len-35
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Q: SCSI ID connections in APS case to the HD

I now have a revitalized LC with one exception. Does anyone have an old Apple hard drive mounted in an APS "Closed Face ZFP Drive"? Mine was working fine before my LC quit working. In the process of troubleshooting, I pulled the HD from the APS case without noting where the SCSI APS connectors go on the HD; dumb! If somebody can help with the correct data it would be appreciated!

Len-35

iOS 6.0.2

Posted on Jan 16, 2014 5:08 PM

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len-35

Q: SCSI ID connections in APS case to the HD

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  • by Jan Hedlund,

    Jan Hedlund Jan Hedlund Jan 17, 2014 11:21 AM in response to len-35
    Level 6 (9,901 points)
    Jan 17, 2014 11:21 AM in response to len-35

    Hello Len,

     

    Sorry, cannot help you directly, but I was wondering whether the sections about SCSI ID in the following articles/pages possibly could be of some interest in this case.

     

    http://support.apple.com/kb/ta27743

     

    http://www.ccadams.org/se/hard_disk.html

     

    http://www.obsolyte.com/faq/

     

    Jan

  • by Jan Hedlund,Helpful

    Jan Hedlund Jan Hedlund Jan 17, 2014 12:07 PM in response to Jan Hedlund
    Level 6 (9,901 points)
    Jan 17, 2014 12:07 PM in response to Jan Hedlund

    Addendum

     

    Any model number(s) on the hard drive label(s)?

  • by len-35,

    len-35 len-35 Jan 17, 2014 8:21 PM in response to Jan Hedlund
    Level 1 (0 points)
    Jan 17, 2014 8:21 PM in response to Jan Hedlund

    Hi Jan,

     

    I spent a couple of hours down in the shop trying to get my ext. HD to be recognized but no luck. I took a quick look at the 3 links you sent (thanks!) and I'll try a few of the tips in the morning. The 3rd one looks promising as far as telling which pins are which.

     

    The 40 MB HD I'm using in the APS case is the orginal Apple Quantum one that came with the LC. I upgraded to a 140 MB HD and put the old HD in the APS case sometime in the first year. It was the time that OS 7 was coming out and the LC had OS 6.x installed but they gave me a set of floppys for OS 7 which I put on the ext. 40 MB drive.

     

    Long story but the setup worked fine for 20 some years.

    I did check out both drives in the restored LC and they both booted normally and all of the old files were intact. More later.

     

    Len

  • by Jeff,

    Jeff Jeff Jan 18, 2014 12:12 AM in response to len-35
    Level 6 (11,559 points)
    Jan 18, 2014 12:12 AM in response to len-35

    I assume you're referring to the enclosure's three small plastic shunts that plug into the drive's SCSI ID pins A0, A1, and A2.  The SCSI ID switch on the back of the enclosure is probably a push-in or rotary type.  You may have to attempt a trial and error approach to determine the correct configuration, if you want the versatility of changing the ID via the switch.  I acquired a number of used, external enclosures back when I was using the old, SCSI-based Macs and never bothered connecting the switch.  I manually set a fixed SCSI ID of the enclosed device by installing a shunt (jumper) across the desired pins.  With a Quantum Fireball, there are three pairs of SCSI ID pins labeled A0, A1, and A2.  If no shunts are placed on these pins, the drive's ID is 0.  If you place a shunt on the A0 pins, the drive's ID would set at 1.  If a shunt is placed on the A1 pins, the drive's ID would be 2.  For a SCSI ID of 4, place a shunt on the A2 pins.  Any of these settings won't conflict with the internal hard drive's SCSI ID of 0 or the computer's ID of 7.  If you connect an external optical drive, its SCSI ID can be set at 3 - the same as internal optical drives are configured.  If the Fireball's "TE" (termination enabled) pins have a shunt placed on them, the SCSI chain will be terminated and you won't be able to daisy-chain/connect another SCSI device to the back of your APS enclosure.  If you don't place a shunt on the TE pins, the SCSI bus won't be terminated and you'll need to connect an external terminator on the back of the enclosure — if you don't daisy-chain another drive from the enclosure.  I always had more reliable operation when using an active terminator, rather than the less-expensive passive type.

