Apple /// Computer repair

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Last seen: 7 months 2 weeks ago
Joined: Nov 17 2019 - 18:34
Posts: 1
Apple /// Computer repair
So I recently came into posession of an Apple /// computer and have been trying to restore it--the power supply had broken but that was repaired, now when booting it up I get a jumbled mess of pixels. I did attempt to reseat as many of the chips as I could but I couldent quite figure out how to remove the  riser board to check the ones under it. However if anyone happens to have any idea as to point me in the right direction it'd be greatly appreciated.
Last seen: 20 hours 3 min ago
Joined: Nov 7 2019 - 13:49
Posts: 43
Service Manual
I just resurrected a broken, "brain-dead" Apple ///. The Apple /// Service Manual is really good. There's a fault tree of signals to check which you can follow step by step and guides you to the defect. You'll need an oscilloscope though - or some kind of instrument to tell if a signal is constant/stuck or alive and changing. It starts with the CPU reset signal and continues with the data/address lines - so you can tell if the CPU is alive at all. There is also section describing a "shotgun approach" - listing the most likely defect chips for certain symptoms. Do you see any kind of disk drive activity? If so, then it's likely a video-only issue only. Otherwise, when there is no disk drive activity, then it's a more basic issue affecting memory and or the core CPU logic - and your system is having a "no boot" symptom. The memory board is simply removed by pulling it. Be careful though not to bend the pins. Best is to lift it step by step at both connectors. cheers, T.
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