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Gpo746l telephone ringing issues in spain

Started by Applemac, October 27, 2015, 07:36:13 PM

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Applemac

Hi,

Im hoping someone could possibly help me, I have a gpo746L which has been converted however it does not ring on incoming calls, I bought the phone in the UK however I live in Spain, the telephone system here has a ring current of 75 volts ac on 50hz. Is there another ajustment I need to do in order to have this phone ring when called. All other functions work I can ring out, and hear the other person perfectly.

Thanks in advance for any help.

Jack Ryan

Hi,

What do you mean by "converted"? In the UK "converted" usually means rewire for "plug & socket" and add a resistor.

Attached is the circuit of a "converted" 746. This should not work at all in Spain unless you use the same Plug & Socket arrangement. Perhaps yours just has a 3k3 resistor added in series with the bell.

Aside from that issue, 50Hz is a bit quick for a 746 bell. Is the bell *trying* to ring? Is it vibrating?

You might be able to get it to ring by adjusting the bell gongs so they are closer to the clapper. The mounting hole in the gong is off-centre to facilitate this. If the ubiquitous 3k3 resistor is present, you might try replacing it with a wire link. Ringing the bell at 50Hz is hard enough without the resistor.

Jack


Applemac

Hi, i mean its been converted to be used in the uk with the 3k3 resistor and the diode.. It has a standard uk plug attached which I bought a rj11 to rj45 convertor to plug into the wall.

The bell is not trying to ring at all.. When receiving an incoming call I checked to see if there was any movement with the bell gong and no vibration at all.

twocvbloke

If the phone still has the C1 &C2 capacitors (sometimes just one 1.8uF capacitor on C1), then remove the Blue wire & place it on one of the spare terminals, then connect a strap or a piece of wire between terminals T6 and T7, this should get it to ring...

Bear in mind though that you may suffer with "Bell tinkle" if there are other pulse-dial telephones on the line, and when other phones are picked up and hung up... :)

Applemac

Okay all thanks for the information I will try it later today and report back.

I really appreciate the help.

Jack Ryan

I have no idea how the phone is connect to the line (what does the adaptor do?) and I am only assuming that the circuit I made earlier matches the phone.

If the circuit matches the phone, I would link T7 and T6 and connect tip and ring to "R" and "W". Assuming that the capacitors C1 and C2 are present the bell should *try* to ring. If needed, I would further add a link across the resistor between T4 and T5.

What troubles me is that if the circuit is correct, how did the phone work without the bell line connected? It is not just a bell connection; it is part of the receiver circuit.

Jack

twocvbloke

The circuit works as the hookswitch contacts shunt the ringing voltage across the ringer when on-hook, and when the receiver is lifted the equipment in the exchange detects the change and stops ringing & connects the call... :)

As for the "How it's wired", it's simple, the standard UK telephone wire colours are Red, Blue, White and Green, Green is generally not used (it was mainly for Earth-loop recall functions on shared service and PABX systems), the Red and White are the Green and Red in US wiring, the Blue bell wire carries the ringing current from the master socket which contains a ringing capacitor and a test resistor (gives a 1/2 REN reading I believe for the BT-Openreach people to read when checking to see if a line is connected or not)...

Adaptors for UK to RJ11 tend to be two-wire, so miss out the Bell wire, therefore results in no ringing, it's similar to how on a WE500 you have to move one of the ringer wires over to get it to ring, except in a GPO 706 and 746 type phone and their variants, you just alter the straps to accommodate the wiring needed... :)

Jack Ryan

Quote from: twocvbloke on October 28, 2015, 06:30:58 AM
The circuit works as the hookswitch contacts shunt the ringing voltage across the ringer when on-hook, and when the receiver is lifted the equipment in the exchange detects the change and stops ringing & connects the call... :)
Right.

