68kMLA Classic Interface
This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.
| Click here to select a new forum. | | A Classic, classic of classics story | Posted by: sircabulon on 2026-09-27 08:50:49
I finally got to go to VCF this year and my hyper-focus (aka obsession) went into overdrive and I have now found way too many compact macs. Prior the festival, I scored a two for one deal. It came with a non working Macintosh Classic and a non working Macintosh SE/30 priced together for $100. I jumped at the chance and picked them both up. The person I bough them from had another Mac Classic that worked with printer and everything that he was very proud of. He didn't know battery bombing was a thing and told me he got them for free years ago when a neighbor was trying to clean his house out. I told him about the issue and offered to open them up and show him. The two I had bought both had batteries, but they hadn't exploded yet. His remaining classic however, it spewed acid everywhere.
He gave me a deal, so I offered to recap the classic board I just bought and give it to him for free. That turned into an entire wild goose chase. I could not get it to recognize more than 2MB of RAM no matter what, and the sound I could not get to work. I have another Classic that works perfectly, and figured out that the analog board was to blame for the sound, and the board for the Classic I just bought has other issues. It was missing the UH6 74LS174 chip when I got it, so sometime in the last 35 years, someone messed with it.
This lead me to getting another 2 for 1 deal. This one came with a Classic and a Plus for $80. Recapping the Classic fixed the boot issue, it sees all the RAM, but it also has no sound. After recapping the Analog board, no sound again. I adjusted the voltages, got them really close - still no sound. This started to piss me off, so I decided to step back and think of what the simplest problem could be. On the two that don't work, the speaker resistance is showing 16Mega Ohms and 23 Mega Ohms.
I put my oscilloscope lead on the positive speaker wire and saw that it was moving during startup. I have a spare IIcx speaker, and I know the resistance is different, but I went ahead and put jumpers on it and attached it to the analog board at boot. The sound was working.
I have a Classic II with no sound as well. Depending on what I find there, I may have to say these speakers just suck and will fail. My pluses, SE's Color Classics, and every other compact Mac I have seen never had the speaker fail. These are all coming from different people, and I am storing them well. I am starting to wonder if different versions of the analog board start to overdrive the speakers when they caps start to fail, but I am not sure how to prove that out. I haven't recapped the analog board on the Classic II yet.
Also, one of the classics now has the screen rotated by like 3 degrees and I can't find a way to adjust it. Any help there would be appreciated. | Posted by: bibilit on 2026-09-28 07:14:57
Also, one of the classics now has the screen rotated by like 3 degrees and I can't find a way to adjust it. Any help there would be appreciated. On the screen neck, you have got the yoke (the winding) hold by a band with a tightening screw.
unscrew it, and then rotate the yoke the way you want to get it to the right position.
To be on the safe side, first rotate the yoke when the Classic is unpluged, the yoke is tight and will need a bit of force to spin.
Then plug it back, switch it on and use a wooden stick to rotate the yoke until the image is fine, tighten the screw back when finished. | Posted by: lauland1 on 2026-09-28 07:53:00
I've seen a lot of classic and classic 2's where random soldier joints on the analog board will start to fail, so be sure to look at those, if you haven't already.
As far as I can tell, the analog portion of classics and classic 2's is "mostly the same" and can be safely swapped, which helps with testing.
Speaker problems are odd. If voltages were enough to do that due to failing caps, then other voltages wouldn't been bad too and could've damaged other things. Anything that'd kill a speaker is borderline dangerous. | Posted by: sircabulon on 2026-09-28 11:16:54
On the screen neck, you have got the yoke (the winding) hold by a band with a tightening screw.
unscrew it, and then rotate the yoke the way you want to get it to the right position.
To be on the safe side, first rotate the yoke when the Classic is unpluged, the yoke is tight and will need a bit of force to spin.
Then plug it back, switch it on and use a wooden stick to rotate the yoke until the image is fine, tighten the screw back when finished. this makes a lot of sense! Thank you! | Posted by: sircabulon on 2026-09-28 11:18:57
I've seen a lot of classic and classic 2's where random soldier joints on the analog board will start to fail, so be sure to look at those, if you haven't already.
As far as I can tell, the analog portion of classics and classic 2's is "mostly the same" and can be safely swapped, which helps with testing.
Speaker problems are odd. If voltages were enough to do that due to failing caps, then other voltages wouldn't been bad too and could've damaged other things. Anything that'd kill a speaker is borderline dangerous. I need to rip the Classic II open again and do more testing. I will likely re-flow every joint based on my reading when I replace the Caps. I only tested the speakers on the two Classics. I am going to solder in an 8 Ohm speaker with a 47 Ohm resistor and see if the sound comes back reliably. | Posted by: DJ68K on 2026-09-30 03:50:26
When you're reflowing solder joints on the analog boards, give the boards a good inspection beforehand and see if you can spot any broken solder joints that will lead to an intermittent connection. These are only a few of the many instances I've found in my refurbishment adventures. The four-pin yolk connector, the 14-pin analog-to-logic board connector, the flyback transformer, and the big transformer are all solder joints I scrutinize and usually suck out all the old solder and replace with new solder, even if I don't see a problem. Once I had a 512K Mac spark and sizzle when I plugged it in: turns out the AC power connector had a cracked solder joint! Reflowed and it worked mint afterwards. If you see something crispy like 7781, don't be afraid to run a wire to reinforce the slightly toasted copper. If a pad lifts off the board but remains connected to the trace, run a bodge wire: bending that razor thin copper isn't something it's designed to withstand. On analog boards and power supplies, there's plenty of room so don't be afraid to use a big wire, like 24awg. It's probably carrying current, so it pays to oversize.
I picked up a Classic II from the same VCFMW a couple weekends ago and I've been mightily struggling with the logic board. I may make a thread here about my exploits; it's been a strange, frustrating trip through theory-of-operation troubleshooting land with an AI "assistant," checking for clocks and reset, hunting shorts to ground that disappear, and lifting individual pins on the 68030 to isolate things. Its analog board and CRT are in pristine shape, so I may just turn it into a parts box for a few other unfinished projects I have.
Finally, regarding the speakers: I've never had a Mac Classic-style computer's speaker fail on me, and I'm approaching two dozen in my (admittedly) oversized collection. I'd be very curious to know whether your speakers are truly failed or if it's a problem on the notorious analog board. | Posted by: sircabulon on 2026-10-08 05:53:47
The speaker one of the classics was absolutely bad. I put a new one in, and presto - I have sound. I think there may still be some solder issues though because the screen is being all jittery which makes me think there is a bad connection. I found some of the adjustments on the CRT, but I want to do a little more reading because I was not able to rotate the yoke after loosening and I don't want to break anything. | Posted by: sircabulon on 2026-10-08 10:20:19
I did find some cracked solder joints and re-flowed everything. A couple of findings:
- I mixed up my analog boards and this one needs a recap.
- There are two screws on the neck of the CRT
- The 8 ohm Mac Effects speaker works, but is way too loud and probably over-driving the circuit.
- The 8 ohm speaker with a 47 ohm resistor is perfect | | 1 |
|