Click here to purchase the entire book in PDF format. Cleaning and demagnetizing In order to ensure that your tape recorder is behaving properly, you have to clean, demagnetize and calibrate it. Cleaning the heads is an event that should happen frequently - a good practice is to clean the heads before every session to get dirt and magnetic goo from the previous session's tape off the head - you don't want anything between the record head and the tape you're recording on. Most people do this with cotton swabs and head cleaner. You could use alcohol, but this may have a tendency to dry out the rubber components like the pinch roller on the tape deck. It's also a good idea to be careful to not get the cleaning fluid all over the place around the head block (the big assembly that holds the erase, record and playback heads). This is because the cleaning fluid is also a degreaser, and you do not want to dissolve the grease inside the bearings in your capstan and pinch roller. Over time, the playback and record heads may become permanent magnets. This is a bad thing because it's the equivalent of applying a DC offset to your signal. To reduce this problem, you can demagnetize your heads using a demagnetizer. This is basically an electromagnet that oscillates with a very high-strength magnetic field, going positive and negative. You should switch on the demagnetizer when it's far away from the heads, bring it in close to the heads, being very careful to not touch the heads with the demagnetizer, then move it far away again before switching it off. Always remember that the demagnetizer is also a very good bulk tape eraser, so don't do this while there's tape in the area... You'll wish you hadn't if you do. Figure 6.66: The various parts on a typical tape recorder. The supply reel and the take-up reel are always pulling on the tape a little, just to provide tension. The capstan is the part that actually pulls the tape through the deck at the right speed. This turns all the time at a constant speed - even when you're not playing or recording. When you hit the play button, the pinch roller moves in a pinches the tape against the capstan to make it pull the tape through.