[Info-vax] DLT Tape degaussing services

[Rich Jordan]

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.