Tracing a circuit of a (modernish) rotary telephone.

Discussion in 'The Projects Forum' started by dezweb52, Feb 22, 2013.

  1. dezweb52

    Thread Starter New Member

    Oct 12, 2011
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    Hi,
    I know this is a long shot and maybe like debugging in the dark but here goes. I have a telephone with a rotary dial, seems to be relatively new so probably a 'relaunch' of a classic (candle stick in this case).

    I recieved it with the mouthpiece, reciever, bell solenoid and dialer wires all connected. However, the phone wire (the bit that plugs into the wall) was missing.

    My question is, is there anyway i can back trace the circuit to find out which pins the wires should go so I could reconnect it? I have tried a few combos on a VOIP box (not going to plug it into the BT network - not yet anyway...) and managed to get a dialtone, but can't seem to hang up the connection.

    I can post a picture of the circuit. I looks fairly easy to trace through - I should be able to get some decent shots if you think it would help.

    Thanks in advance and sorry for the long post / if its in the wrong place.

    Thanks!!!!
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Can you post photos of the face and bottom of the telephone?
     
  3. dezweb52

    Thread Starter New Member

    Oct 12, 2011
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    Yep. Sure. How do I do that? :) every time I try it wants a web link. I'll have a look at the help files and get them posted soon. Hopefully! :)
     
  4. dezweb52

    Thread Starter New Member

    Oct 12, 2011
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    Hi, I have attached the images. Hopefully they are clear. I have marked up what I remember with regards to the wiring. I marked up these before I took it apart.

    Back:
    back.JPG

    Front:
    front.JPG

    Thanks again!
     
  5. Externet

    AAC Fanatic!

    Nov 29, 2005
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  6. dezweb52

    Thread Starter New Member

    Oct 12, 2011
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    Ah. I did have a look there, and had a look about. Unfortunatly, they dont really help me much. I think the lack of understanding on what the wires coming out from the phone socket are and the lack of simple diagrams on how inside a telephone works. The circuit out of the phone is realtively simple, however as I can't find anything online that tells me what pins go where when they enter the phone and a simple diagram on how its wired up inside, I can't make head nor tail of it.

    All help is greatly received though!
     
  7. MrChips

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    Oct 2, 2009
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    Just a thought. Where are you located? Are you sure that rotary phones are still supported?

    Anyway, here is a circuit that might help:

    [​IMG]
     
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  8. dezweb52

    Thread Starter New Member

    Oct 12, 2011
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    Hi MrChips,
    I'm based in the UK so we still have pulse dialing (the last time I tried 'showing off' we did anyway) so the phone should work on the line. I'll have a look at that diagram as see if I can make head or tail of it. The circuit looks easy to trace, but its having the initial knowledge of how it all hangs together before actually understanding the circuit!
     
  9. dezweb52

    Thread Starter New Member

    Oct 12, 2011
    29
    1
    --Edit. Where I have got the wires currently. If I dial in, the 'working' phone rings, but I can here the ringing clicks followed by the caller id information being passed by on the phone that I am trying to get working....Interesting....

    Well, I've wired up the red and green from the phone jack on what I believe to be based on the circuit above. I can hear a faint buzzing and when I open the connection with another phone on the same line I can hear a dial tone. However, I cant seem to get a dial tone nor 'hang up' using the circuit.

    Something funny is going on with how I've wired it, just not sure what. Currently got red on terminal 1 and green on teminal 4. If I put red on terminal 3 I get the dial tone, but not able to hang up.

    I also have black and yellow. Which Im not sure if they are needed to make this circuit work.....
     
    Last edited: Feb 23, 2013
  10. MrChips

    Moderator

    Oct 2, 2009
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    Black and yellow are used for a second line. You don't need to connect these.

    My guess is:
    Red goes to a
    Green goes to b


    If that does not work, presumably the connections at x-y-z and u-v-w are for the handset hook switch.
    Get an ohmmeter and tell me what connections are closed when the handset is on the hook and off the hook.
     
    Last edited: Feb 23, 2013
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  11. dezweb52

    Thread Starter New Member

    Oct 12, 2011
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    Hi MrChips,
    OK. Connecting up where you said to means that when closing down the switch, it silences the receiver. However, toggling the switch doesnt give a ringtone. I can hear the ringtone when lifting another handset on the same line, but not by toggling the switch.

    Pinout from x-y-z and u-v-w are as follows. I have stated what condition the switch is in when the pins are open (as in high resistance). Hope this helps!

    x-y = open when switch open
    x-y = open when switch closed

    u-v = open when switch open
    u-w = open when switch closed

    I also have the cross connections, but will post them if required. I dont want to make things more complicated....haha...

    Thanks for your help so far!
     
  12. MrChips

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    Oct 2, 2009
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    What you have written is not clear.

    Here are my assumptions. Correct me if I am wrong.
    That metal lever with the spring is the hook switch.
    When the handset is placed on the hook a plunger presses down on the lever.
    When the handset is off the hook the spring pulls up the lever.
    This component is a double pole two-way switch with contacts marked as x-y-z for one switch and u-v-w for the other switch.

    I would expect that when the handset is on the hook x-y is closed and u-v is closed.

    When the handset is off the hook y-z is closed and v-w is closed.

    I need you to confirm the last two statements.
     
  13. dezweb52

    Thread Starter New Member

    Oct 12, 2011
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    Hi. What you have said is correct. Re-reading what I have said isn't clear, my apologies! The connections you state is a DPDT switch and the last two statements are correct.

    Fire the questions away. I'll try to answer as best I can!

    Thanks again!
     
  14. MrChips

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    Oct 2, 2009
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    Thanks for the response. Give me some time to think about this.
     
  15. MrChips

    Moderator

    Oct 2, 2009
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    The way the traces on the printed circuit board are laid out makes no sense to me.

    You said you got a dial tone on the receiver. What connections did you make to get the dial tone?

    The only thing I see is:

    connect RED to (a)
    connect GREEN to (b)

    jumper (g) to (1) - this is a wild guess.
     
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  16. MrChips

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    Oct 2, 2009
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    Unrelated question.

    Is there any trace connected to terminals (S3) and (t)?
     
  17. dezweb52

    Thread Starter New Member

    Oct 12, 2011
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    Thanks MrChips. I'll double check the connections when I get home but I think what I said was true. Frustrating that I can't seem to get a dial tone. Might need to give up on it....

    I'm sure your guesses aren't as wild as mine!!
     
  18. MrChips

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    Oct 2, 2009
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    Nah! Don't give up so easily.

    It seems like the board was laid out for other situations and we just haven't figured it out.

    With some experimentation we should be able to get this working.
     
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  19. dsk

    New Member

    Feb 24, 2013
    15
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    Give it a try with line to these 2 terminals.
    The diagram over are probably not right, I m quite sure this one is a wheatstone bridge type circuit. (Widely used in Italy ,germany ++++)

    dsk
     
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  20. dezweb52

    Thread Starter New Member

    Oct 12, 2011
    29
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    Ah. Maybe I should of googled the name on the circuit board earlier...it seems t is fr Italy. Wow dsk! Go you suggest I try it with the connections that MrChips is suggesting? I'm going to look at the switch again and the track connections that he suggested and get back to you guys.

    I'm not quite ready to give up, I'm glad someone is helping though. Was on it a while before asking on here!
     
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