CHAPTER I.

DIRECT LINE.[1]

Bell Doesn’t Ring at all.

May be caused by any of following:

1st. Condenser open. 2d. Ringer open. 3d. Hook contacts crossed. 4th. Desk stand cords or induction coil crossed. 5th. Extention bell open. 6th. Ringer short-circuited. 7th. Trouble at central office.

1st. When condenser is open you will get weak hook clicks and side tones and hearing very weak. Prove by short-circuiting the condenser at the lugs with a test cord, which should make the ring of the bell and hearing O.K.

(While the condenser is short-circuited you will get only one hook click.)

2d. Only one hook click, the side tones normal, and the failure of the ringer armature to move when you raise or lower the hook, indicates that the ringer is open.

Prove by replacing the receiver on the hook and then bridge across the condenser lugs with your head receiver; if you do not get a good click every time you make contact, the ringer is open.

Or you can make the following test; open the strap at the top of the bell, then short-circuit the condenser lugs with a test cord; then connect one side of your head receiver to one of the line binding posts, and feel with the other side on the terminals of the ringer; if you get battery on one terminal and not on the other the ringer is certainly open.

3d. Only one hook click, side tones normal, failure of the ringer armature to move when you raise and lower the hook, and the receiver in circuit while the hook is down, indicates that the hook contacts are crossed together. When this is the case, the bell will ring poorly or not at all, and the ring can be heard in the receiver when the hook is down. Open the receiver circuit at one of the receiver binding posts, this should allow the bell to ring all right.

4th. Red and white strands of desk stand cord or primary and secondary of induction coil crossed together will generally cut down hearing; it may or may not cause only one hook click, and may or may not put battery through the receiver, and may wholly or only partly prevent the bell from ringing. Disconnect the strap on top of the bell and test with your head receiver from the G post to the L2 post; if you get battery there is a cross; disconnect the red and white strands of the desk stand cord, this will show whether the trouble is in the desk stand cord or in the bell. If it is in the bell, disconnect No. 2 and No. 4 terminals of the induction coil, and test again, to prove certainly that the trouble is in the coil itself and not in the wiring.

5th. If there is an auxiliary bell, and it is open, the set will test as though it had an open ringer. Test by short-circuiting the L2 and G posts, which cuts out the auxiliary bell and makes it a straight set for the time being.

6th. If the ringer is short-circuited you will get battery through the receiver, which can be detected by listening while you short-circuit the receiver binding posts with your screw driver blade. To prove, disconnect the bridge from the top of the bell, and connect the two line wires to the L2 and G posts instead of the L2 and L1 posts; short-circuit the condenser lugs with a test cord, and then bridge your head receiver across the ringer terminals; if the ringer is all right you will get a heavy click, if it is completely short-circuited you will get no click at all, if it is partially short-circuited you will get a partial click.

Bell Rings Weakly.

May be caused by:

Poor adjustment of armature or gongs.

Pivot screws too loose or too tight.

Clapper rubbing on guard.

Wiring interfering with the clapper stem.

“Whiskers” on the magnet heads.

Magnet heads sticky or gummy.

Desk stand cord, induction coil, or hook contacts crossed.

One or both coils of the ringer partially short-circuited.

Polarizing magnet weak.

Carbons in protector dirty and generator current jumping across them.

Trouble at the central office.

Bridge on the Line, Steady Light at Central Office.

Prove whether the trouble is in the instrument or not by disconnecting both sides of the line at the top of the bell and going in with your head receiver. If you get central the trouble is in the instrument and the same will be found either in the wiring, desk stand cords, or the hook. If opening the strap (see diagram No. 1) does clear the trouble, the leak is across through the ringer, and must be due to:

1. Receiver contact of hook not breaking. If this is the case, opening the receiver circuit at one of the receiver binding posts will clear the trouble temporarily.

2. White and green strands of the desk stand cord crossed together. If this is the trouble, disconnecting the cords from the bell will clear it.

