Not 8 Tracks Part 4 Magnetic Tomfoolery

I hope you enjoy the latest in my series of 8 track videos about demagnetizing the tape head. Dont forget to watch parts 1 2 3.

Unfortunately I did get a little bit overexcited and forgot to explain the reason why you should consider demagnetizing tape recorder heads. Please see the explanation below and check out Simon Spiers excellent YouTube channel.

Demagnetising tape heads.    • Demagnetising tape heads.  

As Always Many Thanks
Chris - The Man With All The Gear


DEMAGNETIZERS AND DEMAGNETIZING

The purpose of a demagnetizer is to remove the residual magnetism that builds up on the tape heads, and all metal parts contacted by the tape, as a result of magnetic fields running across the tape. This is the same principle that occurs when you rub a nail with a magnet, causing the nail to become magnetized. Residual magnetism will erase the tape over time, beginning with the high frequencies first; extreme levels of residual magnetism will increase distortion and noise.

A demagnetizer applies a strong magnetic field strong to totally magnetize the part, then reverses the field rapidly to cancel out the magnetism. A demagnetizer runs on 60 (50) Hz AC, so the north and south poles of the magnetic field reverse 120 (100) times a second. The magnetic field’s strength must then be very, very slowly reduced until it reaches zero by slowly moving the demagnetizer away from the heads and tape guides. Effective demagnetizing applies the strongest possible magnetic field to all metal tape path parts. This requires that the demagnetizer’s tip makes close contact with the parts, because a magnetic field’s strength lowers with the square of the distance. So, choose a demagnetizer that creates a strong magnetic field, the stronger the better.

Turn the power off on the tape recorder or duplicator. Demagnetizing with the power on can damage the recorder’s circuitry.
Turn the demagnetizer on 3-feet (one meter) or farther from tape or tape machines.

Move the demagnetizer in, very slowly, so its tip touches the head(s), guides, and the capstan.

Move across the surface of each part, and from one part to the next, very slowly and smoothly. If you accidentally move quickly, go back over that part.

After you have gone over the surface of every metal part in the tape path, very slowly and smoothly
move the demagnetizer away from the recorder until you are at least 3-feet (one meter) away.

Turn off the demagnetizer.

The only way you can cause damage while demagnetizing would be to leave the recorder’s power turned on, or to shut off the demagnetizer while it is close to the recorder or to tapes, or to move the demagnetizer quickly or jerkily. need to move the demagnetizer toward and away from the recorder slowly.

Compiled by: Kermit V. Gray
KVG Labs
16371 Lake Point Drive
Bonner Springs, KS 66012
USA