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Thread: 9-track magnetic tape unit maintenance and operation?

  1. #1

    Default 9-track magnetic tape unit maintenance and operation?

    I finally managed to get a 9-track tape unit, a re-branded CDC 92185, and I spent the weekend cleaning it up and replacing the deteriorated foam (full of 1-inch foam to help with noise, I suspect). Being a new tape unit owner, I'm now full of questions.

    So I cleaned the tape path as per the manual and fired it up. It runs and passes a lot of the maintenance and diagnostic tests, but fails on some others. One of the errors is "03", which is "ID fault", and the documentation says:

    "STU displays Fault Code 03 during Operator Test 1 due to a failure to read or write the PE identification burst at load point. The probable cause of this fault is damaged tape. The tape should be free of defects within the first six inches of tape after the BOT reflective marker."

    * STU : Streaming Tape Unit
    * BOT : Beginning Of Tape

    I get this error when I use brand new tapes (I have sealed new-old stock, 3M 703 and 700 Black Watch tapes). However, when I use a tape (also 3M brand) that came with the unit and had data on it from back when it was in service, it passes this particular test, but fails on a different test later in the procedure.

    This makes me wonder if new tapes need to be initialized or formatted in any way? Where, where, how is this PE Identification Burst written? I don't see any mention of such a process in the manuals, but I have never used an actual tape before. The description says "failure to read or write", but it does not say which, and that also hits that the test should be writing the PE Identification? Maybe since the tape with data probably has this ID already, it passes? I'm just guessing, and any information or insight would be greatly appreciated, and more questions to come for sure.

  2. #2
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    Yes--PE tapes start with an ID burst. This lets a tape drive determine the density (NRZI, PE or GCR).

    The HP intro to tape in bitsavers might help you understand. A bit dated, but very well written.

  3. #3

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    Thanks for the links, that is good info. But... How does a new tape get its ID burst? Is this something the tape drive can write, or do tapes come with the burst already written?

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    They're written at BOT by the drive. Before that, the tape doesn't "know" anything. Regardless of the certification label (800,1600,3200,6250), new tapes are all blank and basically the same (e.g. you can write and read 800 NRZI or 6250 GCR on the same tapes).

  5. #5

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    I'll keep checking the manuals, but so far I'm not seeing any maintenance routines in the tape drive for writing the ID burst to a new tape. Unless the diagnostic routine that is failing to read the burst is also responsible for writing the burst. Strange that it can write a tape full of ones, zeros, or a pattern, but it would not be able to write the ID?

  6. #6
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    Quote Originally Posted by matthew180 View Post
    I'll keep checking the manuals, but so far I'm not seeing any maintenance routines in the tape drive for writing the ID burst to a new tape.
    that is performed by the tape formatter the first time that a new tape is written

    does this drive have a Pertec or SCSI interface?

    you can isolate if there is a problem with the drive if you can find an already written 1600bpi tape

    if you're in the bay area, I can give you one

  7. #7

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    The tape is a re-branded (Honeywell Bull) CDC 92185 / 92181. I don't think it was ever known by a common model number (sure would be nice if it was). I found the correct documentation here:

    http://bitsavers.org/pdf/cdc/magtape/92181/

    It has an 8-bit SCSI interface with an HD50 connector and identifies itself as a "CDC 92185" via SCSI ID polling.

    I am not in the bay area (wish I was), I'm in SoCal. I have some tapes, 3 new, 2 that had some sort of data on them. I have also ordered some of the elusive 3M 777 tapes that are referenced in the manual. I cannot find any information about them or why they are special.

  8. #8
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    777 (or 777GP) tapes are not the best stock to use. I've had numerous problems with 777 tapes written around 1969-1978 with sticky ills. Stay away from 1980s Memorex MRX IV as well. IBM, Graham, BASF, etc. are a better choice.

    Basically, if you've got a SCSI interface, set the density to 1600PE (I think there's a manual switch or button for that), rewind to BOT and start writing. You should write an ID burst.

  9. #9

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    I need some reliable tape. Any suggestions on where to get a reel I can trust? I don't know if my problems are the head, the electronics, or the tape. I wonder if it is possible to find a modern tape that is wider, and cut it down to the correct width?

  10. #10
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    Wider tapes exist, but probably not worth the effort. I've gone through hundreds of tapes, both 7 and 9 track; generally, with a few exceptions, they're pretty robust. I note the issues with the 777 tapes only because they appear to be a problem in the jobs that I've gotten.

    Does Athana still have tapes in stock? They did, as of a couple of months ago.

    http://athana.com/html/ctape.html

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