To terminate the SCSI bus, the Terminator packs (whether part of a device, or a block itself) must have power (I think it's +5v) in order to properly terminate the bus. When there is no power, it's as if the terminator is not even on the chain. This causes the signals to bounce back and forth causing the noise on the bus to go higher and higher really quick drowning out any signal. This is why it's important to have power on the SCSI bus for termination.
Most of apple's newer machines could do this, some didn't (I don't think the PowerBook 145b did, since mine required a SCSI HDD to provide the power), most do. A lot of older SCSI cards back when SCSI-1 standards weren't totally set, people deviated so widely, that the SCSI Voodoo was even worse, and it was like pulling teeth to get things to work right, and depending on which shoulder you threw the salt over, good fortune might smile on you and the SCSI keeps working.
Apple especially followed this, integrating this and that, while leaving out other things that they didn't want to/feel the need to implement. Some of those were the Term power.
Since a lot of hard drives back then supplied it (external drives I mean) it wasn't much of an issue, but when several manufacturers thought "Why do we have >x devices putting power on the bus?" they pretty much stopped that. I have several 68-pin and 2 80-Pin SCSI drives that do not have their own Term power and require the card to do that.
It's quite rare for a modern SCSI drive to ship with it either turned on, or available for that matter, since about 99% of the time, the card provides the power on the bus.
Like I said, if your mac doesn't provide the power, and the Zip 100 doesn't provide the power (no external Zip 100's did iirc) so SOMETHING has to provide power, and lack of that causes issues. That can range from SCSI drives popping off the bus, to crashes (Random signals locking up the bus, or noise) or plain not showing up in the first place.
I would suggest, if you have another SCSI drive, possibly from another mac, Attach it inside the SE/30, or take the one you have, and set it to provide Term Power. I would be willing to bet that would solve your issue, especially since a lot of apple's shared the same SCSI Bus both inside and out.
Keep in mind, should you need to terminate the bus, you MUST terminate at both ends. This means the drive inside (HDD) and the last drive outside have to be terminated, but NOWHERE in between. Since it shares the bus, an extra terminator would make the signal weak, or not pass through the chain.
I seem to recall that most machines (except the IIfx, which i think is why that special black terminator was used) that apple used provide termination at the card in most cases, not sure on all. So if you had no external drives,a only internal, the adapter would terminate, and the drives inside at the end would terminate.
SCSI Voodoo is weird, but if you sit down and look at it, especially on wikipedia, you will get the hang of getting it all to work together, and be able to make it work 99% of the time.
Another thing you will want to check is cables. on the SE/30, if the cable gets damaged/knicked/etc.. you might be causing issues. You might want to try to find a different cable and use it.
Take the drive out of the SE/30 and look up the jumper settings and make sure "Term Power" and "SCSI ID (anything other than 7, the Apple SCSI adapter uses that)" is set properly. So if you internal drive is set to 7, set it to something like 0 or 1 or 2 or something (I would suggest 1) and make sure the Zip is not set to the HDD.
Connect up. Also make sure the Zip drive is on and ready before you turn on the machine. Some problems with SCSI happens because you bring up the bus before all SCSI drives are ready. So any drives you put on it externally, make sure they are powered on and hooked up before you start the machine, otherwise you can crash/hang the bus.
Try this and see if it works. failing that, read up on wikipedia, whole host of treasure troves of information!
Most of apple's newer machines could do this, some didn't (I don't think the PowerBook 145b did, since mine required a SCSI HDD to provide the power), most do. A lot of older SCSI cards back when SCSI-1 standards weren't totally set, people deviated so widely, that the SCSI Voodoo was even worse, and it was like pulling teeth to get things to work right, and depending on which shoulder you threw the salt over, good fortune might smile on you and the SCSI keeps working.
Apple especially followed this, integrating this and that, while leaving out other things that they didn't want to/feel the need to implement. Some of those were the Term power.
Since a lot of hard drives back then supplied it (external drives I mean) it wasn't much of an issue, but when several manufacturers thought "Why do we have >x devices putting power on the bus?" they pretty much stopped that. I have several 68-pin and 2 80-Pin SCSI drives that do not have their own Term power and require the card to do that.
It's quite rare for a modern SCSI drive to ship with it either turned on, or available for that matter, since about 99% of the time, the card provides the power on the bus.
Like I said, if your mac doesn't provide the power, and the Zip 100 doesn't provide the power (no external Zip 100's did iirc) so SOMETHING has to provide power, and lack of that causes issues. That can range from SCSI drives popping off the bus, to crashes (Random signals locking up the bus, or noise) or plain not showing up in the first place.
I would suggest, if you have another SCSI drive, possibly from another mac, Attach it inside the SE/30, or take the one you have, and set it to provide Term Power. I would be willing to bet that would solve your issue, especially since a lot of apple's shared the same SCSI Bus both inside and out.
Keep in mind, should you need to terminate the bus, you MUST terminate at both ends. This means the drive inside (HDD) and the last drive outside have to be terminated, but NOWHERE in between. Since it shares the bus, an extra terminator would make the signal weak, or not pass through the chain.
I seem to recall that most machines (except the IIfx, which i think is why that special black terminator was used) that apple used provide termination at the card in most cases, not sure on all. So if you had no external drives,a only internal, the adapter would terminate, and the drives inside at the end would terminate.
SCSI Voodoo is weird, but if you sit down and look at it, especially on wikipedia, you will get the hang of getting it all to work together, and be able to make it work 99% of the time.
Another thing you will want to check is cables. on the SE/30, if the cable gets damaged/knicked/etc.. you might be causing issues. You might want to try to find a different cable and use it.
Take the drive out of the SE/30 and look up the jumper settings and make sure "Term Power" and "SCSI ID (anything other than 7, the Apple SCSI adapter uses that)" is set properly. So if you internal drive is set to 7, set it to something like 0 or 1 or 2 or something (I would suggest 1) and make sure the Zip is not set to the HDD.
Connect up. Also make sure the Zip drive is on and ready before you turn on the machine. Some problems with SCSI happens because you bring up the bus before all SCSI drives are ready. So any drives you put on it externally, make sure they are powered on and hooked up before you start the machine, otherwise you can crash/hang the bus.
Try this and see if it works. failing that, read up on wikipedia, whole host of treasure troves of information!