Faults in Line.
In looking for a fault in a bell circuit make sure the battery is working; if only one or two cells, put the ends of two wires attached to the terminals on the tongue: a metallic taste will indicate current.
Then see that the circuit wires are firmly clamped in the terminals and no dirt or corrosion on the connections.
Next examine the push button and see that the wire connections at the springs are perfect.
If there is no movement of the bell at all when the push is pressed in, take a pocket knife or screw driver, and touch the blade across the push springs. If there is current flowing sparks will be seen when the blade breaks contact between the springs. If there are no sparks, detach the wires from the bell and twist the bare ends together. Then try again for sparks—they may now be very minute. The tongue test is good here.
If current is detected, examine the bell for the defects first mentioned.
But if no current is found at the push now the wires are broken somewhere.
First short circuit the push springs by inserting a knife blade or piece of wire so as to touch both of them. Then touch the two wires at the bell, one to each side wire coming from the magnet coils. If current is up to the bell and the coils are all right, a single stroke should result.
Replace the wires in the binding posts, clean the platinum on both contact screw and armature spring and try the adjustment. Troubles in the bell will be mostly similar to those before mentioned.
If no current has been obtained at either bell or push, and the battery is in good working order, the line must be tested for a cross or break.
If the wires are touching each other ([Fig. 35]) at some bare spot S between the bell and the battery, it will be shown by the metallic taste upon detaching one wire from the battery and laying it on the tongue T, together with another wire W from the disconnected terminal of the battery. The current will travel from the battery to the cross at S, then back along the second circuit wire to the tongue and through the short wire to the battery.
Fig. 35
If no current is obtained in this way it is probable that the wire is broken.
Fig. 36
The easiest way to find this is to take a bell to the battery and connect it between the circuit wires and the battery ([Fig. 36]).
Then with a sharp knife carefully cut away a little piece of the insulation from each wire beyond the bell and battery and short circuit the bared spots with the knife blade K. Keep working towards the push. The bell will ring each time at K K until the break D is passed, at C it will not. It becomes an easy matter then to locate it.
Fig. 37
If the bell and push are far apart, as in [Fig. 37], a break between the push and the bell may be found as shown. With the knife blade K at different points the bell will ring, but after passing the break D it will not ring.
Such simple tests as are here given can be carried out by any one, but far better results will be obtained if the reason for each is first learned.
This can be readily done by a careful study of the diagrams and text.