Q Amateur • 

 Electrician 



^d Wii'Gless Operator 



Increasing the Spring Tension on 

 Vibrator Adjustments 



USUALLY the vibrator of a spark-coil 

 has only one adjustment, and when 

 the parts become worn or the screw fails 

 to do its duty some means must be em- 

 ployed to obtain results. The position of 

 the contact points requires fine adjustment 



ADJUSTING 5CREW 



■ACUU5TIN6 DISTANCE. 



GAP BCrWEEN 

 CORE AND DISK 



coil BOX, 



Paper strips placed under edge of spring-sup- 

 ports to secure fine adjustment of the tension 



for the coil to deliver sparks of maximum 

 power. The wear may be taken up by the 

 screw but this will cause a weak tension on 

 the spring. 



To overcome this difficulty on the coil 

 I owned, pieces of paper were placed under 

 the spring-support as shown in the illus- 

 tration. This made it possible to obtain 

 afineradjustmentwith the thumbscrew, and 

 eliminated the trouble. — JohxU.Leversee. 



A Concealed Rheostat for 

 Audion Cabinets 



OX audion cabinets a rheostat is gen- 

 erally used for controlling the low- 

 voltage battery current. The cabinet looks 

 much neater if the rheostat proper is con- 

 cealed and only a control-handle and 

 pointer can be seen. Such a rheostat may 

 be constructed as folbws: Procure a 

 porcelain-base battery rheostat and remove 

 the stiff brass contact-arm and the center 

 bolt. Make a contact-arm from light 

 sprmg-brass and slip it on a long batterv- 

 bolt; lock it in place by means of a flat 

 battery-nut, place on a washer and then 



insert the bolt in the hole in the center of 

 the rheostat. Place another washer over 

 the bolt, on the back side. The connection 

 with the binding post should be soldered to 

 this washer. Screw on two more flat 

 battery-nuts, adjusting them so that the 

 arm will slide evenly and smoothly over the 

 resistance element, and then lock the nuts 

 by screwing them against each other. 

 Next secure a brass rod 34 in. in diameter 

 and sufficiently long to project i in. from 

 the front of the cabinet when the rheostat 

 is placed against the back of the panel. 

 Such a shaft may be found in some old 

 telephone ringers. Drill a hole in one end 

 of the brass rod and thread the hole to fit 

 the bolt in the center of the rheostat base. 

 Turn the other end down a little in a lathe 

 and thread it so that it will take a battery- 

 nut. Screw a nut on to the bolt on the 

 rheostat and then screw this bolt into the 

 hole in the end of the shaft, locking it by 

 screwing back the nuts. Drill a hole in the 

 panel of the cabinet and insert in this a 

 bushing from an ordinary incandescent- 

 light socket. Insert the shaft and screw 

 the rheostat to the back side of the panel. 

 Make a pointer of brass, about x}/^ in. long 

 and slip it over the small threaded end of 



The rheostat is on the back side of the panel 

 and is operated from the knob in the front 



the shaft. Make a handle by cutting a 

 piece of hard rubber, or fiber, J^-in. thick, 

 in the form of a circle i3^ in. in diameter, 

 drill a hole in the center, and place it on the 

 shaft over the pointer. — Frank Sahlman. 



467 



