Apple SC20 Problem

[Concorde1993]

Hello once again:

Amidst the degrading display problem I have been having with my SE, I can safely say that my 512ke/Plus hybrid is working perfectly, as if it were almost brand new. Nevertheless, there is a problem.

The fellow that I purchased the computer from finally found the external hard drive for it, and the ImageWriter II printer, which was combined as a package. Altogether, I spent about $40 on this unique system.

To get to the point, the Apple SC20 drive, which has OS 6.0.4 installed on it, and a host of other programs, such as Word, Excel, Adobe Illustrator 88, MacPaint, etc. boots the Plus (I get the glorious happy Mac/Welcome to Macintosh), however, when I get to loading the desktop, the Plus crashes (Sorry, a system error occurred, ID Number= 02).

I have tried the drive on my SE, and it works perfectly (I can access the data on the drive, etc.). However, I must restart the computer to run 6.0.4, as I have 7.1 on the SE, and as we all know, we cannot have two systems running simultaneously, unless we have a program like Switcher (I do, but the boot disk no longer works; I get an error -39 message when I try to open the program from the floppy).

There are moments where I can boot the Mac Plus from a boot disk, then have the SC drive appear on the desktop. But get this, when I open it, no icons appear (although it recognizes that software is on the hard disk; about 6 files, or so).

I have an interrupt switch on the Plus (a great feature by the way), but I have been unsuccessful in overriding the System bomb (I get a whole bunch of 0's appear on the dialog box).

Any help, of course, will be greatly appreciated.

 

[Mac128]

The drive is formatted differently for a Plus and an SE which have different interleave schemes. Which was this formatted for? I wouldn't expect these kinds of problems but anything is possible. There could also be extensions in the System folder incompatible with the Plus. Also, check the termination. The Plus has no internal Termination, but the SE does. So there could be a number of issues contributing to this problem.

 

[Concorde1993]

Hello Mac 128:

I managed to get the files on the SC20 to appear on the Plus. All I had to do was create a new 800k boot disk with the System folder installed on the SC20 drive. Now the Plus boots to 6.0.4 (on the floppy), and recognizes the files on the hard drive. However, I do not want to rely on floppies in order to boot the computer, hence why I got the SC20 drive. How do I instruct the Plus to boot from the hard drive, instead of the floppy (the hard drive will not properly mount without a floppy; I get a system bomb ID=02 when I do so)?

In regards to termination, I have a terminator plugged in to the back of the SC20. There are no problems with it.

 

[Mac128]

The most obvious step is to replace the system folder on the hard drive with the one off the floppy. If that still doesn't work then I would backup the HD and reformat it on the Plus ... Assuming you don't want to use it on the SE in the future - different interleave. Then re-install the system from your floppy and if it boots up correctly, re-install the content to the disk.

 

[MacJunky]

Assuming you don't want to use it on the SE in the future - different interleave.

The SE should be able to use the drive with an interleave ratio that accommodates the Plus, it will just be a bit slower(on the SE) than if using the best interleave ratio for the SE.

 

[Mac128]

The SE should be able to use the drive with an interleave ratio that accommodates the Plus, it will just be a bit slower(on the SE) than if using the best interleave ratio for the SE.

A bit slower!? That's relative. And on an SE, who wants it slower? I would format the drive for the Mac you're using it on. Definitely don't format it on the SE for use on the Plus as it will be really slow, and may be contributing to your startup problem.

 

[Concorde1993]

The most obvious step is to replace the system folder on the hard drive with the one off the floppy.

In regards to Mac 128's comment, the system folder I put on the floppy was the system folder originally installed on the hard drive. The information I put on the disk was the system file (of course), chooser, background, startup disk, and a couple of other things but it does not come to mind right now. For some reason, HD setup was not installed on the hard drive, so I could not include that with the new startup floppy.

To give some background information on the hard drive, the individual I bought it from originally used the drive as his startup disk for his 87 Mac SE, which had the dual 800k drive setup. The SC20 is even labeled "MAC SE." Furthermore, I read over the comments made about speed. Since I have tried the SC20 on both the 512ke/Plus hybrid, and the SE, there are no improvements in the amount of time it takes for the disk to mount. As a matter of fact, the drive is pretty quick in response (considering there are about 230 files on it). The only exception would have to be with the SE, since I have to boot it first in 7.1, then restart the computer to have it boot in 6.0.4 on the SC20 (but that does not bother me).

