Tough SCSI problem

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Joined: Dec 8 2009
Posts: 5

Hello everybody,

I'm new to the forum; thanks for having me.

I'm a big fan of the CC and I use a CC I bought at a store myself in 1993. I turn it on everyday and use Word for text processing (I write SF). I've been playing and fixing macs for over 20 years but this is a hard nut to crack.

A few days ago I turned the CC on but it wouldn't boot. It gave me the disk with the question mark. Disk gone? Just like that? Strange, I thought. Booting up from an external device (ZIP drive or the MO disk worked fine, as well as with the floppy disk). The disk is an IBM OEM made for Apple model WDS-L80, 80 MB. Norton Disk Doctor could not examine the disk, nor HD Setup, nor HDT tool. No tool could work on the disk.
SCSI ID is zero, so SCSI probe or SCSITOOL found the disk and gave a correct description. But that was as far as they could go. I even tried a mkfs tool from NETBSD which returned a SCSI error #5, the same one returned by NDD.

I formatted an identical drive (I have a spare one), connected it to an external case and it mounted on the desktop (as far as I can tell the external devices have been working fine). I installed the good disk in the CC and to my surprise (it is not configured to SCSI 0 though, it had ID4) it behaved exactly as the other one, SCSI error #5! SCSI Probe show ID4, but no tool can work on the disk.

Questions:

1. The SCSI controller is one for the entire chain. Could it be bad only for the internal HDD?
2. Does the SCSI ID of the internal HDD HAVE to be zero? Right now it is 4.
3. The cable could be bad? Hard to think how it became bad from one day to the next. It is an internal cable. As I described above, nothing changed from one day to the next.

Some extra info:

I have checked and changed all the capacitors on the logic board after the problem started. The problem persisted.
The terminator is ON in the last device of the SCSI chain: the ZIP drive. CC(ID7) -- HDD(ID4) -- MO(ID3) -- CD300(ID5) -- ZIP(ID6)Terminated. The problem is the same with the external chain connected or not.
The specs for the disk can be found at http://www.bk0010.narod.ru/DRIVESPECS/IBM/1734.txt although it is not completely accurate. I think the Apple OEM model is slightly different. The SCSI Jumpers Information is right-to-left inverted. PIN 1 is the first one on the right, not on the left as it is shown at the link.

I have another CC logic board at my parent's I could swap and see if it works, but it is a loooooong drive.

I'm trying to find if anybody has seen something similiar before and could give more ideas.

Any help is greatly appreciated.

Long live the Colour Classic!!

Cheers,

Marcio

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gsmcten's picture
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Joined: Oct 4 2005
Posts: 2626
Re: Tough SCSI problem

mpocciot,

Welcome!

Steven Smile

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Steven (gsmcten)

"Apple ][.....It's ALIVE!!!!!"

speedyG's picture
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Joined: Nov 16 2011
Posts: 2413
Re: Tough SCSI problem

Hello Marcio,
welcome,
allthough i´m only using Apple II series devices there might be a possibility that
the internal part of the chain demands the internal units to have either ID = 0 or ID = 1......
i´d give it a chance.... maybe there is a kind of hardware coding at the internal plug
that kind that higher 3 bits have not been routed to the internal connector...
sincerely speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....

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Joined: Dec 8 2009
Posts: 5
Re: Tough SCSI problem

Hello Steven,

Thanks a lot for the warm welcome. Always good to make new Macintosh friends.

Cheers,

Marcio

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Joined: Dec 8 2009
Posts: 5
Re: Tough SCSI problem

Hello speedyG,

Thanks for your comments.

Yesterday I tried another logic board without touching anything else; just swapped the original with another one from a "working" CC. It booted from the Magneto Optical external disk and the IBM HDD mounted on the desktop!

I changed the startup disk to the internal drive, SCSI ID 4, and rebooted. It worked! So I guess the internal drive doesn't need a SCSI ID of zero after all.

Then, for the final test: swapping the Logic Board again. I removed the LB and inserted the original one: the disk is gone. Back to the same problem. I guess the problem is in the original LB.

Now, I need to find out in which portion of the LB the SCSI controller is. If there is a component I can replace, maybe I can make it work again. But, it may be beyond repair without proper tools or a lab. If it is a problem in a CHIP (maybe a static discharge caused damage) then it will be too hard to resolve. What is keeping me awake at night is the fact that all the external devices of the chain are working fine and, as far as I know, it is the same controller for all of them. Any ideas?

In all these years collecting old macs I have found out that fixing them is as exciting as using them Smile

Have a great day.

Marcio

speedyG's picture
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Joined: Nov 16 2011
Posts: 2413
Re: Tough SCSI problem

Hello Marcio,

well the results are interesting....

anyhow at this point some Mac User should better take the torch and march ahead...
my knowledge is restricted to the SCSI chip and it´s use and spec´s

at this point it´s getting CC specific and i don´t have any circuitplans to check or own
experience to that system.... In most cases in that days SCSI was realized by use of a 5380 chip from NCR.
If you have a circuitplan it would be usefull to view any kind of logic between that chip and the connector.
There might be some kind of latch or other logic used there which micht have been damaged....

But here are several quite experienced Mac Users present that might
help you ahead... not to forget to mention that there are 2 or 3 specific sites
focused specially to the MAC...

wish you good progress
sincerely speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....

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Joined: Dec 8 2009
Posts: 5
Re: Tough SCSI problem

Hello speedyG,

Thanks again for the information. I'll have to check and find out about the chip on the LB, maybe it is the same 5380 chip.

Thanks for your help.

Regards,

Marcio

Offline
Joined: Jun 18 2010
Posts: 107
Re: Tough SCSI problem

If there was a leaky cap, it may have eroded one or more traces to the SCSI chip. You might want to get a schematic and try checking continuity from the chip to the SCSI connectors.

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Joined: Dec 8 2009
Posts: 5
Re: Tough SCSI problem

Hello Jeff,

that's a good idea. I'll check that next.

Cheers,

Marcio