(07-11-2023, 06:16 PM)robespierre Wrote: The 30-year old drive that works in the beginning but soon fails is unfortunately a common occurrence. The drive spindle spins at ridiculous speeds and requires nearly perfect lubrication. Over time seals crack and lubricant migrates which cause the bearing to seize.
It sounds like some basic introductory experience with SCSI setups is where you could use more knowledge. I'll try to cover the explicit questions below, but all of this stuff is complex and there's no obvious place to start.
80-pin SCSI drives have what is known as the "Single Connector Architecture", specifically version 2, called SCA-2. A single connector makes it possible to blindly insert the disk into an array while the power is on, in other words hot-plugging. Older SCSI setups with 50- or 68-pin drives can't do that because for one thing, the power comes in on a separate plug. Hot plugging is only safe if power can be sequenced: the first pins to make contact must be ground, then power, and finally data as the plug is fully inserted. This requires all those pins to be part of a single connector.
On older drives (50 and 68 pin), the drive's address on the bus, called the "SCSI ID", is always set with jumpers. 50-pin drives have 3 jumpers (selecting an address from 0–7) and 68-pin drives have 4 (selecting an address from 0–15). The SCSI ID must be unique on that bus. Some computers have multiple SCSI busses.
With SCA-2, another method of selecting the address is possible, called geographic addressing. In that case, the ID comes through the connector itself from the backplane. So if any drive is plugged into slot #4, it gets ID 4, etc.
The Indigo2 is just barely old enough to have an awkward mix of both the old (50-pin drives) and the new (a single connector with geographic addressing), but the proprietary sleds are in between and create some "impedance mismatch". The sleds plug into the backplane by way of an 80-pin connector that is basically the same as SCA and the SCSI ID is set according to which slot the tray is in. But since the normal drives are 50-pin (both hard disks, floppies, and tapes are supported) and set their SCSI IDs with jumpers, there had to be a cable adapting from the ID pins that are part of the 80-pin connector, to the jumpers on the drive.
In order to put an 80-pin SCA-2 drive into an Indigo2 sled, there are two layers of adaptation: first from the sled's 80-pin connector to the 50-pin narrow SCSI header, and second from that to the drive's 80-pin SCA-2 connector. This double-adaptation creates issues for the SCSI ID because it has to be split off and then back in again. If your drive has a provision for the tray's SCSI ID cable, you could try using it and removing all other SCSI ID jumpers. Setting the ID using jumpers anyplace in the Indigo2 defeats the geographic addressing!
On your adapter PCB, there is a diode and a pad labeled "F1" for fuse, but instead of a fuse there is a wire link. That makes me uncomfortable.
Makes sense, thank you for the info! Yeah, again, this is literally my first time experiencing/dealing with SCSI myself - before this, it was just stuff I heard vaguely from friends and other techies. I knew IDs needed to be unique, but that's probably about it. And oh
god, that's supposed to be for a fuse?! I guess the few cents required to shove one in there would've cut into the manufacturer's profit margins too much :V
But anyways, I've managed to scrounge up a card and a 50 pin cable. While the only system I have that can accept this card is having some problems of its own, I used a copy of MS-DOS and fdisk to confirm that it can detect the old drive (although I obviously can't do much with it), but not the new one with the adapter.
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EDIT (5 August 2023): So it's been a while, but I figure I'd update how my situation is at this point. The same day I made this post originally (11 July), I did some research, found an adapter that I heard better things about, and found the website that sold it. I ordered it... and it still says the order is pending to this day.
I ended up giving up on waiting and just ordered a ZuluSCSI, and... I think I really should've just done this from the start. There were a few minor hiccups at the start, but I disabled a few features (SCSI-2 and synchronous SCSI mode), re-did my blank hard drive image so it fit the expected disk geometry, and I was off to the races. It even played nice with my CD drive, so I'm pretty happy.
I might end up attempting to use a real SCSI drive at a later day, maybe if I end up actually getting that adapter I ordered - but for now, I've got a working Indigo2 again, and that's all I really wanted. Thank you all for the help, advice, and info about SCSI you've given me!
NEED -> 
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