has a Kickstarter to get MicroPython to the bare metal of an ESP8266. That would be extremely interesting; there’s a lot you can do with an easily scriptable Internet Thing running Python.

A little over a month ago, [Renier] won the Hackaday Prize Best Product competition with the Vinduino, a device that cuts water usage of vinyards (and orchards, I guess) by 25%. Now he’s won the IoT awards for Best DIY Project.

We have lost a great inventor. [Artur Fischer], inventor of the plastic drywall plug, fischertechnik, the plastic wall plug, photo flash light, and holder of over 1100 patents (more than the great Edison), passed away this week.

Who remembers Glider? That old Macintosh game where you fly a paper airplane around a house is now available on GitHub. The creator of Glider, [John Calhoun] put all the code up a few days ago. If you have Metrowerks Code Warrior sitting around on an old box, feel free to dig around.

 In the ‘this guy totally won’t get sued’ column is MagSafe for iPhones. The MagSafe power adapter is Apple’s largest contribution to humanity, but they are a little protective about it.

We have two calls for the community: [jimie] had a go at programming the latest, coolest, open source radio. Programming it is hard. Has anyone found an improved guide? Second, I now have a Tadpole Computer that was former property of Quallcom. I can’t find any info on getting *nix or *BSD on it. Anyone have any experience?

Better Networking With A Macintosh Classic

While it may not be the case anymore, if you compare a Mac and a PC from 1990, the Mac comes out far ahead. PCs suffered with DOS, while the Mac enjoyed real, non-bitmapped fonts. Where a Windows PC required LANMAN to connect to a network, the Mac had networking built right into every single machine. In fact, any Mac from The Old Days can use this built-in networking to connect to the Internet, but most old Mac networking hacks have relied on PPP or other network to serial conversion. [Pierre] thought there was an incomplete understanding in getting old Macs up on the Internet and decided to connect a Mac Classic to the Internet with Apple’s built-in networking.

Since the very first Macintosh, Apple included a simple networking protocol that allowed users to share hard drives, folders, and printers over a local network. This networking setup was called LocalTalk. It wasn’t meant for internets or very large networks; the connection between computers was basically daisy chained serial cables and later RJ-11 (telephone) cables.

LocalTalk stuck around for a long time, and even now if you need to do anything with a Mac made in the last century, it’s your best bet for file transfer. Because of LocalTalk’s longevity, routers and LocalTalk to Ethernet adapters can be found fairly easily. The only problem is finding a modern device that speaks both TCP/IP and LocalTalk. You can’t use a new Mac for this; LocalTalk has been gone from OS X since Snow Leopard. You can do it with a Raspberry Pi, though.

With a little bit of futzing about with MacTCP and a few other pieces of software from 1993 or thereabouts, [Pierre] can even get his old Mac Classic online. Of course the browsers are all horribly outdated (making the Hackaday retro edition very useful), but [Pierre] was able to load up It takes a while with an 8MHz CPU and 4MB of RAM, but it does get the job done.

You can check out [Pierre]’s demo video below.

Continue reading “Better Networking With A Macintosh Classic”

Hackaday Links: October 25, 2015

There are dozens of different 3D printable cases out there for the Raspberry Pi, but the BeagleBone Black, as useful as it is, doesn’t have as many options. The folks at 3D hubs thought they could solve this with a portable electronics lab for the BBB. It opens like a book, fits a half-size breadboard inside, and looks very cool.

The guy who 3D printed his lawnmower has a very, very large 3D printer. He now added a hammock to it, just so he could hang out during the very long prints.

There’s a box somewhere in your attic, basement, or garage filled with IDE cables. Wouldn’t they be useful for projects? Yep, only not all the wires work; some are grounds tied together, some are not wired straight through, and some are missing. [esot.eric] has the definitive guide for 80-wire IDE cables.

Like case mods? Here’s a golden apple, made out of walnut. Yes, there are better woods he could have used. It’s a wooden replica of a Mac 128 with a Mac Mini and LCD stuffed inside. Want a video? Here you go.

If you have a 3D printer, you’re probably familiar with PEEK. It’s the plastic used as a thermal break in non-all-metal hotends. Now it’s a filament. An extraordinarily expensive filament at €900 per kilogram. Printing temperature is 370°C, so you’ll need an all-metal hotend.

