4 ms·A magnet works as well and doesn't affect the lifespan of the tape as much.by sp332 3y agoA magnet works as well and doesn't affect the lifespan of the tape as much.ars 3y agoIt would be VERY hard to erase just a small portion without damaging the rest.sp332 3y agoI have not done this myself, but I had a friend who did. You just pull out the part you want to erase, run a magnet past a few times, then wind it back up.