[Info-vax] DLT Tape degaussing services

[Chris Scheers]

Rich Jordan wrote:
> On Mar 13, 5:34 pm, John Santos <j... at egh.com> wrote:
>> In article <gpeblu$cj... at naig.caltech.edu>, g... at ugcs.caltech.edu
>> says...>
>>
>>
>>
>>> Richard B. Gilbert <rgilber... at comcast.net> wrote:
>>>> Simply degaussing DLT tapes is not a good idea.  They have some sort of
>>>> "formatting" or a "clock track" that is necessary for proper operation.
>>>> Once degaussed, they may never work again.
>>> As I understand it, that isn't true for DLT.  
>>> (Or at least not the current versions of DLT.)
>>> It is for Ultrium (LTO) and some others, though, so one
>>> should be careful before degaussing a new tape system.
>>> Also, in some cases degaussing is required.  DLT1 uses the
>>> same tapes as a DLT IV, but the magnetic signal is different.
>>> A signal left from the older drive will not get fully erased,
>>> and will interfere with the new data signal.  
>>> According to wikipedia, the DLT formats that do use a
>>> servo track use an optical track on the back of the tape.
>>> -- glen
>> Many years ago, I got a degausser at Radio Shack for less
>> then $20 IIRC.  It is *not* a static magnetic field; it uses
>> A/C current to generate a 60Hz (probably 50Hz would work
>> just as well) varying magnetic field, and you had to move
>> it slowly around the tape, not just hold it in one place.
>>
>> It worked great for 9-track open reel tapes, and for TK50s
>> and TK70s (DLT versions -1 and 0, I think, based on the
>> current numbering scheme.)  People used to occasionally
>> try to write to a TK50 in a TK70 drive, which would muck
>> them up, or write to a TK70 in a TK50 drive, which would
>> work fine, but render the cartridge unwritable in a TK70
>> drive.  (Bad because you couldn't tell by looking at it
>> this had been done and TK70's cost about 2-3 times as
>> much as TK50's at the time.)  Degaussing usually fixed
>> both these conditions.
>>
>> No idea if it would work with a DLT IV tape or not,
>> but it sounds like a cheap enough experiment to try.
>>
>> --
>> John Santos
>> Evans Griffiths & Hart, Inc.
> 
> John,
>      unfortunately Radio Shack tells me they no longer carry those.  I
> haven't seen one on ebay this past week either (there are a couple of
> others though).  Without knowing the 'oersted rating' there's no way
> to know if one of those would be powerful enough; the manual warns
> that hand held tape degaussers may not be strong enough to do the job.

The Radio Shack unit I have is part number 44-233.  You might see if the 
store can track it down under that number.  I don't find any 
specifications on the box or manual.

I've used it successfully to degauss TK50 tapes written in TK70 drives 
and TK52 tapes (TK70) written in TK50 drives so that they could be used 
in the "correct" drives.

It is also good for degaussing DAT tapes.

I've also done some DLT IIIs and DLT IVs.  Degaussing DLT IVs for use in 
a Benchmark VS80 had mixed success, but it is not clear if the problems 
were with the degaussing or if the problems were with the Benchmark drive.

-- 
-----------------------------------------------------------------------
Chris Scheers, Applied Synergy, Inc.

Voice: 817-237-3360            Internet: chris at applied-synergy.com
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