Resurrecting a Macintosh Plus from the dustbin

Stuart Cording, an Atmel aficionado over in Europe, tipped me off to this blog where a fellow got his old Mac Plus up and running. Jeff Keacher had the typical hardware problem, a power supply capacitor blew on him after a short while. What was amazing is he also got it to connect to the World Wide Web.


Jeff Keacher got this 27-year-old Macintosh computer up and running and then got it to browse the web.

My buddy Alan Martin over at honored competitor Texas Instruments has a saying “It’s always a cap”. With old radios and such it is the large can electrolytic that dry out. They stop filtering the wall voltage so you then hear a bad hum in the output. Eventually they “punch through” and blow up. For test equipment, Alan often comments on how great it was that Tektronix used all those “lemon drop” tantalum capacitors, since they all fail and make it easy to buy really good test equipment really cheap. Then you just replace all the tantalum and electrolytic capacitors. Like the old Macintosh, you can always find a suitable replacement at Digi-Key, or one of the other distributors. I have described how Eric Schlaepfer over at Google manages to put a new capacitor in the original can, so the gizmo still has that classic vintage took to it.


This is the X-rated capacitor that failed in the Mac Plus.

The cap in the Mac was an X-cap, a film capacitor that is rated for long life and designed to be across line voltage, the 120AC in your house. It is a little disturbing that it failed, film caps don’t dry out like electrolytic. I know some of my pals use a Variac to slowly bring up the line voltage the first time they power up old equipment. I hear that doing that is less stressful to the capacitors and you can see things smoking at a lower voltage so you might not do as much damage.


My analog aficionado pals bring up old equipment with a variac like this. That way you are applying voltage to the input capacitors with a slow ramp-up.

Now there was quite a hardware and software challenge to get the Mac Plus on the web. I think it was a bit of a cheat to use a Raspberry pi. Heck the pi will run Linux and has a video system. Why not just toss the Mac Plus in the garbage and connect a monitor the Raspberry pi? Well, sure, anybody can do that. So the author solved the hardware problem letting a Raspberry Pi be the middle-ware between the Mac and the Web. But there was still plenty of fun putting in a TCP/IP stack and a browser and all the other fun coding they had to do to get a web page to render. Bravo, now I think I will listen to that Merle Haggard song about Fords and Chevys lasting ten years like they should.

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