  • by Jan Hedlund,Helpful

    Jan Hedlund Jan Hedlund Jan 18, 2014 8:11 AM in response to len-35
    Level 6 (9,901 points)
    Jan 18, 2014 8:11 AM in response to len-35

    Len,

     

    You may be able to verify the SCSI ID switch pinout and the connector position with an ohmmeter. One of the two rows of pins, where the wires from the switch are to be connected (or where jumpers are to be placed), may be common. To begin with, check whether a reading for the three pins in this common row against ground is close to zero.

     

    You could now try to set the switch to ID 1. This should result in a zero ohm reading between the common row and the A0 position in the other row.

     

    With the switch set to ID 2, it should be a zero reading between the common row and the A1 position in the other row.

     

    Consequently, with an ID 4 switch setting, it should read zero between the common row and A2 in the other row.

     

    All this should be in accordance with the information about jumper positions provided by Jeff.

     

    Jan

  • by len-35,

    len-35 len-35 Jan 18, 2014 9:27 AM in response to len-35
    Level 1 (0 points)
    Jan 18, 2014 9:27 AM in response to len-35

    Good morning afternoon Jeff & Jan,

     

    Thanks for the excellent information. I think I understand what you are suggesting.

     

    My Apple/Quantum HD has two jumper blocks with two rows of three terminals each. One has the three pins labeled A0, A1 & A2 along one side. As I recall, the 3 pin connector from the SCSI ID switch was plugged in here.

    A second 3 pin connector from the SCSI ID switch with 2 common wires on the outside terminals is questionable as to where it went.

     

    A second jumper block with two rows of three terminals each is near the first block and has a jumper across the middle two pins. This jumper block has never touched since day one.

     

    I'm about to go down and try both of your suggestions; will let you know the results.

     

    Len

  • by Jan Hedlund,

    Jan Hedlund Jan Hedlund Jan 18, 2014 12:53 PM in response to len-35
    Level 6 (9,901 points)
    Jan 18, 2014 12:53 PM in response to len-35

    Len,

     

    Could it possibly be something like a Quantum ProDrive 40S? A Google search for that model should give you information about jumper blocks etc (the drive in question appears to match your description).

     

    Jan

  • by Appaloosa mac man,

    Appaloosa mac man Appaloosa mac man Jan 18, 2014 12:54 PM in response to len-35
    Level 5 (4,330 points)
    Jan 18, 2014 12:54 PM in response to len-35

    Len,

     

    Jeff and Jan have given some excellent guidance.  If you are not able to quickly identify a solution, post back and we will look at the APS enclosures we have on hand.

     

    Some enclosures have three pigtails, some have all six wires in one block.  Do you have three pairs or one six pack?

     

    Ji~m

  • by len-35,

    len-35 len-35 Jan 18, 2014 8:45 PM in response to Appaloosa mac man
    Level 1 (0 points)
    Jan 18, 2014 8:45 PM in response to Appaloosa mac man

    I tried several tips without success. The HD that I'm trying to get working in the APS enclosure is a Quantum ProDrive LPS that works fine when installed in the LC. I tried Jeff's suggestion of putting a jumper plug between the A2 pin and the adjacent "ground" pin on the HD jumper block and not using the wiring harness from the APS SCSI switch. Didn't make a difference. All APS power supply voltages check OK. Cables & connectors properly installed and tight, etc, etc.

     

    Keep in mind this is a configuration that worked for years. The only difference is the main PWB in the LC which I had to replace recently. Question: Is there something on the LC board that may be responsible for the non-recognition of the external HD?? All suggestions greatfully appreciated. Thanks.

     

    Len

  • by Jan Hedlund,

    Jan Hedlund Jan Hedlund Jan 19, 2014 5:16 AM in response to len-35
    Level 6 (9,901 points)
    Jan 19, 2014 5:16 AM in response to len-35

    Len,

     

    First of all, I assume that you have made backup copies of all important files.

     

    >Is there something on the LC board that may be responsible for the non-recognition of the external HD??

