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The best way to retension old tape cartridges?

tingo

tingo

Veteran Member
Joined
Aug 12, 2009
Messages
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Location
Oslo, Norway
I have some old streamer tape cartridges (DC6150). The "good ones" I can just pop into my Wangtek 5150ES drive and do a
Code: 
mt -f /dev/sa0 retension
and then I am able to read them.
But some are not "good ones". So before I thrash them, I would like to have a go at making them operable again, at least so I can try to read any data off them.
Is there a better way than just winding them by hand?
(winding them by hand works, but takes forever)
 
How are you able to tell the "good ones" from the "bad ones" without retensioning?

I suppose you could do much of the retensioning using a rubber wheel (even an old rubber equipment "foot" threaded onto a bolt might do) chucked into a variable-speed electric drill.
 
Chuck(G) said:
How are you able to tell the "good ones" from the "bad ones" without retensioning?
Click to expand...

The "bad ones" does not retension in my drive. If I had a dive that could do "fast forward" and "rewind" commands, things would have been easier.

Chuck(G) said:
I suppose you could do much of the retensioning using a rubber wheel (even an old rubber equipment "foot" threaded onto a bolt might do) chucked into a variable-speed electric drill.
Click to expand...

Hmm, perhaps that could work.
 
tingo said:
The "bad ones" does not retension in my drive. If I had a dive that could do "fast forward" and "rewind" commands, things would have been easier.
Click to expand...

Usually the case for that is that the tension band is stretch to beyond usefulness or that it's just broken. They're the Achilles's Heel of the design. Fortunately, there is a replacement that works (at least for a time).
 
Chuck(G) said:
Usually the case for that is that the tension band is stretch to beyond usefulness or that it's just broken. They're the Achilles's Heel of the design. Fortunately, there is a replacement that works (at least for a time).
Click to expand...

Tension band? Tell me more. (I tried google, but all I got was musical bands, and orthopedic tensions bands. Hopefully, I will not need the latter ones in many years.)
 
I have several tapes that did not like retensioning. The band liked to slip and that pulled the tape itself up or down and in the end I chewed up several Apple 40mb QIC tapes for my Apple tape drive, one of which was a copy of A/UX 1.1....
 
It's a loop of polyurethane that maintains the tape tension by means of a "premissive slip" sort of property. Take a look at this image:
tape.jpg

Note the blue band going around the tape reels and over the two pulleys at the bottom? That's the tension band. Unfortunately, with age, it can break or stretch, leaving the reels to spin free. About two years ago, I talked to the good people at Imation and located a technician who was familiar with the mechanism. He said that the bands were stamped as rings from a single flat sheet of polyurethane and then flipped and stretched into place by specialized bit of machinery. He said that their lab used to have a manual version of the band-application equipment for testing.

A couple of weeks later, he called and told me that they no longer had the equipment to apply the bands and that the bands were impossible to apply without it.

One of the cctalk members sent me a couple of bands he'd discovered in an office supply store and wondered if they might be pressed into service:
69831_ENL.JPG

I used the 4¼" ones, but they're very tight. There are 6" ones available now and they might be better. Bottom line was that I was able to recover several tapes using them.
 
Thanks for the detailed and great explanation. I've just looked at one of my DC6150 cartridges, and the tension band is not broken. It doesn't appear to be stretched either (both tape reels move when I move the roller at the top, and tape tension looks good). How do I tell if it is ok or not?
 
It should be okay then. If the band is stretched, you typically see the tape start to come loose inside the cartridge when you turn the wheel. It shortly makes a real mess.

Another failure I've observed with the "Scotch" brand carts in DC600A size, but oddly not in the "3M" labeled carts is that the binder has failed where the band contacts the tape. So turning the wheel causes the oxide to peel off. Usually, the only thing you can do there is to put in a new tension band and make a new BOT. You may or may not lose some data, but it's better than no data at all.
 
Chuck(G) said:
One of the cctalk members sent me a couple of bands he'd discovered in an office supply store and wondered if they might be pressed into service:
I used the 4¼" ones, but they're very tight. There are 6" ones available now and they might be better. Bottom line was that I was able to recover several tapes using them.
Click to expand...

I have never been able to reliably get these to work. The substitutes are narrow enough that they don't reliably stay centered on the tape. I've been forced to buy what remains of NOS tapes to test and salvage the bands to deal with the problem.

Most of the tension bands on the tapes I'm seeing now have lost enough tension that they don't reliably work during a retension pass.
I've resorted to always disassembling the cartridges and testing how tight the bands are on all tapes I'm trying to recover.
 
Very interesting - I'm learning a lot from this thread!
How does one make a new BOT?
(I have a cartridge which have a tape defect close to the BOT, it looks like something took "a bite" out of the tape)
 
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