I've just put up a tk50/tk70 FAQ based on this at:
	http://www.netbsd.org/Library/Hardware/Machines/DEC/vax/tk50.html

	(It may take half an hour or so to become available).

	Many thanks Emanuel! :)

	Corrections/additions welcomed!

		David/absolute

         -=- They took away my irony, but they left my deceit  -=-

On Tue, 22 Jun 1999, emanuel stiebler wrote:

> 
> -----Original Message-----
> From: Stan Pietkiewicz <stanp@storm.ca>
> To: port-vax <port-vax@netbsd.org>
> Date: Monday, June 21, 1999 9:37 PM
> Subject: TK50/TK70 tapes
> 
> 
> >While trying to use a  TK50 tape in my MV3600's TK70 drive, the drive
> >went into read-only mode, and tar complained that it couldn't write to
> >the tape. This happened on a number of tapes, even though I eventually
> >found one that I could write to.
> >Is this happening because the tape was previously written on a TK50
> >drive??  If so, can the timing track be erased with a powerful permanent
> >magnet (and from which side?) or is an alternating magnetic field
> >needed? I'm asking about the permanent magnet because the audio/video
> >equipment dealers I've talked to don't stock a *good* bulk tape
> >eraser...
> 
> 
> Hi,
> 
> I guess, there should be slowly a TK50/TK70 FAQ ;-))
> 
> The world, how it should be:
> 
> 1.) A TK70 drive works on a TQK70 controller, writes/reads TK70 tapes, TK50
> tapes are read only.
> 
> 2. A TK50 drive works on TQK50/TQK70 controller, writes/reads TK50 tapes.
> 
> Some remarks to the "world" above:
> 
> a.) Sometimes, some people like to play with magnets/bulk erasers. So you
> can get TK50 tapes that are formatted as TK70, and vice versa. You should
> erase them and use as intended. Means a TK50 as TK50, TK70 as TK70.
> 
> b.) The TK50 tapes are also known as CompacTape (COPMAC WITH TWO 'C' !!!)
> The TK70 are known as CompacTape II.
> 
> c.) If you want to push your luck ;-))
> 
> It is possible to use a TK50 tape in a TK70 drive, after formating the tape
> on a TK70.
> 
> BUT: (It should be taken seriously !!!)
> 
> THIS IS NOT SPECIFIED !!! The TK50 and TK70 tape material is different, and
> the write current of the TK70 drive is different (IIRC, lower)
> 
> Once again, this is for playing/temporary storage only, or for BACKUPs, you
> never need again ;-))
> 
> But it works, and nobody knows why. (Magic ?)
> 
> d.) What you need for erasing a tape. A $1000 bulk eraser, or a $0.20
> magnet.
> 
> If you can operate your drive outside the computer, remove the metal cover
> of the drive, and put the magnet near the tape while the drive try to feed
> the tape in.
> 
> BUT PLEASE: DON'T PUT THE MAGNET NEAR TO THE READ/WRITE HEAD OF THE DRIVE
> !!!
> 
> If you can't operate the drive open, use the bulk eraser ;-))
> 
> e.) If you can choose between a TQK50 or TQK70 controller for the TK50
> drive, take the TQK70. It's faster.
> 
> f.) If you have problems with your TK50/TK70 drive:
> 
> Clean it !!!
> I have no real/good explanation for this, but the TK50/TK70 drives are
> better dust/dirt magnets as most of the vaccum cleaner I know. So most of
> the problems you usually can get with a TK50/TK70 are due to dirt/dust on
> the tacho/LEDs inside the drive.
> 
> HOWTO: If the drive is dirty, open the metal cover nothing more !
> and clean it carefully. There should be 4 LEDs, which should be made clean,
> and the area around. And, because you opened the drive already: there is
> this "Take Up Leader" to feed the tape in. Check it too, if it is bend, or
> broken.
> If you have to replace it, the DEC-PART-NUMBER is 74-28268.
> 
> 
> 
> That's for the moment, if there is something wrong here, sorry.
> This was written in the morning, and after the first cup of coffee ;-))
> 
> 
> Hope it helps,
> cheers,
> emanuel
> 
> 
>