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External Hard Drive SCSI ID

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I was working on my LC III (again) and tinkering with the two external hard drives I acquired some time ago. It turned out that one of them had a functional hard drive but the enclosure's power supply was not working, while the other had a perfectly OK enclosure but the hard drive itself has seized up. Between the two of them, I have put together a completely working external hard drive setup, which is great.


The problem is that the working hard drive had a small set of pins which was ripped off accidentally during the physical transfer. The pins are attached to a cable in the old hard drive enclosure, and it turns out this is part of what is used to set the SCSI ID. Without the pins in place, the external HD is apparently treated as being SCSI ID 0, since when I have both the internal HD and the external connected at the same time, the system preferentially recognizes the external. This is kind of a pain since I want to transfer what's on my internal hard drive to the external one.


I can probably reattach the pins to the actual hard drive so it reports its SCSI ID correctly, but my soldering game isn't really up to par and I'm worried about damaging the unit. Is there any other way to have the external or internal SCSI ID change so that both drives are visible by the system?


Alternatively, I have an Iomega 100MB zip drive which I know I can attach to the DB-25 port in back and store the files from the internal HD to a zip disk. However, since the external HD normally attaches to that port, it doesn't look like both can be attached at the same time at first glance. Would it be possible to chain these together like this:


Mac (internal HD disconnected) -> DB-25 to CN-50 cable -> external HD -> CN-50 to DB-25 cable -> zip drive


Would the zip drive itself also need to be terminated, or would I have to put a pass-through terminator on the second cable? I should note that the external HD has two CN-50 ports whereas the zip drive has two DB-25 ports, so I would need to get an extra cable in either case.

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Kinda gonna answer these in reverse.


Termination is needed at the end of the chain.  Whatever device you put at the end must have termination somehow.  SCSI zips are nice as they have a switch to do that so putting them at the end of the chain is great.  Anything in the middle of the chain should have no termination power or switches or they will end the chain.


You will defiantly need cables to have more than 1 device, pick the ay you want to do it so you can identify what you will need.


You can solder the wires right to the hard drive rather than trying to put pins on that will most likely snap right back off when you try and slide the cable on.  Just cut the connector off, strip a little of the wire off and solder right to where the pins were.  

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Thanks for the response. I've ordered another DB-25 to CN-50 cable since I'll need it in the long run, so in the worst case I can transfer from internal HD to zip disk, then zip disk to external HD.


Regarding the soldering, I'm assuming that soldering the wires would be only if I wanted to be able to set the SCSI ID any time I want, but if I wanted to set the SCSI ID permanently to something (other than 0 or 7), couldn't I just solder together two of the contacts together on the PCB? It seems like the contacts normally connect to this piece which has a 2 x 3 array of pins on it, where normally you would have a jumper connecting two of them to set the ID unless I'm mistaken. I've provided a diagram to illustrate what I'm talking about and make things clearer hopefully:




Would the direct soldering approach work? Or alternatively soldering a tiny length of wire between the desired contacts?

Edited by fyndr
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