It’s the Kickstarter that just keeps going and going and going. That’s not a bad thing, though: there really isn’t much of a market for new Amiga 1200 cases. We’ve featured this project before, but the last time was unsuccessful. Now, with seven days left and just over $14k to go, it might make it this time.

Macintosh Hard Drive Repair

The Macintosh II was a popular computer in the era before Apple dominated the coffee shop user market, but for those of us still using our Mac II’s you may find that your SCSI hard drive isn’t performing the way that it should. Since this computer is somewhat of a relic and information on them is scarce, [TheKhakinator] posted his own hard drive repair procedure for these classic computers.

The root of the problem is that the Quantum SCSI hard drives that came with these computers use a rubber-style bump stop for the head, which becomes “gloopy” after some time. These computers are in the range of 28 years old, so “some time” is relative. The fix involves removing the magnets in the hard drive, which in [TheKhakinator]’s case was difficult because of an uncooperative screw, and removing the rubber bump stops. In this video, they were replaced with PVC, but [TheKhakinator] is open to suggestions if anyone knows of a better material choice.

This video is very informative and, if you’ve never seen the inside of a hard drive, is a pretty good instructional video about the internals. If you own one of these machines and are having the same problems, hopefully you can get your System 6 computer up and running now! Once you do, be sure to head over to the retro page and let us know how you did!

Continue reading “Macintosh Hard Drive Repair”

A Third Scale Mini PowerMac

We’re surrounded by tiny ARM boards running Linux, and one of the most popular things to do with these tiny yet powerful computers is case modding. We’ve seen Raspberry Pis in Game Boys, old Ataris, and even in books. [Aaron] decided it was time to fit a tiny computer inside an officially licensed bit of miniature Apple hardware and came up with the Mini PowerMac. It’s a 1/3rd scale model of an all-in-one Mac from 1996, and [Aaron] made its new hardware fit like a glove.

Instead of an old Mac modified with an LCD, or even a tiny 3D printed model like Adafruit’s Mini Mac Pi, [Aaron] is using an accessory for American Girl dolls released in 1996. This third-scale model of an all-in-one PowerPC Mac is surprisingly advanced for something that would go in a doll house. When used by American Girl dolls, it has a 3.25″ monochrome LCD that simulates the MacOS responding to mouse clicks and keypresses. If you want to see the stock tiny Mac in action, here’s a video.

The American Girl Mini Macintosh is hollow, and there’s a lot of space in this lump of plastic. [Aaron] tried to fit a Raspberry Pi in the case. A Pi wouldn’t fit. An ODROID-W did, and with a little bit of soldering, [Aaron] had a computer far more powerful than an actual PowerMac 5200. Added to this is a 3.5″ automotive rearview display, carefully mounted to the 1/3rd size screen bezel of the mini Mac.

The rest of the build is exactly what you would expect – a DC/DC step down converter, a USB hub, and a pair of dongles for WiFi and a wireless keyboard. The software for the ODROID-W is fully compatible with the Raspberry Pi, and a quick install of the Basilisk II Macintosh emulator and an installation of Mac OS 7.5.3 completed the build.

Viewing A Macintosh SE’s Video On A Modern Computer

[Bbraun] has an old Macintosh SE computer. He was looking for a way to view the video output from the SE on a newer, modern computer. He ended up working out a pretty clever solution using a stm32f4discovery board.

First, the SE’s logic board was removed from its case and placed onto a desk for easier access. The discovery board was then hooked up to the SE’s processor direct slot (PDS) using normal jumper wires. The discovery board acts as a USB COM port on a newer Mac OSX computer. The discovery board watches the SE for writes to video memory. When it sees that the R/W pin goes low, it knows that a write is occurring. It then waits for /AS to go low, which indicates that an address is on the bus. The discovery board reads the address and verifies that it falls within the range of the video frame buffer. If it does, then the discovery board writes a copy of the data to a local buffer.

The OSX computer runs a simple app that can make a request to the discovery board via USB. When the board receives the request, it sends its local frame buffer data over the USB connection and back to the host. The OSX computer then displays that data in a window using CGImage. The demo video below was captured using this technique. Continue reading “Viewing A Macintosh SE’s Video On A Modern Computer”