DistantStar001 Posted May 18, 2018 Share Posted May 18, 2018 I recently acquired two Apple Disk II drives for my Apple //e. I was able to determine that both drives work, except one (now drive 2) has a bad analog board (I swapped the boards to make that diagnosis). When I examined the defective board, I noticed that a chip (74LS125) had a big chunk of it missing. I've replaced the chip, but there's been no improvement. I was told that the kind of damage the chip suffered could have been caused by a short, but I couldn't find any. All the capacitors seem good, and I can't find any broken traces. I'm kind of at a loss now. I mean one drive is better than no drive, but I'd like to get both working if I can. Maybe someone can spot something I missed. (The first photo pre-repair. Quote Link to comment Share on other sites More sharing options...
trash_44fr Posted May 20, 2018 Share Posted May 20, 2018 (edited) Hello, In fact, the LS125 will blow up if it takes 12 Volts instead of 5 which happens when the 20 pin connector is not correctly plugged in the Disk II controller card (ie shifted by one pin). Since you have one working card, I suggest you tried every single IC of the defective one on it. There is good chance you'll spot more damaged ICs. Cheers, Edited May 20, 2018 by trash_44fr 2 Quote Link to comment Share on other sites More sharing options...
Keatah Posted May 20, 2018 Share Posted May 20, 2018 Ensure all your connectors and contacts are clean. Quote Link to comment Share on other sites More sharing options...
DistantStar001 Posted May 20, 2018 Author Share Posted May 20, 2018 Good to know, I've actually done that before. Quote Link to comment Share on other sites More sharing options...
DistantStar001 Posted May 21, 2018 Author Share Posted May 21, 2018 Hello, In fact, the LS125 will blow up if it takes 12 Volts instead of 5 which happens when the 20 pin connector is not correctly plugged in the Disk II controller card (ie shifted by one pin). Since you have one working card, I suggest you tried every single IC of the defective one on it. There is good chance you'll spot more damaged ICs. Cheers, Thank You Space Invader! I was able to narrow it down to the chip marked MC3470P Motorola 8045. Can you believe that someone actually threw these things away for what's likely to be less than $4 in repairs. Whoever it was kept the Apple II, but couldn't be bothered to fix the drives!?! I don't get it :-\ 1 Quote Link to comment Share on other sites More sharing options...
Osgeld Posted May 21, 2018 Share Posted May 21, 2018 I get atari consoles all the time "broken" that just requires jiggling the power switch ... if people are not going to wiggle a switch they sure are not going to sit down and trace a circuit fault Quote Link to comment Share on other sites More sharing options...
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