SCSI case help

[JRL]

So I have a normal external 50-pin SCSI "ProDirect" hard drive case. Nothing strange, just a normal power supply board inside and three cables; the normal SCSI and power connector for the hard drive, a fan cable, a LED cable, and a power board connector.

Do I have to plug any of those cables in? The hard drive I'm planning on putting in (Quantum ProDrive LT) only has two.

 

[Unknown_K]

For external drivers you need 3 things:

Power to the drive

Data cable from the drive to the external connection where you connect another cable to the computer

Termination (either externally or on the drive itself)

Normally you will have extras like a cable for drive activity, and a set of cables to SCSI ID (so you can set it using the back switch) but they are not needed.

 

[JRL]

Alright, thanks. So would I need to connect the fan?

 

[LCGuy]

If its there, you may as well...it sure as hell won't hurt anything, and its probably there for a reason....

 

[equill]

You didn't mention the Macs to which the external drive may be attached. This can be significant, depending as the Mac(s) have a single internal/external bus or both internal and external buses. If there is only one bus, the external drive must have a different SCSI ID from that of any other drive in your system. Given that the purposes of external drives are often for backup or troubleshooting, SCSI ID=6 is often useful—because the system polls downward from ID=7 (the host, or the Mac itself) to ID=0, the default for a single internal HDD—to ensure that the system boots from the external drive when you select it with the four-fingered salute (control-option-shift-delete). You can therefore either connect the SCSI ID selector-switch for ease of external access/change, or be prepared to select a fixed ID directly on the drive.

If the external HDD will be used with older PowerBooks that do not provide termination power to the external daisy-chain, it will be handy to have an external HDD that can provide its own termination power, and even termination power to the bus. Quantum drives do not universally, or even often, provide this facility. Most of their narrow-SCSI (50-pin) lines have no ID selection and no power selection (the oldest), or ID selection but no power selection (the middling). Their 68-pin drives (more recent) offer a little more in the way of configuration.

If the enclosure that you cited has two external CN-50F ports, one must be occupied by a passive CN-50M terminator, as Unknown_K mentioned, unless the HDD itself offers active or passive termination on its logic board. If you use the on-board termination, the enclosure will have to be the last device in an external daisy-chain. If you don't use the on-board termination, the second CN-50F port can either have another SCSI device daisy-chained from it, or use a plug-in terminator.

The fan question has been answered by LCGuy. It is there for a purpose—no matter why it is presently disconnected—and becomes more important as the capacity, rotational speed and duration of use of the contained HDD are increased.

de

 

[JRL]

Well, the problem is that the Quantum ProDrive LT (in essence, a ProDrive LPS)'s ports for LED/SCSI control don't match the LED/SCSI termination/ for the case, even though the enclosure is a typical standard 50-pin Centronics enclosure.

 

[equill]

Can only sympathize. It's a happenstance that you will meet often when you try to shoehorn a different drive from the original into an an enclosure. The LED activity light's socket on a flying lead will almost never be suitable (usually far too massive to fit between as well as across a pin array. The misfit with the SCSI ID connector is more puzzling, as it usually concerns a single six-pin (3 x 2) array, or two 3 x 1 arrays side-by side. Perhaps your drive and the socket(s) are on different spacings (there were two) in inches (0.1) and millimetres (2)?

de

 

[JRL]

Well, I'm thinking that the plastic of the enclosure's SCSI ID connector is just too big for the ProDrive LT.

if I could possibly Dremel some of the plastic off, it would fit.