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gkmaia

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  1. WOW spot on! A block of the LS257 failed open, exactly where the bus signal was stuck high. Replaced it and booted just fine!
  2. Yes, that is weird. I removed U12F and 11F as I am getting D9 in the data bus stuck high when compared to a working board. As they were the buffers between processor and memory I thought they could be stuck open. But they are both fine. Also the ROM ICs use the data array but I tested them on another working board. Problem is this schematic is quite incomplete... the other weird thing is that Sim 1 bank A and sim 3 bank B use the same buffer. Same for sim 2 and 4. This means this type of fault should be on the sim card, not on the main board. So... confu
  3. I got this error 00000003 00040000 By looking at Troubleshooting_Your_Macintosh_1992 : The RAM test failed while testing bank B, after passing the chunk tested for code $0002. The Z field indicates which bits failed as in code $0002. Also the second line shows what bits may have failed. But not sure how read 00040000 and what clue it makes. I was initially running 4x256kb of RAM I am sure works. Also tried to eliminate bank B by switching the resistor from 35 to 36 and using 2x1MB. Still the same issue.
  4. I am really stuck with this one. I am 100% positive the 8DIP IC pointed with the red arrow is faulty. As I swap it from another working PSU gets the PSU going again. The Ic has only a "177" marking. I suspected it was an op amp but it was a guess. Not sure what this little board does. I tried the common single and dual channel op amps and also a OP177 a precision single channel op amp... no success. Anyone have any idea of what IC could this one be?
  5. Anyone out there with some experience with a SE psu? I suspect the ic in the photo is a 8dip optocoupler. one of my SE has it faulty. Would you guys know the specs for this ic?
  6. I've made a few plots from a working SE power supply while fixing another. As I could not find a decent schematics I am uploading what I did as it could be useful to other people.
  7. Cool, thanks. that makes sense. I've made a little clip on my 3 printer to hold them safe so that wont be a problem. One interesting thing is on the conners the platter does not fit perfectly to the motor spindle. It has a bit of play. And with that in mind I did an experiment by swapping 2 PCBs, each with it is own calibration, in the same platter assembly to check how the radial calibration would react. And they both run perfectly. That tells me either there is a cosmic coincidence these platters had the exact same physical alignment or the tolerances for radial align
  8. What is the reason why the heads should not touch each other?
  9. Changing the ID worked!!! Thanks! Transferred a bunch of data and the DIY cable did pretty good.
  10. Thanks for all the answers! I will change the IDs and see what happens.
  11. I got an LCII with a hard drive inside. As I wanted a second hard drive I decided to make an adaptor to connect my other SCSI drive to it's rear SCSI port. If I start with the external HD connected it boots from the external Hd and the internal is not visible. If I start with the internal HD and later connect the external HD the external does not mount. Anything I should do such as setting the external as slave? Or come pinout on my adapter that I am missing?
  12. Are onboard RAM words tested on Classic II P.O.S.T? If they are not is there a software that tests all onboard RAM words? Compatible with Mac OS7.
  13. I do not have any goo on the head bumpers. But lots of white goo at the seal edges. The plate filter was soaked in good as well. Is there any drawback in terms of alignment if I remove the plates? Would be good to take them out and clean the whole assembly and look under the plates. What would you use to clean a plate? IPA alchool?
  14. I think I got the answer for my question. But I guess will be valuable to share. I have two connor 40mb drives. One 34 pin from my portable. One 50 pin from my LC. I swapped the logic board between the portable 34 pin case and the LC 50pin case. Turns out that my 34pin logic board + my adapator + 50pin case works perfectly on my LC. Would you recommend opening the faulty case? is there anything that can be fixed in there? Or that is pretty much a lost cause?
  15. Have anyone ever successfully disassembled the Portable LCD display? I mean remove the panel from the PCB and contacts? If so, could you share your results?
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