I'm using a MacMini as my primary computer and you're right when you say that "obsolete" computers are still useful for many applications. The one reason I'd like to get my LC running again is the programs on it are mostly devoid of the bells & whistles in the latest versions of software (that I don't use or need).
Do you still have the external SCSI enclosure (with its own power supply)? Has the remaining hard drive been tested again, both installed internally and in the external box? No sound of a spinning disk?
It is strange. I guess that you have double-checked all cables etc. Yes, it may become necessary to test yet another hard drive, but before doing so you should really have a set of disk tools floppies with various utilities (such as Apple HD SC Setup 7.3.5, Lido 7.5.6 and Mt. Everything). It is not too difficult to adapt Network Access disks to hold the utilities in question, but you would need a working older Mac with a hard drive to do so. Perhaps it is time to look for something like a PowerBook 520/520c/540/540c (which has built-in Ethernet) to be used for floppy modifications and as an intermediary.
If you can find someone with a suitable older (approx. 1991 to 1997) Macintosh computer, here is a list of older Apple software:
A plain Network Access Disk 7.5 can be used as a general startup disk (and, as mentioned earlier, it can be the base for utility disk modifications). It can also be used to access files on another Mac via a simple LocalTalk network (a normal MiniDIN-8M to MiniDIN-8M printer cable between the serial printer ports):
Disk Copy 4.2 (the Make A Copy button) can be used to create a properly sector-copied floppy from a downloaded NAD 7.5 disk image:
Apple HD SC Setup 7.3.5 can be found here:
For information about other programs, you may want to try an Internet search for something like 'format SCSI Mac'.
Please note the volume size limits:
Mt. Everything can be used to detect a drive on the SCSI bus:
SCSI Probe was a similar utility:
BTW, with an appropriate cable/adapter, many PowerBook computers can act as an external hard drive in SCSI disk mode (see, for example, page 31 in the PB 500 series manual below).
Thanks for the links but I don't have much hope of finding any older Mac computers or software (I've looked!). Today I hooked up the APS external drive and tried both of my HDs in it. They both powered up and spun! but the 'new' logic board couldn't find either of them. When I plugged one of the HDs directly back into the computer it would not power up & spin and no SCSI drive could be found:-(
In addition, I don't get a start up chime unless one of the HDs is plugged into the logic board. All that's left is the power supply but all the voltages are correct. This is getting old and I could scream!
I appreciate all your help but I think it's time to move on.
>but the 'new' logic board couldn't find either of them.
The first requirement for a hard disk to become visible on the Desktop is of course that it has been properly formatted/initialised (with an appropriate driver installed). The second would be that the SCSI bus/chain is OK. Otherwise, the hard disk will not mount.
When you say that no SCSI drive could be found, was that a result of a drive search in an old HD SC Setup program on a Disk Tools floppy? HD SC Setup may have difficulties detecting drives; third-party drives (or Apple drives with an altered formatting) cannot be expected to appear at all. It is really essential to have access to alternative tools.
Is there an Apple User Group in your area? If so, someone there could perhaps help you locate a suitable older Macintosh computer.
A problem with the power supply under specific load conditions cannot be ruled out, but it all seems to work well with the floppy drive.
If necessary, do not hesitate to post back later with questions about floppy modifications etc.
I wish you a Merry Christmas!
I hope that your Christmas was happy and joyful.
It was good to get away from the Mac LC problems for a day or two but I did have one thought. When power is first applied to the computer at start up, should the internal HD begin to spin even before the boot sequence has gotten very far? The reason I ask is because when either drive is installed in the external APS box, the drive starts to spin as soon as the box is turned on (without being connected to the LC). Either HD has an OS installed and worked fine in the LC for years. As I said earlier, the voltages at the PS connector and the HD connector are ± 0. 2 volts but the PS is the only thing I haven't dug into.
>When power is first applied to the computer at start up, should the internal HD begin to spin even before the boot sequence has gotten very far?
I tested this with my LC III (which has a Conner 30080E hard drive). Nothing was connected to the (external) SCSI port. To be able to hear the hard drive better, the fan was temporarily disconnected. Immediately after the computer was turned on, the hard drive started spinning. Shortly thereafter, the startup sound could be heard. Then the arrow appeared. After that a Happy Mac followed by the Welcome to Macintosh message, and the normal Desktop.
Another test with the SCSI (hard drive) cable disconnected at the board had the same result (the hard drive spinning up and then the startup sound). Then the arrow. Finally, a floppy icon with a flashing question-mark was shown on the screen. No Happy Mac etc. Upon insertion of a Network Access floppy, the Happy Mac appeared, followed by Welcome to Macintosh, and eventually the normal Desktop.
Happy New Year. Good news for 2014!
As a last resort I opened the power supply of my LC and found at least two badly leaking caps which I replaced with used caps from my junk box. However, the result was not good; only one of the 5V supplies was putting out the correct voltage. Ordered an assortment of new caps from China and another TDK LC PS from eBay. I now have a working LC computer, the original TDK PS to repair, and the original logic board that has new caps and works fine with the new PS but has no sound. Both HDs are working fine and all apps and files are intact.
The key was your observations that the HD spun up as soon as the computer was turned on. I didn’t recall what the sequence was but the clue for me was the fact that both HDs ran when put in the APS external drive box and didn’t run at all in the LC.
It has been a fruitful and at times frustrating experience. One might question the logic of spending time and money on a 22 year old computer, but I considered it a challenge and worth the effort.
A final question; do you know of a source for a schematic or a functional layout of the LC? Or do you know which specific device(s) are used for sound? I’d like to get my original logic board back to fully operating condition.
Lastly, I’d like to thank you for your help, expertise and quick responses during the past few weeks. Thank you.
Thank you. I wish you a Happy New Year, too!
As far as I know, Apple never published schematic diagrams for any product. However, they did publish block diagrams for various computer models in their Developer Note series. Earlier, you could download these hardware documents from Apple's developer site, but this does not appear to be true any more (a web search could possibly provide some results, though).
As far as the sound is concerned, did you check whether a switch in the speaker/headphone jack properly closes the circuit to the internal speaker when nothing is connected externally? If necessary, a small amount of a good contact cleaner may help.
Glad to hear that you solved all the other problems.
Not sure if this is directly related - but the Inside Macintosh had some very techical details to the hardware and software. There was some basic schematics when I read through them. The books were sold to developers back in the day, and you can get them at a yard sale price on Amazon (which I got the first 4 volumes in the last year or so.)
>Apple never published schematic diagrams for any product.
Just to clarify, I was referring to 'component level circuit diagrams' in this very case.
Earlier, developer notes (which often contained block diagrams) for old hardware products could be found here:
Unfortunately, that address now returns an error message. However, one should perhaps not rule out that the page exists in an Internet archive somewhere. Generally speaking, it has become increasingly difficult to locate older Knowledge Base articles, etc. Sometimes the material is still available at an Apple web site, but you may have to use Google to find it.