British 700 series phone .

[electric al]

Anyone ? 

How to replace line cord on a British 700 series phone to enable it to be used on our North American system .

[twocvbloke]

It's easy, but I need to know which model it is (706, 746, 711, 741, etc.), just so I can re-acquaint myself with the appropriate N-Diagrams, and if it has a white BT plug on the line cable or if it has a terminal block and/or spade ends...

Also I'd need to know if the ringer is a 1K Ohm (coils will say 500 Ohm on each coil) or 4K Ohm (2000 Ohm on each coil, or 4000 Ohm if it's a Unicoil), as the 1K Ohm will require an additional 3.3K Ohm resistor in line with it...

[dsk]

Identify your phone here: http://tinyurl.com/plqpuve
The resistor in mention are to reduce the REN load, and may be important as soon as you want more than one phone on the line.
dsk

[electric al]

It's easy, but I need to know which model it is (706, 746, 711, 741, etc.), just so I can re-acquaint myself with the appropriate N-Diagrams, and if it has a white BT plug on the line cable or if it has a terminal block and/or spade ends...

Also I'd need to know if the ringer is a 1K Ohm (coils will say 500 Ohm on each coil) or 4K Ohm (2000 Ohm on each coil, or 4000 Ohm if it's a Unicoil), as the 1K Ohm will require an additional 3.3K Ohm resistor in line with it...

  The line cord has 4 wires   Red-Green-Blue -White .

  Coils are 2000 ohms (2)

Model #   8746G  DFM.82/2

  Line cord plug is a BS 6312

[twocvbloke]

A relatively "modern" 746 then built by Denis Ferranti Meters Ltd., in Bangor, North Wales...

Well, no resistor is needed as you have a 4K Ohm ringer assembly, just needs rewiring to work as a 2-wire device...

Simplest way to start is remove the line cable wiring (leave all other wires in place so not to end up in a confused mess) and remove the straps from the PCB, then following the first diagram (Fig. 1) of the N-Diagram number N846 (link below) wire it to the original standard, minus the Green and Blue wires, connect those to T11 and T12 to isolate them.

(PDF File link)

If the phone is missing the capacitor(s) labelled C1 and C2 (usually only C1 is occupied), and being a relatively late phone it's likely, then you would need to fit a metallised film, non-electrolytic capacitor of 1.8uF (could get away with as little as 0.47uF) to C1 (or between T7 and T8 if you don't feel like soldering) as this is required for the ringer to operate.

Once the phone is wired and strapped (you can use pieces of wire as straps if there aren't enough in the phone) as per the diagram, connect a strap between T17 and T18, this completes it's 2-wire configuration.

Now you can either use a UK to RJ11 adaptor available on ebay from various sellers, or, snip off the BT plug and crimp on an RJ11 plug making sure to put the Red and White wires on the middle pair of pins of the RJ11 plug (see pic below), then plug it in and off you go...

Bear in mind that these are simple phones, in this configuration they suffer from "bell tinkle", where dialling another pulse-dial phone on the same line will cause the ringer to strike one of the bells, and your voice will be a lot louder in the receiver than a US-type telephone which can take some getting used to...

[twocvbloke]

An additional help, the wiring should look something like this when you've completed it (note; I used T12 and T13 for the Blue and Green line wires, as the angle of the picture looks as though the handset blue goes to the same terminal, which it does not):

[electric al]

I am trying to post my pictures but for some reason my post will not Post !

[twocvbloke]

The forum's been having a few issues with posting pictures, took me 5 attempts to get the above picture posted, with various attempts at resizing the picture 'til it posted!!!

[electric al]

Thanks for your help!

I found the problem , the fingerwheel was not travelling back the full distance !

Working fine now !

Thanks to all that helped me solve the problem.

[twocvbloke]

That's good to hear, I guess the next step is to refurbish and lubricate the dial so it returns properly...