Quote
As for the "How it's wired", it's simple, the standard UK telephone wire colours are Red, Blue, White and Green, Green is generally not used (it was mainly for Earth-loop recall functions on shared service and PABX systems), the Red and White are the Green and Red in US wiring,
Do you *know* this is what we have here or do you *guess* this is what we have here? Guess means "don't know".

Quote
the Blue bell wire carries the ringing current from the master socket which contains a ringing capacitor and a test resistor (gives a 1/2 REN reading I believe for the BT-Openreach people to read when checking to see if a line is connected or not)...
That wire also carries the receiver current. The capacitor has a dual function; it is the ringing capacitor and the AC coupling for the receiver (it replaces the C1 + C2 pair in the telephone).

Quote
Adaptors for UK to RJ11 tend to be two-wire, so miss out the Bell wire, therefore results in no ringing,
And a receiver that is not coupled properly.

My comments were meant to express the fact that without seeing the telephone in question I am making a lot of guesses as to (1) how the phone is connected and (2) what might be going wrong.

Regards
Jack

Applemac

Jack not sure what you mean by tip and ring to r and w...

dsk

My suggestions are on this diagram:
dsk

twocvbloke

Quote from: Jack Ryan on October 28, 2015, 07:16:45 AMDo you *know* this is what we have here or do you *guess* this is what we have here? Guess means "don't know".

100% Positive, converted GPO telephones have such wiring, there are kits on the web to convert hard-wired GPO phones which use the standard British Telecom wiring code of Red, Blue, Green, White, and the wiring performed to convert the phones is a single standard...

The only thing I'm not sure on is why I'm being questioned about it in such a manner when I've converted, de-converted and part-converted many of my own GPO 706 and 746 telephones... ???

Quote
That wire also carries the receiver current. The capacitor has a dual function; it is the ringing capacitor and the AC coupling for the receiver (it replaces the C1 + C2 pair in the telephone).

No, the blue Bell wire is solely used for the ringing current, when the bell is disconnected, the signal path, between the Red and White wired of the line, runs elsewhere, and if you look on the two provided diagrams, you'll see that C3 is the AC coupling...

Quote
And a receiver that is not coupled properly.

See diagrams...

QuoteMy comments were meant to express the fact that without seeing the telephone in question I am making a lot of guesses as to (1) how the phone is connected and (2) what might be going wrong.

My comments are based on experience and many hours studying the N-Diagrams (the GPO equivalent of BSPs) on these phones, aswell as putting the knowledge into practice on my collection of GPO and derivative (such as my MOD versions and my "Storno" version) phones, so I'm not guessing here, I know what's going on as the phone is a three-wire setup and the BT to RJ11 adaptors are 2-wire resulting in no ringing, and the solution is as I have posted... :)

Jack Ryan

Quote from: Applemac on October 28, 2015, 12:23:54 PM
Jack not sure what you mean by tip and ring to r and w...

I mean the line (telephone) wires from the exchange - also called L1 & L2 or A and B.

Jack


Jack Ryan

Quote from: Applemac on October 28, 2015, 12:23:54 PM
100% Positive, converted GPO telephones have such wiring, there are kits on the web to convert hard-wired GPO phones which use the standard British Telecom wiring code of

OK but you are assuming that everyone else does exactly the same thing. If that were the case there would be very few wiring problems.

C3 is part of the line balancing network. C1 + C2 is a signal path.

But - each to their own.

Regards
Jack

twocvbloke

Not wanting to start an argument, but, GPO Telephones are something I know about a dn the standards used, even when posted to another country, are the same regardless of whether someone else disagrees...

Applemac

#14

I have made an error this is not a 746 this is an gpo706L im so sorry for my stupid mistake.


Thats the last thing I want is an argument happening, this is my first telephone so need as much help as possible, the rj11 to rj45 does only have two wire going into the plug that plugs into the wall socket. Theyre red and green.

What I need is someone to explain to me in laymens terms what to do to the phone in order to have it working properly in Spain, which is a 75volt 50hz system.

Please in laymens terms.