Rotary phone question!

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KamPutty
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Rotary phone question!

Post by KamPutty » Sat Sep 02, 2006 3:19 pm

Hi all,

I got a rotary phone from a friend, and it works, but I cannot get it to ring.

The phone line is spliced to a "standard phone jack" (sorry, forgot RJ number).

Now the original part of the phone line has 3 wires.

RED
YELLOW
GREEN

The RED and the GREEN are spliced to the 2 wires on the phone jack. Now, thats cool with me, since it meets my limited knowlegde on telephony, the Tip and Ring needs where met.

The YELLOW wire is not connected. :shock:

Image

Whats the YELLOW one for? :???:

...and it works!...

~Kam (^8*

stevech
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Post by stevech » Sat Sep 02, 2006 6:10 pm

what you have is correct. If it doesn't ring, it's because the ringer is broken or disconnected or the clapper is restricted.

bigkim100
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pulse/rotary dialing

Post by bigkim100 » Sat Sep 02, 2006 6:28 pm

This may not effect you in your area, but here in Ontario, Canada, a News program uncovered a additional monthly charge, buried within the slew of "standard" monthly charges, for people who kept rotary phones, instead of switching to touch-tone phones. Elderly people who wanted to keep their old pulse/rotary phones were shocked to find out tht buried deep within their bell bill, they were charged an additional $15.00 a month to keep the equipment on their lines that could decode this type of dialing.
Of coarse, most kept their old phones, hoping to save a few bucks on "newfangled" phones... only to find out that they could have bought a new phone every month for what they were being charged to keep their old phones working.
Penny wise...pound foolish. :shock:
Kim..The man with the cute little girls name...and Frankensteins face and body.

KamPutty
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Post by KamPutty » Sat Sep 02, 2006 7:29 pm

stevech wrote:what you have is correct. If it doesn't ring, it's because the ringer is broken or disconnected or the clapper is restricted.
the clapper looks fine...I think the ringer may be the issue...

Whats the best way to check this? Can I just put some volts on the connections and make the magnet work manually and then work backwards...

~Kam (^8*

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Chris Smith
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Post by Chris Smith » Sat Sep 02, 2006 7:45 pm

Your ringer equivalent in your area may reflect modern phones, and thus not contain enough energy to actually run the large cap and bell.

In the old day they had to deliver a whopping charge to ring the old bell, and they also knew how many phones were connected this way, but everything has changed.

Your cap and circuit could be bad, or they just don’t deliver enough charge to set it off?

Try using a absolute ground as well at the phone line, as modern phones tend to float back to the pole, its circuit, and its ground?

You can always hack an old phone on the same line to make sure the line works, and watch the old ringer or chart its effect for a “tryâ€

rshayes
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Post by rshayes » Sat Sep 02, 2006 9:47 pm

The ringer circuit is fairly simple. When the phone is "hung up" or "on hook", the ringer is connected in series with a capacitor across the phone line (the red and green wires). Note that the label on the side identifies these terminals as L1 and L2. Usually the yellow wire is not connected, and in this case is connected to a terminal marked "G", probably meaning ground.

As I understand it, the yellow wire may have been used on party lines, where the ringer could be connected from L1 to L2, from L1 to ground, or from L2 to ground. I suspect that party lines are only used in very rare circumstances these days.

The ringing signal is a burst of 20 Hz AC at around 70 volts. This might be tricky to simulate.

Possible problems, since the phone is old, would be dirty contacts on the switch hook, an open ringer coil, or an open capacitor. The contacts and ringer coils can be checked with an ohmmeter. A rough test for the capacitor can also be done with an ohmmeter. The reading should start low but rise rapidly within a second or so. Most of the ringer circuit should be traceable, since it is separate from the voice circuits, which use a couple of inductors located in those assemblies.

dyarker
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Post by dyarker » Sat Sep 02, 2006 10:23 pm

I had a long reply with explanation almost ready to post and power went out. I'll just do short version in case it goes out again.

With green, red and yellow wires disconnected from line and handset on-hook, measure resistance of green to yellow. If resistance starts relatively low and rapidly climps to open; then connect yellow wire to green and phone should ring. If there is continuity after a couple seconds of the meter being connected, the phone was setup for a party line; connect a capacitor to yellow, other lead of cap to green. Cap should be 250V; mylar, paper or poly. Value probably between 0.1uF to 1uF. I can't tell you the value, but it needs to make a 20Hz resonant circuit with the ringer coil.

For example to find value experimentaly try 0.22uF, then 0.47uF, then 0.22uF parallel with 0.47uF, etc.

