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WOW spot on! A block of the LS257 failed open, exactly where the bus signal was stuck high. Replaced it and booted just fine!

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...

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...

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...

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?

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.

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...

What is the reason why the heads should not touch each other?

Changing the ID worked!!! Thanks! Transferred a bunch of data and the DIY cable did pretty good.

Thanks for all the answers! I will change the IDs and see what happens.

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...

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.

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...

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...

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?

That is such a valuable post. I am trying to restore my Portable and my hard drive stoped working, maybe you guys can give me some light.  All started when I tried to format the drive to install a clean system. While running the HD SC Setup I did clean the partitions, create new ones and when I...

Yes, you are right. But was also good to get to know the board better. Really did not need to do that but I find fun putting a board apart like that. In the end was the TDA4605.

I am going over a classic II board and my one has this blue bodge wire. Looking at some photos at the web I see quite a few boards with similar bodge.  Do anyone know what is the purpose of that? Is it a factory fix or DIY upgrades? Looking at bomarc's schematics I see the connection.  Can...

I have a few of these HD drives out of SEs, Classics, LCs... and they all seem to be perfect in terms of logic.  I've attached some scans I did on a good working MFD 75W 01G and that may be useful to other people trying to pin point issues with this drive. From what I can see all my non...

I got a fried resistor on my classic. I imagine that is a thermistor but not sure. From the schematics I would say it is a 20ohm at room temperature. But unsure of the watts. Can any one give me a light on that one. Another question. If I replace the resistor with an ordinary 5w 5ohm resistor...