[Illustration: Fig. 1.]

3. The condenser must be short-circuited if the trouble is not in the hook or cords; if the condenser is completely short-circuited, there will be but one hook click, but often there is enough resistance in a condenser short-circuit to give both hook clicks. To make sure that the trouble is in the condenser itself, and not in the wiring, disconnect one terminal of the condenser and go in series with your head receiver.

Instrument Entirely Dead, Nothing can be Heard in the Receiver.

See first that you have battery at the top of the bell.

The trouble may be due to:

1. Receiver circuit open. 2. Receiver short-circuited.

1. If there is an open in the receiver circuit, it may be in either the receiver itself, the receiver cord, the white strand of the desk stand cord, the receiver contact of the hook, or the secondary; bridge your head receiver successively around these parts, when you bridge around the open you will get the side tones in the head receiver.

2. To prove whether a receiver is short-circuited or not, connect your head receiver in series with it; if the head receiver responds while another receiver in series with it does not, the other one cannot be open, and therefore, must be short-circuited.

Transmitter out of Circuit, but Hearing not Entirely Cut Out.

May be caused by:

1. Open in green strand of desk stand cord, transmitter or transmitter wiring.

2. Transmitter short-circuited.

3. Red and white strands of desk stand cord crossed together.

1. No hook clicks, transmitter entirely dead, but can hear induction on the line, and can hear the effect of short-circuiting the line at the top of the bell indicates an open. Locate by connecting one terminal of your head receiver to the L1 post, and feeling with the other terminal successively on the several points of the transmitter circuit from the L2 post to the hook; as soon as you pass the open you will cease to get battery through the head receiver.

2. Strong hook clicks, transmitter entirely or nearly dead, but can hear induction on the line and the effect of short-circuiting the line at the top of the bell, indicates transmitter short-circuited. Open at the transmitter and put your head receiver in series to see whether the trouble is a short-circuit inside of the transmitter head, or a cross of the transmitter cord or the green strand of the desk stand cord with the frame of the desk stand.

3. Two hook clicks, but the transmitter dead and cannot hear induction on the line, and cannot hear the effect of short-circuiting the line at the top of the bell, and bell rings poorly or not at all, indicates red and white strands of the desk stand cord crossed together which short circuits the receiver while the hook is up. Disconnect the strap at the top of the bell, and test as previously directed from the G post to the L2 post; if you get battery the cord is crossed.

Transmission Poor.

May be due to:

1. Transmitter packed or otherwise bad.

2. Red strand of desk stand cord, primary, or hook contact open (in which case the hearing will also be poor).

3. Primary or secondary reversed.

4. Primary and secondary crossed together (this will also affect the hearing).

5. High resistance in the line or instrument.

1. When a transmitter is believed to be packed, call the wire chief, being very careful not to shake it up or jar it, and get him to note the way it transmits; then shake it up thoroughly, and see what the effect is on transmission. When a transmitter is suspected of packing but you fail to catch it in the act, you can sometimes pack it by blowing gently into the mouth piece for a minute or so; but in making this test be careful not to condemn a good instrument, as almost any transmitter is liable to a certain amount of packing, and will come up stronger immediately after having been shaken up.

When a transmitter is suspected of being otherwise defective a sure test can be made by temporarily swapping faces with some other instrument that is all right.

2. Only one hook click and weak side tones indicate primary or red cord open. Connect one terminal of your head receiver to the L2 post and test with the other successively on the L1 post, No. 1 and No. 2 terminals of the induction coil, red cord post in desk stand, hook spring, and hook; as soon as you pass the open you will not get battery.

3. Examine 1 and 2, and 3 and 4 of the coil to see that they are not reversed, that is, see that the numbers of the coil terminals correspond with the numbers of the lugs that they connect to. If the coil is reversed internally, so that the numbers correspond but nevertheless one of the windings is wrong, it can only be detected by the man at the other end. Call up the wire chief or go to another instrument yourself and listen to the transmission from the suspected instrument; if the coil is reversed the transmission will be muffled. Prove by reversing either the primary or the secondary, which should clear the trouble.