In the photo, it looks like a later model 500 (like C or D), so ringer equivelence might be okay. (model number on the bottom)

Bye, (before power goes again)

(while I was waiting for reboot, typing again and getting coffee, rshayes posted; so it looks like I duplicated info. At one time "G" may have meant "ground", but electrical use increased (like 1930s) the hum would have become too great. Correct about party lines and yellow. The internal cap at "A" and "K" wouldn't work (alone) for the different party line ringing frequencies.)

(power still holding, so I went and found the schmatic I had link for the first time around -
http://www.bellsystemmemorial.com/image ... ematic.gif
is for 500C and 500D models.

If any one is curious, the model number for a standard Ma Bell DTMF phone is 2500.)
Dale Y

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jollyrgr
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Long Time Ago

Post by jollyrgr » Sun Sep 03, 2006 6:35 am

In the old days the yellow wire was separate and was part of the ringer circuit. To hide phones from the phone police people would disconnect the ringers, namely the yellow wire. (The phone company used to charge extra for more phones and would scan lines for "ringer equivalents" to see if you were cheating them. Sort of like the modern RIAA looking for music files.)

Look at terminals L1, L2, and G. Follow the wires on L2 (where the red wire connects) going inside the phone; likely one will go to the switch assembly then to the bell coil or possibly directly to the bell coil. On G do the same thing, again this may go to the switch then the bell or directly to the bell coil. If both of these turn out to be true, then disconnect the YELLOW wire entering the phone and tape it off. Use a short jumper and connect L1 and G. Connect the phone line to L1 and L2.

Want to make a SIMPLE tester for the ringer? Get two AC power transformers. Even wall warts will work as long as the output is AC. It would be preferred that one is 12VAC and one is 9VAC but as long as the voltages are close or the same you will be okay. Hang up the phone. Connect the phone to the plug lugs or 120VAC input of the HIGHER voltage transformer. Connect the two lower voltage sides of the two transformers together. Basically you are going to take 120VAC house current, step it down to a lower voltage like 9VAC with the first transformer, then you are going to take the 9VAC and step it back up. If you use a 9VAC and 12VAC you will step 120VAC down to 9VAC then back up to 90VAC, what the phone normally sees. Of course it sees it at 20 to 30 Hz and you are driving it at 60 Hz. But this will be "good enough" for a quick check without making a phone call.


UPDATE: Since I posted the above I explored the site that dyarker linked. I found my answer in picture form. Look at this:

http://www.bellsystemmemorial.com/pdf/5 ... cation.pdf

Says almost exactly what I did only it suggests moving the wire from G directly to L1 instead of using a jumper.
No trees were harmed in the creation of this message. But billions of electrons, photons, and electromagnetic waves were terribly inconvenienced!

KamPutty
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Post by KamPutty » Tue Sep 05, 2006 8:50 am

Thanks all! Moving the wires as suggested worked! yipee!
Now, there is *alot* of static on the hearing side...better look at the connections between the 2 cables...

Thanks again!

~Kam (^8*

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jollyrgr
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Post by jollyrgr » Tue Sep 05, 2006 3:30 pm

The static you hear is likely not a connection problem with any of the wires unless it is happening when you move them. If it sounds like a low hissing sound, similar to air escaping from a balloon, and comes and goes, it is not in the "receive" side of the phone. Instead it is the mouth piece.

Unscrew the mouth piece cover and take out the microphone. It should come out without having to detatch any wires. Lightly rap the microphone on a hard surface several times. Put the mic back in. Problem likely solved.

These are old carbon micrphones and the carbon grains need to be re-arranged.
No trees were harmed in the creation of this message. But billions of electrons, photons, and electromagnetic waves were terribly inconvenienced!

dyarker
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Post by dyarker » Wed Sep 06, 2006 3:58 am

Another possibility (after doing what jollyrgr said) clean the contacts in the hook switch that are closed when off hook. The voice signal also passed through a set of contacts in the dial.

The proper tool is a burnisher, but those are getting hard to find. Get a strip of emory cloth about 1/4" wide and 5 to 6 inches long. Fold in half so that the rough side is inside. That's right, the back of the emory cloth is rough enough to clean the contacts (unless the phone has been soaked in muddy salt water). Another possible cleaning tool is paper matches.

Be very careful not to bend the contact leaves. If you need to go into the dial, be very very careful not to let spring and cam mechanizm fly apart.

The contacts on the carbon mic and in the handset can be cleaned with a pencil eraser.
Dale Y

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frhrwa
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Post by frhrwa » Fri Sep 08, 2006 9:36 pm

L1 & L2 are the Green and Red leads or T & R... the yellow usually went to A or K.. its been a long time and I don't remember, but you can check by moving it from one to the other... A & K are the network capacitor for the ringer coil... one side is already connected to the T side of the line.. so, connecting the Y lead to the right A or K will enable the ringer.... normally

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