O ne of the problems that can occur with porcelain base trimmers is that, when tightened, a deficiency in the plastic insulator or mica may cause the movable armature touches the fixed armature, thereby causing a short and inoperability of the circuit as shown in figure 1.
Figure 1 - sectional view of an adjustable capacitor trimmer.
One way to correct this problem is to replace the insulator, without the need to remove the component. In this case you can take advantage of the insulator of another trimmer by simply remove it. To achieve this isolator, simply remove the adjusting screw.
