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Terminating SCSI drive


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#1 spiraling

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Posted 21 December 2009 - 06:27 PM

An old SCSI tape backup that I have gave the ghost. It is a Wangdat 3100 so I went online and got a new (refurbed) from a company that specializes in doing just that. So two weeks into using the refurbed unit, it fails to eject the tape. I call them back and they ask if I terminated the drive correctly. I am not sure what they mean by that - I replaced the same model drive and the original one ran faultlessly for quite a few years, I replicated jumper settings and put it on the same slot that it was in with the same SCSI device number.

So the guys at the refurb place are telling me that the drive was improperly terminated and that's why it didn't function. They are refunding the $ but I wanted to make sure that I am not doing something stupid on my end and this the tape won't eject.


Here is the manual for the drive and it is the last in the chain.
http://www.craystone.com/dealer/page14.html


I tried to look into finding more info on termination but it seems like it is badly explained from what I've seen so I could use some clarification.

Thanks.

It reads:
SCSI TERMINATION: JP1 (Jumper Block)
Jumper JP1 connects termination power to the SCSI bus. When the two pins are jumpered, and thus installed, termination power is supplied by the drive. Without a jumper the power is supplied by the host. (The default setting is for the pins to be jumpered)

In my case the JP1 is unjumpered as it was on the original drive that I replaced. Now I am just trying to get my tape out of the drive so I can return for RMA - wouldn't just powering it and holding eject do the trick if nothing is broken on the hardware?

Edited by spiraling, 21 December 2009 - 06:50 PM.


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#2 techextreme

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Posted 22 December 2009 - 11:03 AM

To try to help and clarify, I'm going to ask a few questons.

What kind of SCSI Controller are you running?

How many devices are on the SCSI Chain?

What other devices are on the SCSI chain?

The original drive.... did it have the Termination Resistor installed on the bottom and did you move them over to the replacement?

How long is the SCSI cable?

How many connectors are on the cable?

Do you have any Active or Passive Terminators in the SCSI chain?

If you don't understand a question, please let me know and I'll do my best to elaborate.
Techextreme

"Admire those who attempt great things, even though they fail."

-- Seneca

#3 spiraling

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Posted 26 December 2009 - 09:30 PM

Tech, both drives have the termination resistors. The length of the cable is about the size of a standard IDE cable. 25 pin in two rows SCSI. I am not sure on the type of the SCSI interface besides that it is very old, mid 90s old. The cable has 3 connectors, the first one that goes to the mobo, then one empty connector and the last in teh chain is the connector that was plugged into the SCSI device.

No idea on active or passive terminators. From what I've read the drive has 3 termination resistors that are in place, just like the original drive that worked. Same jumpers in the same configuration as on the original drive as well.

#4 techextreme

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Posted 28 December 2009 - 08:10 AM

If your replacement drive was setup in the same way as your original including the terminating resistors on the bottom of the drive and also the Termination Power jumper, your drive should run just as your old one did without any problems.

If the re-manufacturer is stating that you are incorrectly terminated on the drive or the card, my question would be how do they know your improperly terminated when you do not know what scsi controller card is in your machine?

For what it's worth, I think I would send the drive back to them and have them return your stuck tape media to you. My honest opinion would be that the replacement drive had a problem to begin with or was "marginal" in their testing and that "margin" was enough for them to offer it for re-sale.

As with anything that is mechanical, parts wear as I'm sure you are well aware of. They may have missed a part or it did not show any significant errors during their testing phase and they saw no need to replace what wasn't broke. Replace the drive with another of the same make and type or replace it with something newer in the DAT family and you should be just fine.

Yes, Termination on a SCSI bus is critical to the proper operation of the drive. The only other thing that may be playing a role in your problems with the drive could be a failing SCSI controller. The only true way of finding out if your SCSI controller is failing would be to try another identical drive with the identical jumper settings and if your problem appears, you would be well off to replace your SCSI controller also.

Most DAT drives ( at least newer ones ) do have the option to eject the tape from the drive with "just power" and no SCSI cable installed. You may want to give that a try to retrieve your media.

Hope this helps,
Techextreme

"Admire those who attempt great things, even though they fail."

-- Seneca




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