Also, when you tape the two pieces of tape together, put the repair tape on the INSIDE of the tape you are repairing. That is, put the piece of “Scotch” tape on the side of the loop of tape that faces the cassette itself. Otherwise if the tape is on the other side, it will be on the side of the tape that the rotating heads will hit when the splice goes past the heads. Even though the repair tape is very thin, it’s still enough to possibly damage the heads as they pass over the splice. If the tape is on the side of the recorded tape that is away from the scanner, it’s less likely to damage the rotating heads when it goes by. Also trim the repair tape along the sides of the recorded tape you are repairing. Use a razor blade or a pair of sharp scissors to trim the repair tape so it doesn’t stick out past the edges of the tape you are repairing. Otherwise it’s likely to get hung up on one of the various guides within your playback machine, possibly causing another break in the tape or at least causing playback problems.
The most difficult part is getting the cassette shell back together. As stated above, if you have problems getting the two doors back on the cassette, just leave them off, capture the tape and put the tape away for safety. Put the tape in a zip-lock bag for storage.
Tom