[lug] pin numbering on SCSI drive ID select?

[Stephen Queen]

D. Stimits wrote:

> Below is a URL of really bad art I added to an excerpt from an IBM 
> spec sheet for their DDRS-39130 SCSI UW (40 MB/sec) 68 pin drive:
> http://www.battlefieldlinux.com/images/IBM_SCSI_jumper_block.png
>
> Viewed from the back in the sketch at the bottom, the power connector 
> is on the upper left of the drive, the 68 pin SCSI cable connect on 
> the upper right, and the auxiliary connector used for jumper setting 
> at the back between these. What I'm trying to figure out from the 
> manual is whether pins 1 and 2 are next to the power connector, or 
> next to the 68 pin SCSI connector? I need to set this to ID 4, so DAS2 
> needs to be jumpered, but I'm not sure if this is the 3rd pair from 
> next to the SCSI connector or the 3rd pair of pins from next to the 
> power connector. Can anyone enlighten me?
>
> D. Stimits, stimits AT attbi DOT com
>
> PS: I have this old computer completely torn apart to get the drive in 
> there, to retry again after putting it back together will be a major 
> pain.
>
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> .
>
I would guess that pins 1 and 2 are next to the 68 pin SCSI. The key to 
figuring it out is pin 10. With an ohm meter or other continuity tester, 
check to see which pins are tied to ground. Pin 10 should be ground. To 
verify, check and make sure pin 11 is tied to +5. You can use the power 
connector for ground and +5. The 2 center pins are ground, and one of 
the outer pins will be +5 ( if this is a standard disk drive type power 
connector). Since +12 doesn't go to the connector in question, just test 
pin 11 to both outside pins of the power connector. If it goes to one of 
them, then it is definitely pin 11.

Let me know if this doesn't make it clear. Hope it at least gets you 
started.

Steve Queen