pbMacGeek17
Member
I've had a Macintosh LC 575 for about a year that has always worked pretty well. However, after being on the shelf for about the last three months, I could no longer boot it up. Everything looked fine until the Welcome to Macintosh screen came up. At that point, the system simply froze. I found I could boot from a floppy just fine and access the hard drive, but I still couldn't boot from it. I ran Disk First Aid and it found no significant problems. I then tried to run Norton Utilities, but it complained about memory and quit (the System 7 boot disk can only access 8 MB of memory which apparently, and surprisingly wasn't enough). At that point I assumed that the hard drive had gone bad so I went onto EBay and ordered a replacement (fortunately they are not that expensive anymore).
While I waited for the drive to come in, however, I became concerned that I might have been too hasty and misdiagnosed the problem. I decided to create a system folder on a Zip 100 and try booting from it. My first attempt consisted of booting from the floppy and copying the hard drive's system folder to the Zip. The copy operation was successful, so i set the Startup Disk to the Zip and rebooted. Surprisingly, I encountered the same problem: system freeze at the Welcome to Macintosh screen. I then booted from the floppy and installed a fresh System 7.5.3 on the Zip from CD and repeated the boot attempt only to run into the same result. I was now a bit concerned that the problem was in the SCSI controller and not the hard drive. First suspect was bad capacitors given the age of the machine. I pulled the logic board and looked closely for leakage; none was evident. However, since I had a spare set of capacitors from a previous SE/30 recap I went ahead and replaced all the 47 microfarad caps. God news is that the cap job went very smoothly; all pads were in excellent shape and it was easy to resolder the tantalum caps in place. Bad news was that the problem was exactly the same.
Still not willing to wait for the hard drive, I searched the web for anyone reporting a similar problem, but could find nothing of the sort relating to the LC 575. I did find a useful reference to a software diagnostic package called TechTool which I subsequently downloaded, installed and ran. I really like the tool since it does the most thorough test of hardware of any tool I've ever seen, but it didn't find any problems. I had pretty much resigned myself to wait for delivery of the hard drive, but did yet another online search. This time I fortuitously left out the 575 from the description of the problem and found a post on the 68K MLA site describing very similar problmes on an SE/30. The ultimate solution for that system was a new hard drive. I've not yet received mine, but am now more confident than ever that it will be the solution for my problem as well. I'll post an update once I receive the drive. My main reason for the post at this point is not to solicit help (though that may yet be coming!), but rather to put the information out there for others in the hope that it will reduce their repair time.
While I waited for the drive to come in, however, I became concerned that I might have been too hasty and misdiagnosed the problem. I decided to create a system folder on a Zip 100 and try booting from it. My first attempt consisted of booting from the floppy and copying the hard drive's system folder to the Zip. The copy operation was successful, so i set the Startup Disk to the Zip and rebooted. Surprisingly, I encountered the same problem: system freeze at the Welcome to Macintosh screen. I then booted from the floppy and installed a fresh System 7.5.3 on the Zip from CD and repeated the boot attempt only to run into the same result. I was now a bit concerned that the problem was in the SCSI controller and not the hard drive. First suspect was bad capacitors given the age of the machine. I pulled the logic board and looked closely for leakage; none was evident. However, since I had a spare set of capacitors from a previous SE/30 recap I went ahead and replaced all the 47 microfarad caps. God news is that the cap job went very smoothly; all pads were in excellent shape and it was easy to resolder the tantalum caps in place. Bad news was that the problem was exactly the same.
Still not willing to wait for the hard drive, I searched the web for anyone reporting a similar problem, but could find nothing of the sort relating to the LC 575. I did find a useful reference to a software diagnostic package called TechTool which I subsequently downloaded, installed and ran. I really like the tool since it does the most thorough test of hardware of any tool I've ever seen, but it didn't find any problems. I had pretty much resigned myself to wait for delivery of the hard drive, but did yet another online search. This time I fortuitously left out the 575 from the description of the problem and found a post on the 68K MLA site describing very similar problmes on an SE/30. The ultimate solution for that system was a new hard drive. I've not yet received mine, but am now more confident than ever that it will be the solution for my problem as well. I'll post an update once I receive the drive. My main reason for the post at this point is not to solicit help (though that may yet be coming!), but rather to put the information out there for others in the hope that it will reduce their repair time.
The Ethernet card looks almost brand new, so I don't think it's the problem. However, those two caps that I didn't replace pn the logic board are located right at the end of the PDS slot. Seems a fair likelihood that they're on the same circuit as the PDS slot and may be the cuplrit. Anyone know what size they are? They're labeled 100 6V so I'm guessing they're 100 microfarad caps rated at 6 volts. I really don't have the right tool to test them even after I've pulled them so the plan is simply to replace them once I verify their capacitance.
