Yesterday I was working to identify a group of SOT23 transistors that I had just salvaged from a circuit board. After crossing numbers and coming to a good guess of what the transistor was I used the analog meter to check the junctions. With this technique it is easy to confirm whether a transistor is an NPN or a PNP type. The non-slip probe tips make this testing much easier on the lose transistors as I can lock onto one leg and then probe the other two legs without slipping off my contact points. After doing this with a couple transistors I found myself fighting with a new phenomena. Apparently the non-slip tips had become magnetized.



This made positioning and release of contact more difficult and frustrating. One would probably not notice the problem unless the parts being probed are lose, light, and have ferromagnetic leads. This was the first time that I had noticed this problem.


I remembered many years ago that another magnetization problem was when the heads of tape recorders became magnetized and slowly damaged the tapes. Our procedure at that time was to routinely demagnetize the tape heads using a tool that was not surprisingly called a tape head demagnetizer. This was a coil of wire that could be plugged into the mains 60 HZ supply with a ferromagnetic armature that tapered to a dull point on one end. The point would be placed on the tape head and then slowly moved away to a distance of several inches. The armature would alternately apply north and south fields to the head and as the distance increased the fields would weaken until the residual magnetism of the head would approach 0 Gauss.


The head demagnetizer is a tool that I had not used in perhaps 30 years but it still was in the shop on the shelf behind my tool cabinet. This is what it looks like complete with 40 years of scars.



I applied the demagnetizer to the non-slip tips, using the same procedure I had learned to use on the tape heads, and the magnetism of the non-slip tips diminished to where they no longer would attract or pick up the SMD transistors. Since there are many of the engineers on the element 14 forum using my non-slip tips I wanted to make sure I brought this potential problem and solution to your attention. If you don't yet have a set of the tips and want to get a set check with Neil at Tag-Connect as he is marketing them at this point.