68kMLA Classic Interface

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Classic II – won't start after cleaning
Posted by: blindowl on 2023-01-20 21:39:27 On early Macs ROM chips could cause vertical stripe problem, clean and reseat ROMs!. I'd also be suspicious of the onboard RAM chip. Yeah, already tried that, unfortunately. 🙁 Chips are very clean and seated properly.
Posted by: nukem on 2023-02-23 09:55:17 Make sure you have a battery. The reset line will stay low if there is no battery.
Posted by: 3lectr1cPPC on 2023-02-23 10:11:22 Huh? The classic II doesn’t need a battery to start. That’s systems like the Mac II big box series and the 475 series macs
Posted by: joshc on 2023-02-23 10:50:08 I've also had garbled screen caused by Egret problems. Make sure you have a battery. The reset line will stay low if there is no battery. This is not true. A Classic II does not need a battery to start.
Posted by: mg.man on 2023-02-23 12:56:35 FWIW, it will also boot up (no drives attached) with no capacitors. 😀
Posted by: mg.man on 2023-02-23 12:57:23 Without the surface mount electrolytic "cans" that is...
Posted by: blindowl on 2023-02-24 03:01:43 Since my last post I've put this project aside for the moment. Summery of what I've done: • Replaced all caps on the logic board • Adjusted the voltage rails on the analog board • Changed to another pair of RAM modules — computer now actually started to boot normally, but with intermittent issues. I SHOULD’VE STOPPED HERE! • Soaked the logic board in vinegar and rinsed with water — BAD IDEA! Now it didn’t start at all... (the start of this thread). • Soaked the logic board in vinegar again, rinsed with IPA. • Replaced a missing/damaged micro cap on the back of the logic board • Removed and cleaned the Egret chip — computer started again! PHEEEW • Replaced several caps on the analog board • Re-adjusted the voltage rails • Replaced the onboard RAM chips — twice! • Replaced all capacitors (except 2 × 1 uF) on the logic board — again! Better soldering job this time Issue is virtually the same. Just another pattern on the screen (after the swapped RAM chips I guess). Pattern is less garbled, though. One day I will remove and clean the Egret chip again. Then I'm out of ideas. I've beeped the most obvious components and traces with the multimeter, and everything has been normal.
Posted by: chrisrueckert on 2023-12-08 12:00:26 Did you ever retry to fix the Classic II? I'm curious to know as I have a similar issue with mine.
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