> > I will make a note of that.  I ate another TK50 cartridge, again,
> > last night, because it stuck.  That retensioning is getting to be
> > important.  The tape unrolled itself all over the inside of the
> > BA123 case.
> 
> Maybe you've already done this, but I'm sure I've read on this list that
> is (or are) some optical sensors in the TK50 which tend to get covered in
> dust over time.  I don't have a manual, nor a tape drive to look at right
> now.  You might take a look at opening and cleaning any dust out of the
> drive to see if it'll behave better.

The sensors and the heads are the first things I clean, in addition to
the entire transport, when I first get it.  Then, religiously, I clean
the heads every few tape passes (10 or so).

> In this case, I'm just not sure that retensioning the tape would solve
> your problem.  I'd also be kind of wary about erasing all your tapes
> before writing to them.  Given that most of the TK50 media anyone will
> come across this days is fairly old, you'll likely end up wearing out
> tapes faster and depositing more metal oxide on the TK50 drive's tape
> head than necessary.

The tape transports are working fine, on tapes I have previously used.
On new tapes (used, surplus, old stock, etc.) I am getting a lot of
sticking on the tapes in the cartridges as they work.  It is not
the transport and probably is not the plastic physical reel inside
the cartridge, but seems to be layer to layer sticking between layers
of tape.  Places that stick drag down the speed of the of the reels,
alert the speed sensing mechanism, and the tape clunks to a screeching
halt with a loud clunk.  Then, the fun begins.

Retensioning is the ONLY cure for such shennanigans.  I am half
tempted to make up a dummy TK50 transport out of a junked one,
with a motor driven or hand crank takeup reel so I can manually
retension the tapes.  Crude, but it might be the only effective
cure.

Since I clean the heads so often, I am not worried about oxide buildup.
That does not seem to be much of a problem, although some slight traces
do appear on the cleaning rag, after 10 or so passes.  And, some tapes
appear to shed more than others.

Note that there is a recall on DEC Compactape cartridges of some
series.  I ran across that in an old DECnotes somewhere.  Apparently,
the manufacturer used the wrong oxide, and the bad tapes will
actually sandpaper the heads off.  No fun.

I clean with floppy head cleaner or isopropyl, using a soft cotton
t-shirt scrap.  It requires manually powering down, moving the heads
up off the guide pins, and physically wiping the head clean.  Crude,
and not the standard cleaning cartridge, but it works fine.
 
> You didn't happen to cut your teeth with tape drives on something like
> one of the PC based Colorado 250 cartridge drives did you?

I cut my teeth on paper tape, 9 tracks, and 1/4 inch streamers on AIX
boxes, and earlier junk.  Never used one of those Colorado things, but
I hear they had all kinds of problems, so mostly avoided them.  I have
about 1000 1/4 inch cartridges of various sizes that I use on most of
the old stuff, plus the 9 track reels.  Of all of them, the TK50 is
the absolute worst..... with the tiny IBM 3.5 inch cartridges second.
In my hands I will take a 9 track first, a 1/4 inch streamer second,
and pray a lot that the rest is readable and works when I need it.
The old 9 track stuff I never have problems with.  The old 1/4 inch
streamers only give problems when the rubber drive capstan wheels
decompose with age.  The rest... pray, pray often, and find a rabbit's
foot or lucky penny to rub, as needed.....(:+}}...

Bob