Accessing a TK50 or TK70 from RT

Rod Smallwood rodsmallwood52 at
Sun Jun 12 09:38:27 CDT 2016

On 12/06/2016 13:54, Jerome H. Fine wrote:
> >Adrian Graham wrote:
>>> On 12/06/2016 12:15, "Rod Smallwood" <rodsmallwood52 at> 
>>> wrote:
>>>>> Nearly there I think. I have loads of TK50 tapes to format.
>>>> I'm pretty sure the TK70 can only read TK50 tapes and not write to 
>>>> them...
>>> Thanks Graham
>>>     Now that sounds highly likely. Does the TK70 controller support the
>>> TK50 drive perchance?
>>> I have a TK 50 controller I can aways put that back in.
>> The TQK70 controller supports the TK50 drive, yes. If you're needing 
>> to bulk
>> erase it might be easier/quicker to get hold of a degausser then just 
>> init
>> before writing as necessary.
> I seem to remember that Adrian is correct and that the TK70
> controller does support the TK50 drive.  However, my question
> would be "WHY?" use the TK50 drive if you have a TK70 drive?
> One answer would be if you had tapes already formatted as TK50
> and you were only going to write small files.
> Since the TK70 drive (with a TK70 controller) is so much better,
> the better answer is to use the TK70 drive. However, as Adrian
> pointed out, once a tape is formatted as a TK50 tape, the TK70
> will NOT be able to write to that tape UNLESS you first bulk
> erase the tape.  Over a decade ago when I used the TK70 for
> a few years as my primary backup drive, I did a bulk erase of
> dozens of TK50 tapes and NEVER had a problem.  Be VERY
> careful with a bulk eraser which is under powered - they tend
> to break very quickly if used for more than a few minutes.
> Instead, I fortunately found an old voice coil from a speaker
> that was powerful enough (about the size of my fist) and was
> able to bulk erase TK50 tapes by repeatedly moving the voice
> coil in a circular motion in contact with the plastic container of
> the TK50 / TK70 tapes first on one side, then the other for
> about 30 seconds.  At that point, the tape could be INIT by
> the TK70 and then both TK70 read and write operations were
> possible.
> What is VERY helpful is that it is possible to COMPARE
> a BACKUP image file using BUP.SAV in RT-11 on a
> PDP-11/83 in about the same time as writing the image
> file - or about 7 minutes if I remember correctly for a full
> 32 MB image file of an RT-11 32 MB partition.
> A word of caution.  KEEP the head cleaner solution handy.
> I used wooden Qtips and rarely kept the metal cover on
> any more since the tapes shed so much that cleaning is
> needed after less than an hour of TK70 usage.  The actual
> head cleaning is fast, only a minute or two.
> If you have any more questions, please ask.  Let us know
> if you are successful.
> How is the RX02 drive coming?
> Are you still using the RD53 drive?  I haven't heard of anyone
> else being successful these days with an RD53 drive that has
> not had a lobotomy (sticky bumper pad removed from the
> head assembly).
> Jerome Fine
Hi Jerome
        Firstly one important fact that I did not know.  If you bulk 
erase a TK50 you can turn it into a TK70 tape with an INIT.
        Thank you I did not know that.

        Secondly I have made a little discovery.  We all know the tapes 
go sticky and attach themselves to guide rollers etc.
       Well its not always the tape.  I have three instances of tapes 
that would not feed or lace up where I got rid of the problem
       without doing anything to the tape at all.  In fact all 
subsequent tapes have had no problems.   It took 30 seconds and
       apart from taking the metal cover off the back off the drive I 
dismantled nothing.
       If I am right and can run a load of tapes through the drive. Then 
I'll say what I did. If I'm wrong then nobody will needlessly try my method.
       I will say its not cleaning the heads or the EOT sensors. You 
should do that any way.

       Its clear the way to go is bulk erase TK50 tapes and then to use 
the TK70 drive and controller.
       Was there ever a UNIBUS TQK70 controller?

      RX02 and a RX01 (I have one of each and a spare chassis)
     I'll be back to them when this tape situation is sorted.
     I had got to the stage where I could get commands through to the 
drive electronics

    RD53 - Yes out of a bag of scrap drives I managed to get the remains 
of a bump stop out and replace it.
                 It produced one good drive which boots RT-11 every time.

Regards Rod

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