     

    Even a small change can affect the SCSI chain under certain circumstances. Information about termination etc can be found in the 'Connecting SCSI devices to your Mac' article from Apple (link above). I do not have a solution to the problem but it would probably be valuable to at least be able to observe the activity on the SCSI bus. Access to appropriate utilities could help.

     

    Since both drives appear to be working OK when placed inside the LC, it should now be possible to use this computer to create system or utility floppies, if only a suitable way could be found for transfers from a downloading computer. One method could be via an external USB floppy drive connected to a more modern Mac. Another could be through a Windows PC with a floppy drive, if that computer has an application (for example, TransMac) for the handling of Mac disks. Do not hesitate to post back if you have any questions about how to make or modify floppy disks.

     

    Jan

  • by len-35,

    len-35 len-35 Jan 19, 2014 11:08 AM in response to len-35
    Level 1 (0 points)
    Jan 19, 2014 11:08 AM in response to len-35

    Hi Guys,

    I neglected to mention in my last post that the ext. HD has a second jumper block (2 rows of 3 pins) labeled WS, EP & SS with a shorting jumper across the EP pair of pins. This jumper has never been touched since I've had the LC regardless of where the drive was installed.

     

    One more thing; I assume that the termination resistor packs (there are 3) follow standard conventions and pin 1 is marked with a dot and should be lined up with the arrows on the PWB. This puts the printing of the packs facing the end of the HD with the power and SCSI connectors. I checked the value of each pin with respect to pin 1 and they all came in at 162Ω with the exception of the last pin (pin 8?) which was approx. 65Ω. Strange.

     

    Len

  • by Jan Hedlund,

    Jan Hedlund Jan Hedlund Jan 19, 2014 12:24 PM in response to len-35
    Level 6 (9,901 points)
    Jan 19, 2014 12:24 PM in response to len-35

    Len,

     

    The following appears to be valid for similar drives.

     

    WS = Wait Spin (default = no jumper = disabled = the drive starts up automatically when power is applied)

     

    EP =  Enable Parity (default = jumper in place = parity check enabled)

     

    SS = Self Seek (default = no jumper = test disabled)

     

    Jan

  • by Jan Hedlund,

    Jan Hedlund Jan Hedlund Jan 19, 2014 2:24 PM in response to len-35
    Level 6 (9,901 points)
    Jan 19, 2014 2:24 PM in response to len-35

    Also (and this is pure speculation, since I am not familiar with the exact design of your hard drive), one would perhaps have expected that the signal pins were something like 220 ohm relative power and 330 ohm relative ground if typical passive termination resistor values would be used. The following example documents could possibly be of some interest for general information.

    http://forums.seagate.com/t5/Enterprise-HDD-Terascale-HDD-NAS/SCSI-Termination/t d-p/72

    http://knowledge.seagate.com/articles/en_US/FAQ/168871en

    http://www.bourns.com/pdfs/scsi.pdf

    http://www.bourns.com/pdfs/4600X.pdf

     

    Have you at some point tested to remove the termination resistor packs from the hard drive, and instead used an external SCSI terminator (unless there is a terminator inside the case in question)?

     

    Jan

  • by Jan Hedlund,

    Jan Hedlund Jan Hedlund Jan 19, 2014 10:35 PM in response to Jan Hedlund
    Level 6 (9,901 points)
    Jan 19, 2014 10:35 PM in response to Jan Hedlund

    Len,

     

    Well, I was not considering the parallel load of all resistors in the network. So, your readings from the signal pins (not the last one) to pin 1 appear to be correct.

     

    Let us have a look at the dual terminator circuit (104) under the last link above as an example. With R1=220 ohm and R2=330 ohm, the total (parallel) resistance for only the five legs to the right would be 550/5=110 ohm. If we just look at the signal pin in the (first) leg to the left, it would then see a resistance relative pin 1 of 330 ohm parallel to 220+110 ohm. That would mean 165 ohm.

     

    For pin 8 relative pin 1 we would get 550/6=approx. 92 ohm.

     

    This was merely a quick calculation, so please let me know if something is wrong.

     

    Jan

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