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Author Topic: Converting old phone to PST?  (Read 8323 times)

BritBrat

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Converting old phone to PST?
« on: November 06, 2009, 05:47:33 PM »

Anyone have any knowledge on how to do it?

I have an old wall mounted phone I have fitted a BT socket to it and it does phone out and rings/receive calls but I am not to happy about leaving it on the BT network as it may need a few more modifications that I do not know about.

I will put a wiring diagram up shortly and picture of phone (camera batteries gone flat).

Thanks.

BB

Wiring diagram:
http://img687.imageshack.us/img687/1032/img0283g.jpg

Inside view:
http://img94.imageshack.us/img94/9193/img0275j.jpg

External view:
http://img689.imageshack.us/img689/9800/img0288v.jpg

Looks like it was made by Automatic Telephone & Electrical Co. - Liverpool (later Plessey)
« Last Edit: November 07, 2009, 12:56:34 PM by BritBrat »
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kitz

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Re: Converting old phone to PST?
« Reply #1 on: November 07, 2009, 12:29:28 PM »

I dont Im afraid,

but does this help?

http://www.britishtelephones.com/pstconv1.htm
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BritBrat

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Re: Converting old phone to PST?
« Reply #2 on: November 07, 2009, 12:53:34 PM »

Thanks for the reply but I have already looked at that, the thing is I am not sure what one relates to the phone I have.


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Tim69

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Re: Converting old phone to PST?
« Reply #3 on: November 13, 2009, 12:23:20 PM »

In essence the conversion of all old phones is the same.
   
  (1) Check the impedance of the bell. Its likely to be 1k ohm, so add a resistor in series with it to bring it up to 4k ohm ( this is not too critical, a 3 or 3.5k 1/2 watt would be fine)
 
   (2) You need to disconnect the phone ring cap ( marked 2 on the diagram) at terminal 3  but leave the connection to the bell and the rest of the phone in place.
 
    (3)  connect your lead to the phone so that the bell is connected across the out of service resistor in the master socket, and the ring cap in the master replaces the ring cap in the phone.
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BritBrat

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Re: Converting old phone to PST?
« Reply #4 on: November 13, 2009, 02:04:03 PM »

Thanks very much for the reply.


 (1) Check the impedance of the bell. Its likely to be 1k ohm, so add a resistor in series with it to bring it up to 4k ohm ( this is not too critical, a 3 or 3.5k 1/2 watt would be fine)

Yes it seems to be 1k if I remove strap between 1 - 3 (wiring diagram) and fit the 3.5k resistor in its place will that be OK?



  (2) You need to disconnect the phone ring cap ( marked 2 on the diagram) at terminal 3  but leave the connection to the bell and the rest of the phone in place.

Blue wire I hope as I have cut it off :)



   (3)  connect your lead to the phone so that the bell is connected across the out of service resistor in the master socket, and the ring cap in the master replaces the ring cap in the phone.

Not to sure what you mean here, if I have BT plug connections 2(Green) and 5(Red) connected to 1(A) and 4(B) on phone is the right?
I was only going to use two wires, i.e. no ring ((3) Disconnected at master socket) wire connected  and use a ADSL filter to provide the ring function.
I could have ring wire (3) from ADSL filter connected to (3) connection in phone.

Could you explain why you have to have the higher impedance and the capicitor disconected, I work better when I know why something has to be the way it is.
« Last Edit: November 13, 2009, 04:07:51 PM by BritBrat »
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Tim69

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Re: Converting old phone to PST?
« Reply #5 on: November 13, 2009, 04:07:51 PM »

Yes sorry I should have been  more explicit.   
 
  (1) Yes the resistor would be fine replacing the extension bell link  More on that later.
 
   (2) I should have said it is necessary to use a three way wire with a bt plug on one end ( you can get 4 way ones easily)   
   
       Depending on the colours of the wire, you connect the ring line to terminal 3 on the phone (cutting the  blue wire from the internal capacitor is fine)
     
       The wire which connects to 5 on a normal bt socket connects to A 
       
       The wire which connects to 2 on a normal BT socket connects to B
 
          The reason the bell impedance has to be increased is because these days they are connected in parallel across the line, when your phone was made and extensions were fitted by post office telephones, the bells were connected in series (thats why there is a link for an extension bell). The min impedance for bells across a line is 1K (this is where the idea of using a max of 4 phones on a line comes from 4x4k in parallel = 1k) 
   
        Removing the bell cap (it is also, or was also used for spark suppression at the dial contacts but that is not a problem now) allows just one capacitor on a line 
 I know you wish to use this phone with ADSL filter and it will be fine But do check that there have been no mods carried out on the phone, check against the diagramm
 
   
  Tim
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BritBrat

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Re: Converting old phone to PST?
« Reply #6 on: November 13, 2009, 04:13:52 PM »

Thanks again,

So if I have three wires from BT socket/filter connected to (1)A, (4)B and (3) on phone but (3) ring not connected at master socket would it still ring?

Phone has never had anything done to it, I have had it years and years and always meant to see if I could get it working correctly.

It did work as it is the other day but I did not wan't to leave it standard as I did not know what effect it may have on the BT system.
« Last Edit: November 13, 2009, 04:23:05 PM by BritBrat »
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Tim69

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Re: Converting old phone to PST?
« Reply #7 on: November 13, 2009, 04:20:33 PM »

Yes it will be fine as you wish to use an ADSL filter, which Im sure you know will provide the ring line for your phone. I suppose you have disconnected the ring line at the master to improve your BB performance? 
 
    You may find that the bell sounds is changed with the resistor, you can adjust this by rotating the gongs to move them closer ofr further away from the bell hammer. (this used to be a favorite job for apprentices when extensions were fitted  to a line, happy days :))
« Last Edit: November 13, 2009, 04:26:10 PM by Tim69 »
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BritBrat

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Re: Converting old phone to PST?
« Reply #8 on: November 13, 2009, 04:24:16 PM »

OK, think I have it now :)

Just need to get the resistor and when done I will report back.

Now I have to go find the URL I had the other day on how to polish these phones up to make them look good, it is not to bad anyway at the moment.
« Last Edit: November 13, 2009, 04:30:30 PM by BritBrat »
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BritBrat

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Re: Converting old phone to PST?
« Reply #9 on: November 19, 2009, 05:40:22 PM »

Fitted 3k resistor and new BT plug and cable and it is working :)

Thanks, Tim could not have done it without you.

The most amazing part it it dials out as well, LOL

It feel strange pushing that dial around instead of pressing buttons.

BB
« Last Edit: November 19, 2009, 05:43:29 PM by BritBrat »
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camallison

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Re: Converting old phone to PST?
« Reply #10 on: November 19, 2009, 07:57:37 PM »

Polishing up old phone = Brasso, if it is bakelite, but rub gently
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Tim69

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Re: Converting old phone to PST?
« Reply #11 on: November 20, 2009, 09:37:33 AM »

Jolly good :)   Perspex polish also works well so long as any scratches are not too deep.
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camallison

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Re: Converting old phone to PST?
« Reply #12 on: November 20, 2009, 11:52:32 AM »

 :)  Perspex polish = Brasso, without the colorant and, of course the name.   ;)
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Ezzer

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Re: Converting old phone to PST?
« Reply #13 on: November 23, 2009, 12:36:40 PM »

lots of sign shops or boat chandlers may have acryllic polishes. the come in 3 grades you'll would probably need the medium-corse, works well on acryllic baths. Managed to remove numerous ciggarette burns and defomations from a bath (not mine,i don't smoke)
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