Q: My Macintosh Classic shows blinking question mark :(

The tests that you have done do seem to cover all possibilities. The machine will boot from ROM, with the hard disk visible, which ought to rule out at least the most obvious hardware faults. Also, the hard drive itself and the operating system appear to be OK. A PRAM reset does not change anything.

Do you have access to a bootable disk tools floppy with Disk First Aid and Apple HD SC Setup? If so, you could begin by checking whether the hard disk shows up in Disk First Aid (if yes, verify, and repair if needed). You may then want to run Apple HD SC Setup and update the hard disk drive driver.

It is of course thinkable that some kind of borderline situation exists, where an electronic component is about to fail. A close examination (with a magnifying glass) of the board(s) should reveal leaking/bulging/discoloured electrolytic capacitors et cetera. At the same time, it may be a good idea to check the voltage of the (3.6 V) battery.  A warning: All work inside a compact Macintosh computer can be very dangerous because of high voltages in certain areas (even when the computer has been switched off and disconnected from the mains), and must be carried out by someone with the necessary expertise.

Jan

Hi,

Just guessing now. It may have something to do with (unstable) DC voltages. One can measure the 5 V and 12 V levels at the floppy drive port. Readings under different load situations (startup, floppy drive active, etc) would be of interest. Also, one should perhaps not rule out electrolytic capacitor issues yet (there are capacitors on the analogue board as well). Low (or no) logic board battery voltage may cause unexpected behaviour in some computers.

Jan

The blinking question mark means the Mac can't find the boot drive. More specifically, the boot loader. Go to System Prefs. and specify the boot drive. Then try to boot from it. On newer machines, holding the Shift key during boot rebuilds the boot loader. Try that and then try a normal boot. If still no good, back up your important files, erase the HDD and reinstall the OS. It should work after that.

Have you tried deleting the OS, and re-installing it? If not follow these steps:

Reboot your computer while holding the option key.

Load the Recovery disc

Choose disc Utility

Format Macintosh HD (Make sure you format Macintosh HD, not the one named after your actual drive)

Go back

Press install OSX

Never mind, you said you dud this already. Maybe it's time for an upgrade.

Hello again,

The voltages appear to be relatively well within limits (perhaps a bit low, but that may be related to voltage drops when measuring at the floppy port). No difference between readings at startup, during normal operation and when the floppy drive is active?

You mentioned that you had tested two hard drives. Was each drive installed internally? Have you at some point (with and without a hard drive internally) tested a hard drive in an external (powered) enclosure connected to the SCSI port of the Macintosh Classic? Any change if another device is connected to the external SCSI chain?

support.apple.com/kb/TA27743

Jan

you need to get a boot disc and the save it to the hard drive using disc utility's then it should save it then you should be good.

Not sure if this helps...

but did anything get tinkered in the System Folder? 98% of the chances of a Mac booting off a hard drive giving you a blinking question mark is because someone did something in the System Folder. Maybe the Mac isn't booting up because it's missing an extension or some other dependency of the System Folder? Not sure if old school SCSIs had the switches like the ATA and SATAs have today, maybe its on the wrong position, if there is such a thing?

I can't get why the PRAM battery would stop it from booting up, to me your hardware seems to be OK. I'm betting it's a software issue.