Unable to hear on phone

[Paul Boomer]

 Hi,

I'm back again, life got in the way.
I still have the problem of all of a sudden I can't hear anything on one of my wall phones. I had posted a picture of the back of my Kellogg mouthpiece and it was recommended I try getting a new set of rubber washers because mine were pretty deteriorated, I got those from TelePlay but that made no difference.
Someone had asked if I could hear myself in the earphone, the only thing I can hear is if I lower the hook I hear a click, I can hear a very slight hum and the phone has batteries not a transformer. 3.5V.
I have a spare Kellogg phone and I tried switching the mouthpiece but no change.
If the house calls the barn(shop) the bells ring but no sound. I can ring the house also.
I tried thumping the mouthpiece to shake up the carbon crystals but nothing happened.
I'll include some pictures of the inside of the phone if that will help anybody's diagnosis.

I hope somebody can help, it was a really handy intercom, when it worked.  Paul 

[Paul Boomer]

 Hi All,

Just bringing this to the top to see if anybody has some ideas of what I should check next  Thanks Paul

[paul-f]

Since it worked previously, the question is: What changed to make it stop working?

Some things to check include:

   
• Are any terminals loose or wires bent or moved to short on adjacent metal?
• Have any wires gone "open?" (Electrical connection between wires and terminal ends failed.)
• Are mechanical switches working properly? (Contacts in good alignment and clean.)
• Are the batteries still providing sufficient voltage?

With vintage wiring, you can't always trust that wires still conduct properly. If all else fails, you might consider disconnecting components and doing a continuity check on each wire. It's rare, but I have found several wires that visually looked good but did not connect electricity.

[Paul Boomer]

 Paul-f,

I ran a piece of paper through all the contacts of the switches I could find and checked for loose connections, the Batt voltage is 3.5V but I haven't Ohmed out all the wires yet.

Nothing had moved except the crank and the earpiece for the last year and it just quit working, so I opened the door to check voltage and it was fine, so that was the first time even the door was opened since I put the Batt. in a year ago.

I'll Ohm the wires, do you know what the resistance in the coils should be, or is it if there is any continuity at all they are good?   Paul

[AE_Collector]

How many batteries? 2 batteries would be ~3v and 3 batteries would be ~4.5v. I have no idea how fussy they would be about voltage but could the phone have worked at 4.5v and quit when the batteries dropped to 3.5v?

Terry

[dsk]

1) Do you hear the other phone in your earpiece, but not yourselves, or just no voice at all?

dsk

(Number for later use)

PS
Under will you see a typical circuit diagram for magneto telephone, yours may have slightly differences but no important.

The green short across the line terminals are for testing, or may be the line and the other telephone. Without any connection between these 2 terminals, no(, or almost no) current may travel trough your receiver, and it will be "dead". Just follow the red-ish lines.   Any current applied to the line terminal (in off hook state) should be heard in some way in the receiver.

The blue lines are the transmitter current path, and if you put in a telephone receiver in series in this circuit. (e.g. where you connect the batteries) you should hear what is spoken in to the transmitter.  These tests are good to determine if the problem is on the speaker, or the receiver side of the induction coil.


DS

[Dan/Panther]

Check the wiring between the door and the inside. Every time the door is opened you are flexing those wires. One may have finally broken.
When you lift the receiver and turn the crank do the bells ring ?

D/P

[Dan/Panther]

Also, maybe obvious, but have you checked the batteries ?

D/P

[rdelius]

You might try disconnecting the transmitter (one wire).you should hear  a pop in the receiver esp if you short out the l1, l2 terminals.Disconnecting one side of the batteries should do the same thing

[Paul Boomer]

 rdelius- If I click the receiver hanger I can hear a click but I wouldn't call it a POP.

AE Collector- The batt is a gel cell 3.V, I didn't want the corrosion chance.

D-P- The bells don't ring when the phone is cranked, but they never have since I got the phone and it worked fine otherwise so I wasn't worried about it, haven't tried with the receiver off. Will do.

DSK- I cannot hear the other voice at all but the phone will ring when the house calls. They can't hear anything either but I can ring them and the bells are normal volume. I'll try the jumper.

When checking the wiring what should the resistance be through the coils, or does it matter as long as there is current through them?

Thanks to everybody.   Paul

[rdelius]

You do hear something so the primary circuit (tx,batt and i/2 ind coil are intact.You could substitute a modern tx capsule .you have tested the rec by touching the termills haven't you?

[dsk]

Since you don't hear the other party, but your phone rings, the green jumper will probably have no effect, the fault is probably inside the phone, it may be as easy as bad contact in the hooks-witch, or a broken wire as someone mentioned earlier. 
Us your ohm-meter and trace the circuit from line to line following the red lines.

dsk

[Paul Boomer]

rdelius,

I know nothing about these phones so these are probably stupid questions but,

1.  What's a tx capsule?

2. Which terminals?   Paul

[rdelius]

touch a battery to rec (receiver) terminals  you should hear a click in the receiver.TX=Transmitter ttry a modern transmitter in place of the old one.just cilpping in the circuit

[dsk]

If you use the battery (disconnect) and connect one wire to the line terminal marked A on the sketch.
Use the other wire and touch C, you should hear a load pop, if not move wire from A to B. If you get the pop now, but not on the first test, the wire between A and B is broken, (not likely), if yes keep on moving the wire from C to D, E and F. When the pops stopping you will know the faulty wire/bad contact is between the last test point, and the one before that.
If you get no pop in the receiver when testing between Band C, the receiver, or cord is faulty.

dsk