Abstract: A printed circuit board can be formed by a method that includes the step of cutting a circuit pattern out of a low cost plastic sheet material, and transferring the pattern onto a tape. The tape, with the pattern adhesively attached, is transferred onto a conductive film surface on a dielectric board. Thereafter, the tape is removed, leaving the pattern on the conductive film. An acid-etching step is performed on the exposed areas of the conductive film, after which the pattern is removed from the non-etched areas of the conductive film.

Abstract: In a portable preheater of the type used for burning a fuel and air mixture generated from a pressurized gas cylinder and blower, and for delivering hot exhaust air for preheating, the improvements including a warming receptacle formed to support the fuel gas cylinder and define a substantially enclosed pathway around at least a portion of a cylinder supported in the receptacle and further including means for diverting and feeding back a minor portion of the hot exhaust air delivered by the engine preheater into the warming receptacle whereby the fuel gas cylinder is maintained at a temperature to permit continuous vaporization of the fuel at a desired rate. The novel combustion chamber arrangement for dynamically interpenetrating fuel stream and air flow, stationary turbine blade for helical diversion and further mixing, and retroreflective secondary burning, coact to afford long burning time at operative temperatures using small gas cylinders of the disposable type.