■ i x




Figure 5—Detailing of the home-brew feedthrough capacitors. (1) The hole in the PCB base is reamed slightly with a large drill to prevent the screw from shorting to the PCB foil. (2) In C2, there are two #4 brass washer capacitor plates. One side of each is polished using fine sandpaper on a flat surface. (3) The connecting component is soldered directly to the top brass washer. (4) The dielectric between the two washers and the base PCB is 0.002 inch paper. (5) A small solder lug connects to the following circuitry. (6) The completed assembly is held together by a #2-56 bolt and nut. C1 is the same as C2 except for the dielectric (7), and the bottom brass washer has been replaced by a fiber washer (8). The dielectric is 0.001 inch polyethylene (Gladlock storage bag). It will not tolerate soldering temperatures. C1 was measured at 18 pF and C2 at 50 pF.

0 0

Post a comment