In regards to backup, I have version 1.1 of Retrospect (with its original box & manuals too!), and naturally I do intend to archive, and duplicate everything I have on the drive in case it happens to fail.

 

[Mac128]

the system folder I put on the floppy was the system folder originally installed on the hard drive.

Then that suggests to me the disk formatting interleave is the problem. The SCSI disk drivers were very finicky in those days. There's plenty of utility software developed after the SE which is not compatible with the Plus. And 230 files is nothing. Try writing large files to and from the disk and you'll notice a difference on the Plus. Obviously there IS a difference since you cannot boot from it on the Plus.

The only exception would have to be with the SE, since I have to boot it first in 7.1, then restart the computer to have it boot in 6.0.4 on the SC20 (but that does not bother me).

I don't really understand that one. Why do you have to boot into 7.1 on the SE? Just boot off the external drive directly by selecting it in the startup disk control pane (Also something the Plus can't do). Alternately you could get either System Picker or System Switcher which allow you to hold down a specific key combo during startup and chose which drive to startup from. Apple+shift+option+delete was the way to bypass the internal drive in later systems but no sure if that was supported in 7.1.

 

[Concorde1993]

Hello Mac 128:

Thanks for the reply.

In regards to 7.1, since my SE has an internal 40MB hard drive, when I boot it from a cold start, the internal hard drive immediately kicks in (although the SC20 is hooked up to the SE's SCSI port, and is switched on). Since the SC20 does not mount onto the hard drive (probably because of the system folder that has 6.0.4 installed, because all of my previous external SCSI drives- like my Jasmine Direct 80, which no longer works- were able to mount onto the desktop, but did not have a system folder installed, only programs), my only alternative is to reboot the SE. After that, the SE begins communicating with the SC20.

I have heard the horror stories about these drives randomly crashing, and so forth. I do have intentions of cleaning the innards (from the looks of the back of the cooling fan, its quite dusty), however I would require instructions as to how to effectively open the case without causing any cosmetic damage (I noticed there were no screws at the bottom, or on the sides).

BTW, it was not my intention to sound like I had God-knows-what amount of files. My external 500GB drive for my MBP has over 2 million files (most are Word & Podcast files) backed up on it, so naturally 230 would seem to be a fairly decent amount of files, especially for an almost 25-year-old Apple drive. Nevertheless, the programs that are on it are interesting, and worth keeping for my vintage 512ke/Plus hybrid.

 

[Concorde1993]

I forgot to add, I will attempt that keyboard feature you mentioned in your previous post, and see if it works on 7.1. Either way, I am more concerned about preserving the data on the SC20, and putting it towards some good use on my 512ke/Plus.

 

[JDW]

I do have intentions of cleaning the innards (from the looks of the back of the cooling fan, its quite dusty), however I would require instructions as to how to effectively open the case without causing any cosmetic damage (I noticed there were no screws at the bottom, or on the sides).

I was able to open my HD20SC housing after spending about 1.5 hours on it. I took so much time because I wasn't sure exactly where to apply pressure on the plastic tabs that hold it together. I should have taken photos of the process so others could do the job more easily. Sorry about that. But what I can say is that it can be done. As I recall, I had to use 2 flat-head screw drivers to slowly open the case, bit by bit.

Here are a couple photos of my HD20SC sitting beneath my SE/30:







And here is the SCSI hard drive mechanism I used to swap out the stock drive:

http://www.flickr.com/photos/66071596@N00/527548551/

Lastly, I would like to add that I put a resistor in line with the fan. That reduces it's speed and overall cooling, but once you peer inside the HD20SC housing, you will see that the drive will definitely be cool enough with a lower fan speed (and perhaps even no fan at all). I reduced the fan speed with the resistor in order to reduce the noise. In the stock condition, the fan is louder than even a loud hard drive!

 

[Mac128]

That reduces it's speed and overall cooling, but once you peer inside the HD20SC housing, you will see that the drive will definitely be cool enough with a lower fan speed (and perhaps even no fan at all). I reduced the fan speed with the resistor in order to reduce the noise. In the stock condition, the fan is louder than even a loud hard drive!

