Craig HockenberryThis was unexpected.
(Probably some 40 year old caps releasing their magic smoke.)
Found the culprit at C38. It’s a common fault for the RIFA capacitor that’s made with foil and paper to fail spectacularly due to age.
Thankfully it’s a cheap and easy fix thanks to eBay. I’m going to replace all the capacitors on the analog board as a preventative measure, too. Nothing leaking … yet.
AND EVERY ONE CALLS IT RIFA MADNESS SO THATS JUST A BONUS IF YOU KNOW WHAT I MEAN
This 512k Mac also suffers from another common problem: a floppy drive that won’t eject the disk.
The failure point here is a cog made from a plastic that softens over time. In the image below, you can see how the brass gear has carved out a gap in the teeth of the leftmost cog.
Again, an easy fix with 3D printed parts from eBay.
The best part of opening an original Mac is seeing the signatures of everyone who worked on it.
Sadly, on this second iteration of the Mac (after the original 128k version) some of the names are obscured by some additional plastic. This includes Steve Jobs and Bill Atkinson.
Working with 40 year old plastic is tricky. The only casualty from today’s efforts was the programmer’s switch.
I doubt I’ll be doing any coding on this Mac, but I’ll still replace it for nostalgic reasons. I may even have a spare in my attic!
One more thing:
If you ever plan on opening an old Mac, watch this 10 minute video first.
I could literally save your life.
Discharging the CRT in a compact Macintosh
John Moltz@chockenberry This is the part that has consistently stopped me from opening either of my classic Macs.
@Moltz It’s not that bad once you get the hang of it. And if you haven’t powered the Mac on for awhile, the chances of a residual charge are low.
The video I linked to has complete instructions and lots of hints (use one hand!). Take it slow and carefully and you’ll be fine.
Chris Gervais 🎸🥁💻@Moltz @chockenberry It’s pretty easy to create a discharge cable. However, 12 year old me had zero knowledge of this and was YOLO’ing inside my Mac Plus. But, I’m Gen X so I’ve been through more dangerous situation
@chrisgervais @Moltz 15 year old me saw some doofus in my Electronics class get zapped across the room while digging around in an old TV. I’ve been very careful around the business end of a flyback transformer since then.
Nigel Wadsworth 🇦🇺@chockenberry @chrisgervais @Moltz You can't get your Apple Technician certificate until you've been zapped by a classic Macintosh CRT, an Apple II monitor, *and* some sort of Apple Trinitron-based display. Preferably not a 21-inch colour...
@nygl @chockenberry @Moltz Those big Trinitron displays could power a city with charge stored in their flybacks!
Sean Heber@Moltz @chockenberry if they haven't even been plugged in for years, there's no serious danger - the charge dissipates slowly over time. But that said, it's definitely a good idea to treat CRTs as if they're charged and always go through the motions anyway because they're hella dangerous!
Leigh Caplan@Moltz @chockenberry I cut my teeth as a tech back in the CRT era and they hammered this constantly.
In all my (probably hundreds) of repairs (iMacs, eMacs etc) I don’t think I ever witnessed the telltale “crack!” of a discharge because the bleeder resistors were doing their jobs, but taking shortcuts still wasn’t worth it.
One of the most amusing things was the discharge tool they eventually gave to Mac geniuses in the early 2000s… it was like a 2’ long handle made of plastic with a 6” screw body coming out the end.
We affectionately referred to it as “the cattle prod”
@stevewfolds@chockenberry CRT discharge arced chunks from a screwdriver tip.
Sarah Sammis@chockenberry oh gosh. Memories. I have cracked open my old Mac classic.
Maria Langer | 📝💎🌵🛥️@chockenberry @jcdvore I used to teach folks how to do this as part of a Mac troubleshooting course back in the 1990s.
ChancerubbageI used to get nervous Nellie merely opening my Mac plus to upgrade the ram. Wearing that discharge cuff
I also imagine that extra long torq wrench may not be easy to find these days
🇺🇦 haxadecimal 🚫👑@chockenberry
I've worked on classic CRT Macs a lot, and never discharged the CRT. That's only killed me a few times.
Actually, I never did anything more than pull out the logic board, which, if you're careful about it, doesn't put your hands near any HV. The only problem I ever had was one where a connector was stuck so hard that when it finally let go, my hand flew up and cracked the neck of the CRT, letting the vacuum out. Then you have to replace the CRT, which does require discharging it.
I've worked on classic CRT Macs a lot, and never discharged the CRT. That's only killed me a few times.
Actually, I never did anything more than pull out the logic board, which, if you're careful about it, doesn't put your hands near any HV. The only problem I ever had was one where a connector was stuck so hard that when it finally let go, my hand flew up and cracked the neck of the CRT, letting the vacuum out. Then you have to replace the CRT, which does require discharging it.
Heliograph@chockenberry that little blue bird 😆 ah those were the days...
TheEJJ 🇨🇦@chockenberry what is that sticker on your Mac Mini?
Michael Cook@TheEjj Looks like one of BasicAppleGuy’s “Intel Inside” style stickers for Apple Silicon:
@foobarsoft indeed! Thank you for the link!
@foobarsoft @TheEjj Yep and the 2 is because the Mac Studio reminds me of Thunderbird 2!
@chockenberry Ollie seems quite impressed.
@foobarsoft He keeps me on my toes!
manolo@chockenberry with today's RAM prices i think you might be a billionaire now
@manolo I’m going to buy some Bitcoin when I sell this old Mac!
John Cortexiphan@chockenberry what are you going to do with it all!
Stephen 🦇@chockenberry That’ll be $40million.
Ryan Carver@chockenberry oh this is great to see! I recently got my family’s 128k and am excited and nervous to boot it up.
@chockenberry I wonder if anyone has collected all versions of the signature variations. Here’s mine. Signatures are on the raised bit as well.
@nygl Your part number shows “Rev E” and mine looks like it’s “L”. That’s a pretty good indicator that there are a lot of variations 😉
Also looks like you’ve got a leaky backup battery!
@chockenberry It was a freakin' mess :)
Was a rescue unit. Case says Macintosh 128K. Mainboard was a 512K (Fat Mac). So a late 1984 case, and some crazy person upgraded to 512.
@nygl Ooof - the leakage on the mains input in last photo.
Also wondering if the 240v versions have a different mains connector there (I know the analog boards are different).
@chockenberry Yes, I bought a re-cap kit for it, but the more I look at it the more worried I am about traces and other components.
Dave Nanian@chockenberry I realize this isn't Mac-related, but one of the big differences between "old" B&O turntables and "newer" ones involves replacing cast and machined parts with plastic.
The old ones (like the Beogram 4000) need restoration, but are generally fine after 50 years (usually, as in your case, failures involve caps).
The newer ones (like the Beogram 8002) suffer from plastic that's become brittle and must be replaced with 3D parts.
All too endemic...