latest updates and/or corrections 6-17-07

First of all, don't force anything... it will just chew up the tape.
Lets start with the worst case: a reel that will not turn. Examine the
cassette and see if the tape is somehow snarled and jamming the reel.
If so, you will probably have to open it up to find out what happened
and hopefully, fix it. If the shell has screws holding it together...
it's easy to get it open. If it has no obvious screws, it's probably
glued together. You can still open it if you're careful, but you may
have to transfer the tape to another shell if the original is broken by
forcing it open. Make notes of the position and location of the tiny
parts inside as you work! If it's an important tape you're trying to
save, first open another one for practice. At some point, you'll want 
to turn the reels to advance the tape one way or the other. You can 
make a tool that fits the reel hubs from a pencil wrapped with enough 
Scotch tape to give it a snug fit. 
Cassettes are made up of two half-shells. To open a glued shell, take
a small knife and find a spot in the case along the seam that the knife
edge can penetrate. Normally the front of the cassette (careful of the
tape) provides such a starting point. While prying slightly with the
knife, tap around the edges of the shell with the handle of a small
screwdriver. As you work the knife forward, tap just ahead of it to
crack the seal. Don't force it or the plastic will crack sideways
instead of along the seal. Keep working forward until you get the shell
open. If you get stuck in one spot, try working the other direction.
The combination of applying force with the knife edge while smacking
the case at the seam will open it all the way around.
     Once it's open and you correct the problems, you can put it
back together and glue it in a few spots with a -tiny- amount of super
glue or plastic cement. CAUTION: super glue tends to wick it's way
-everywhere- and will get on the tape if you're not careful! It's best
to only apply the glue to the sides and rear of the shell... stay away
from the front. Use small strips of Scotch tape to hold the shell
together until the glue sets up, or use the tape alone to hold the
shell together long enough to copy the tape over to a new one. If you 
use superglue, as a precaution, make sure the tape is wound all the way 
to one end so if any glue does get on it, it's only on the leader and 
not the tape.
     With regards a cassette that is just "sticky" or sluggish... the
most common reason is that the tape is unevenly packed. You can see
that by looking at it. The reel pack will look bumpy, not smooth. 
Sometimes you can free it up by rapping it flat against a table top, 
first on one side, then the other. When it starts turning more freely, 
stick it in a player and wind it to the end, then back all the way to 
the beginning to repack it. It should then work normally again. Note 
that some machines will shut down while playing or winding "sticky" 
tapes because it requires too much torque from the machine. The player 
thinks it is seeing "end of tape" and shuts off.
     Cassette tapes are most difficult to splice because they're so
small. If the tape is damaged, you may have no choice but to edit out
the bad area. Be aware that audio tapes are not as critical as video
tapes as far as wrinkles going over the heads. If intact (not badly
stretched or torn), even if badly wrinkled, leave it alone... it should
still play although the sound may be a bit muffled.
     If the tape is torn, broken or stretched so badly it will not
play, try to find some splicing tape (Radio Shack has a kit with tape
and a splicing block in it) to do the job correctly. If you only want
it to last long enough to dub it over, go ahead and use scotch tape.
Trim the broken tape ends if necessary to make a neat splice. Do not
overlap the ends, but rather butt them close together and put the tape
over the two ends on the back side of the tape (so it will face away
from the heads in the machine). If you're not using a splicing block,
make sure the tape is straight when the splice is done. If it's
crooked, it will skew in the machine and may be damaged further. Redo
the splice if necessary until you get it right. Use tweezers to hold
the tape so you can cut off the excess splicing tape with scissors. If
the splice is too wide, it may stick in the guides of the player.
     One other common problem with "bad" tapes is the infamous "half
twist". When playing such a tape, you may suddenly find the voices
muffled and playing backwards. If there is a half twist in your tape,
there is another one in there somewhere! The tape must be pulled out
and rewound by hand until the second twist is found.... not fun! A full
twist means that the tape has somehow jumped over one of the reels. The
cassette will have to be pulled apart and the reel flipped over to
correct it. As an alternative, run it to the end (by hand) and redo the
end splice to the leader. It's a slow and tedious process, but I've
done it. I repair audio tapes (talking books) for the local library.

Ray Carlsen 
CARLSEN ELECTRONICS... a leader in trailing-edge technology.