The fan is overkill because the drive case is designed to hold a full height 5.25 drive, which I think the largest of the SC offerings were.

 

[Concorde1993]

And here is the SCSI hard drive mechanism I used to swap out the stock drive:

In regards to JDW's comment, I have an 80 meg Quantum drive, which was probably designed for an SE/30, or a Classic II. I am not sure if it works, as I have not tested it out in a while (it was supposed to be a replacement for the internal 40 meg Lacie drive I have in my SE, but that never happened).

Although I would like to keep the SC20 with its stock 20-meg drive, can I potentially swap the 20-meg with the 80 (just to see if it works)?

Thanks again for the replies.

 

[JDW]

Yes, you can use any 50-pin drive, of any byte-size. You simply have to note that System 6.x can only see up to 2GB on hard drives. But since 80MB < 2GB you can certainly use your drive with any OS your Mac supports.

The only thing you have to watch is TERMINATION. You can often terminate newer SCSI drives using a jumper on the drive itself. Older drives don't offer that, so you will need to use an external SCSI terminator. If you don't terminate the drive, it won't work at all or won't work reliably. And this goes without saying but I'll say it anyway. If you terminate the drive using a jumper on the drive itself, you do not need any terminator on the external SCSI port of the HD20SC. Just terminate it once (either internally or externally).

 

[Mac128]

Just terminate it once (either internally or externally).

Is that that true even on the Plus which does not provide termination power?

 

[JDW]

To begin, this Apple Discussions thread talks about "double termination," which is what I was warning against:

http://discussions.apple.com/message.jspa?messageID=2748302

Obviously, if you put more than one device on the external SCSI connector of the PLUS, you will have to terminate the first and last device. But my previous post here was written under the assumption that the HD20SC would be the only external SCSI device attached, hence it needs only 1 instance of termination (either via jumper on the drive itself, or a terminator connector block externally attached to the HD20SC). This page shows a photo of the "Centronics" terminator connector that I've been talking about, which attaches externally to the HD20SC (and many other external SCSI hard drives):

http://www.jagshouse.com/plusharddrive.html

As to "termination power," you're right about the Plus NOT supplying it. However, most Apple SCSI drives provide it so they can work on the Plus:

http://lowendmac.com/tech/termination.shtml

With that said, I've not verified this myself because I don't have a Plus.

In the past, I always preferred to use Active Terminators because they supplied termination only when needed:

http://www.welovemacs.com/scs-term.html

It therefore would be good to test the following 3 conditions (all with the HD20SC being the only item in the external SCSI chain):

1) Jumper based termination on the drive mechanism itself (if the drive offers it).

2) A "passive" Centronics terminator externally placed on the HD20SC.

3) An "active" Centronics terminator externally placed ont he HD20SC.

 

[Concorde1993]

Hi JDW:

I've got an external terminator, which I place into the top SCSI port on the SC20 (I prefer using the bottom port to hookup to the Plus for some reason). I will take your advise on the other terminators you mentioned, of course.

I will see about transferring the 20 meg drive with the 80 when I have time, and I will let you know what comes of it.

Since you mentioned that the maximum memory for an external hard drive on a Mac running System 6 is 2GB, what is the maximum for 7.1? I tried hooking up my 9GB Avid external drive to my SE, but I got a sad Mac instead (that was probably the first time I ever saw a sad Mac appear on any classic mac; it looks so weird).

 

[JDW]

System 7 allows between 4GB and 2TB, depending on the version of 7 you use:

http://support.apple.com/kb/TA27115?viewlocale=en_US

 

[Concorde1993]

I opened up the SC20 last night, and cleaned the inside with a PC vacuum cleaner. It was not as dusty as I thought it would be, but it still required a cleaning.

I have intentions of replacing the original 20 meg drive with an 80 meg Quantum drive to see if the Quantum drive works, and to fix this startup error. I noticed that it is housing a 5.25" Seagate drive. How would I go about removing this drive, and properly housing the Quantum drive (since it is a standard 3" drive)?

I have provided pictures of the SC20 (after cleaning), and the Plus & SE.