DAT tape snapped or broken and need fixing / repairing?
Thanks to Dave for this one! Should've put this in here long ago...
Where is the break on the tape? If it's at the beginning or end, it's much easier to fix; if it's in the middle it's doable but you're a) going to have diginoise where it's spliced together and b) going to want to run a clone of it at the same time (which also risks gooping up the heads of your deck). Here's what I did when one of my tapes broke at the beginning.
Make sure you have a clean, clear surface to work on.You'll need some tiny screwdrivers (the screws are Phillips head but if you have a small enough slot screwdriver, that'll work too) and a pair or two of tweezers. If you touch the tape at any point, you'll deposit oils on it from your skin and just put more diginoise on your tape. By using the tweezers (which you might want to clean off with denatured alcohol to get any residue off) you'll still get some noise but they're more exact
Now you're ready to open the tape up. There are two screws that you can see when the shutter is closed, and two more that you have to slide the shutter open to see. Once the screws are out, flip the tape over so that the window and brand name are on top, and carefully remove the lid. The whole top will come off in one piece, as will the end piece that flips up to expose the tape; if you do it the other way all sorts of stuff will come falling out. Not good times. Bad times.
From there, it should be obvious how to get at the tape - it might be a good idea to take a digital picture of the tape so you remember how it all goes together as well as to remember the tape path. You could also just have a blank on hand to open up and compare - that's what I did. Take off the plastic piece with the teeth that hold the cogs in place, trying to keep the spring with it. The clear plastic sheet comes off next, and then you're left with the cogs sitting in their little depressions. Be careful with the copy-protection door too; it falls out really easily. Basically, don't move anything you don't have to.
Now, if your tape snapped at the beginning or the end, what I would do is take the cog with the unrecorded part on it and remove all the tape from it. There's a section of the cog that slides out from the rest of it, which holds the end of the tape in place. What you're going to do is put the snapped end in there and then re-spool the recorded part of the tape. It's a little tedious with tweezers but easier than the second situation...
If your tape snapped in the middle, it's a little trickier but still doable. I cut the thinnest slice of Scotch tape I could and put it on the back of the snapped parts. It's very tough to line the tape up properly to do this - not enough and you're leaving adhesive exposed to your heads; too much and you're overlapping. I'd suggest trimming the Scotch tape with scissors so the ends aren't "toothy" from ripping it off the dispenser - if one of those "teeth" sticks up on your reassembled tape, it can goop up your heads. I'd also suggest putting the Scotch tape adhesive-side up on your working surface, sticking one end of the DAT tape to it, and then guiding the other snapped end into place. If the tape really got chewed up, you've got the tough decision of playing through it or snipping a little bit off - mine was fortunately a clean break and it matched right back up without problems.
Once you get that done, reassemble the tape, cross your fingers and toes, and reload it into your deck. I'd suggest a home deck as it's likely to be less finicky and more forgiving of a hacked-together tape, but if your portable is all you have, go for it. I'd then run a clone of it rather than trying to transfer the snapped tape, because if your transfer screws up somehow, you've brought the bad spot over your deck's heads, which you don't want to do any more than necessary.
That's about all I can think of at the moment; I've only done this once and had success and it's not a task I'd wish on anyone...