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Macintosh Classic II Repair — Part 2

September 8, 2023

Part 1

Part 2: You are here

Part 3 (Final)

Written on a MacBook Pro while listening to Sardonicast.

Continued from Part 1, linked above.

So despite my prediction:

Mouser is very fast to ship so luckily I think the parts will arrive first, followed by the keyboard & mouse, and I expect the Wombat will doddle since it's not made or shipped by Professional BigCorp.

the keyboard & mouse arrived first, followed by the Wombat, with the capacitors dilly dallying until Wednesday (the 6th). I was surprised they bothered shipping the Wombat over labor day weekend, but they did so it arrived in typical USPS punctual fashion. Turns out that UPS, that Mouser uses to ship, don't work over labor day to clarify, I'm not upset about that so it didn't get sorted or go out for delivery until Wednesday. Luckily I had all afternoon free and they arrived early-ish, so I had plenty of time to work before needing to drop everything for while—time which it unexpectedly turned out I needed.

First, upon opening the package it turns out I ordered the right PRAM battery, but this one had solder tabs welded on instead of being a normal battery the opposite of my normal problem with batteries lol.

The original PRAM battery next to the new one. They're both nearly identical half-AA lithium cells by the same manufacturer, but the new one has long metal solder tabs spot welded on the terminals so you could solder it into something.The original PRAM battery next to the new one. They're both nearly identical half-AA lithium cells by the same manufacturer, but the new one has long metal solder tabs spot welded on the terminals so you could solder it into something.

Luckily the tabs were just light spot welds so they pop right off. Magically, everything else that I ordered seemed spot on. Time to move onto recapping the logic board, just replacing seventeen capacitors, somewhat tight together but still reachable with the iron, no biggie.

Recapping

To preface this section, I'm gonna say that halfway through the four hour process I dropped everything and angrily posted this on the Fediverse:

I am now convinced Apple is literally the worst hardware manufacturer to ever exist on this planet.

This was the most frustrating and arduous soldering job I've ever done. Despite having my soldering iron at barely the melting point for leaded solder, every single time I removed a capacitor, I had at least one of the pads begin to lift; and three pads overall completely lifted and broke the traces. While my Fedi post blamed Apple—who are partially responsible because of the insanely tiny, SMD pads for the smaller caps—I think now it was actually because the capacitor goop had partially or entirely eaten whatever adhesive stuck the copper to the board. I noticed that one began lifting before I had even heated it, just heating the other and slightly wiggling the cap started moving the other pad so most were already not adhered before I got to them. Luckily only three actually broke and I was able to actually get the original pads reconnected to the traces. But to avoid breaking any more, removing each cap was very, very painstaking, and I was exceptionally careful soldering the new ones on as well. Hence it taking almost four hours total, or nearly fifteen minutes per capacitor, albeit not accounting for the hour total spent getting the broken pads reconnected, and then trying to get the caps attached without re-breaking the traces.

After finally getting them all replaced, I double- and triple-checked the continuity on all the caps to the directly connected via(s) and IC pins, and quadruple-checked the continuity on the lifted pads, everything looking functional. Hopeful that was it, I popped the logic board back in, and… still checkerboard :( At least I didn't completely destroy the computer, and this time I did actually hear the hard drive seek around a bit! So there's still some hope, but I had some schoolwork to do I'd put off when the caps arrived and the recapping was so exhausting, so I let it be until yesterday.

Cleaning, The Other Parts

Yesterday I unexpectedly had some time so I decided to work on the computer a bit. I started by just pouring isopropyl alcohol on the logic board and scrubbing a bit with q-tips, to remove any rosin flux from my soldering and to clean up the capacitor juice that I hadn't cleaned while recapping. People often recommend actually scrubbing boards with soap and water, or even using the dishwasher(!), but with my job on the lifted pads I'm handling it with extreme care. Maybe I should glue them down once I'm sure I'm done poking at them…

Letting that sit to dry, I started trying to extract the analog board. It's heavily interconnected into everything else (doubling as a power supply) but after slicing through some adhesive holding the neck board to the CRT I was able to extricate it.

I like this little touch on the CRT's neck board that they then covered up with a much more boring paper warning labelI like this little touch on the CRT's neck board that they then covered up with a much more boring paper warning label

The analog board, with the permanent wires leading to the molex power/data connector on the logic board, the wires running to the CRT neck board, and the wire from the flyback transformer to the CRT anode suction cup.The analog board, with the permanent wires leading to the molex power/data connector on the logic board, the wires running to the CRT neck board, and the wire from the flyback transformer to the CRT anode suction cup.

I did the most thorough visual inspection I possibly could, completely dusting the board and using a bright penlight to check the entire outside of every individual component, with no capacitor leakage or anything else visible. If there's anything wrong with the board I have no clue what it is.

At that stage I decided to finish removing the CRT, hard drive, and floppy drive so I could completely wash the case. With all the connectors off of it I went for the CRT, and was rather shocked that the only thing holding it in place was screws driven into the plastic front shell; I hadn't noticed that it wasn't attached to the metal frame the rest of the cards were in at all. Maybe this was deliberate to try and avoid it touching the ground plane, but it still seems questionable to have this big glass thing hanging over all the other components, mounted solely on plastic.

Removing the hard drive and floppy drive was trivial, as was getting them out of their cages. On my checklist in Part 1 I wanted to check the FDD belt, and I was surprised that it actually seems to be direct drive:

A large circular magnet on the bottom of the floppy drive with electromagnet coils visible around the edges. It was directly attached to the spindle when I had the drive out of the cage.A large circular magnet on the bottom of the floppy drive with electromagnet coils visible around the edges. It was directly attached to the spindle when I had the drive out of the cage.

Finally, I literally hosed down the case and metal frame (after removing the one fan) and scrubbed the case with a magic eraser which got much of the marks off. And let that and the logic board completely dry overnight.

I have a lot of time today to look at it, but I don't really know what to do. I have very few of the caps for the analog board on hand and don't want to risk destroying that board when I don't know if any of the caps are bad. I'll see I guess.