4. Test as previously directed for primary and secondary crossed together.

5. Get the wire chief to test the resistance of the line, or test it yourself as follows: Bridge your lamp on at the top of the instrument, the lamp will burn rather dimly on an ordinary line, very dimly if it is a long line, or an extension line from a private branch exchange with a high resistance drops and retardation coils. (In the latter case the test can be made better after the operator has plugged up the line.) Next connect your line in series with the instrument, take the receiver off the hook, and compare the brightness of the lamp while the instrument is in circuit, and while it is cut out by short-circuiting the L1 and L2 posts. If there is much difference noticed there is a high resistance in the instrument. Forty ohms is a fair average for the resistance of a central battery instrument, but it may be higher or may be lower, it may run below 30 ohms. About 16 ohms of this is in the primary and the rest is in the transmitter.

[Illustration: Fig. 2.]

To prove that there is no resistance in the soldered connections or hook contact, short-circuit both the primary and the transmitter; this should cut out all of the resistance and completely short-circuit the instrument, so that you will get no battery from L1 to L2 posts when the hook is up.

The resistance of a 24 volt test lamp is somewhere about 400 ohms cold and 240 ohms hot.

Hearing Poor.

May be due to:

1. Receiver bad.

2. Receiver cord or white strand of desk stand cord bad.

3. Condenser open.

4. Primary and secondary crossed together.

5. Primary short-circuited.

6. Secondary short-circuited.

7. High resistance in secondary circuit.

There will be two hook clicks with any of the above troubles, but one of the clicks may be cut down more or less.

1. Examine the receiver for dented diaphragms, “whiskers” on the magnets, magnets too close to diaphragm, or magnets weak; test by putting your head receiver in series with it and comparing the hearing.

2. To test the receiver cord and the white strand of the desk stand cord, put battery through them and listen in the receiver for a cut out or scratchy sound while you shake them. Short-circuiting the condenser with a test cord puts battery through the receiver and its cords when the hook is up.

3. If the condenser is open the ringer usually will not ring, but sometimes you can ring through a condenser that you cannot hear through at all. Test by short-circuiting it with a test cord.

4. Primary and secondary crossed together will usually short-circuit the ringer and prevent your getting a ring. Test as previously directed.

5. If the primary is short-circuited bridge your head receiver around it; you will get no click when the hook comes up, and no side tones. If the primary is all right you will get both clicks and side tones in your head receiver.

6. A short-circuited secondary can be tested by exactly the same method as is given above for testing the primary.

The above tests work very well if the primary or secondary is completely or nearly short-circuited, but if the short circuit is only partial it is very hard to detect. If you are in doubt, change the bell temporarily for another bell that is all right or change the induction coil, and compare results.

7. To test for a high resistance in the secondary circuit, put battery through it by short-circuiting the condenser with a test cord while the hook up, then listen in the receiver while you short-circuit successively the receiver hook contact, the two sides of the receiver cord, the white strand of the desk stand cord, the wiring from receiver cord to secondary, from secondary to condenser, and from condenser to L2, and the secondary itself; when you short circuit out any part of the circuit that contains resistance, such as the secondary itself, more battery will flow through the receiver, giving you a click.

An instrument in which the ringer is not connected, will, of course, give but one hook click.

Reversals in the connecting up of desk stand cords may cause only one hook click or poor hook clicks, poor transmission, poor hearing, transmitter nearly dead, etc., according to the combination in which the three strands of the cord are connected.

If the ground side of the line is open outside the set may be put in temporary service by working to a local ground.

If the induction coil is bad, temporary service can be given, if necessary, by putting the transmitter and receiver in series, and properly poling the receiver.