Next would be how and when to know if the heads need to be demagnetized?
Terry Cummings
P.S. Thank to all in the Tape Head Project for this new forum!
There is no universal rule on demagnatizing. The general rule of thumb preached by Ampex, according to my Dad, was every 8 hours, but he said this was conserative and the much better method is to use a magnatometer. As you know, the reason you demagnatize is to avoid losing, damaging the hf portions of the tape. Playing magnegtic tape over metal parts, in theory, will cause them to become magnatized over time which is something you want to avoid around your tape. I don't own a magnatometer, I could never justify the 300 to 400 for this item just to check if I should demag my machine. My Dad told me the a lot of studios would have a magnatometer on hand to check for any magnegtic build up since you want to have that demagnatizer around your equipment only when necessary. He said that feedback he received was that in some cases it took hundreds of hours for tape playing/recording for any change in measurement by the magnatometer. In the case of a playback only situation, even more hours. So every time you clean your heads, which I do every other tape, would probably be too often. Once a year could be just fine, there is no way to tell.
You got good advice about how to do it. Clear all of your tapes away. Make sure the power to your deck is off. In fact, it is better to unplug it all together. You can destroy the heads if the deck is on. Plug it in a good 10' away move it in, go through the tape path, then the heads, be careful of the head surfaces, and (the big key) move the unit very slowly away from the unit. If you pull it away quickly it will have no effect whatsoever.
Travis
