48 TROUBLES WITH THE MAGIC LANTERN lCn. I 



Unless one has considerable knowledge of arc lamps it is advis- 

 able to get an electrician to repair the lamp. 



Short circuiting in the lamp is a rare trouble and less liable to 

 occur than almost anything else. 



GOING OUT OF THE LAMP 



71. This may be due to the stopping of the dynamo. 



72. A fuse may burn out somewhere along the line. 



73. Some connection may burn out or one or both wires may 

 be disconnected. 



74. The carbons may have burned off so that the interval 

 between the ends is too great for the current to pass. This is a 

 very common cause, and is, of course, easily remedied by the use 

 of the feeding screws of the lamp to bring them closer together. 

 If the carbons are so short that they cannot be brought together, 

 new carbons must be inserted. Always open the table switch 

 before putting in new carbons. 



Sometimes the screw holding the lower carbon is not set up 

 enough and the carbon falls down. If this is the trouble open the 

 table switch and replace the lower carbon in its proper position and 

 tighten well the set screw holding it. 



Always look at the carbons first in case the lamp goes out 

 unexpectedly (see also above 66-67, 7 an d an the causes for no 

 current 61-70). 



NOT ENOUGH CURRENT 



75. There may not be enough in the line. 



76. The line may be grounded. Test for this with the testing 

 incandescent by touching one of the terminal wires of the incan- 

 descent to some metal object connected with the ground, like the 

 metal tube enclosing the wires, a water or gas pipe or radiator, and 

 the other to one of the exposed metal parts of the conductors, first 

 on one side and then on the other. If there is a connection of 

 either wire with the ground the testing lamp will light when its two 

 wires are connected, one with the radiator, etc., and the other with 



