How do I wire a GPO pendant telephone, Tele 713?

[andy1702]

I'm looking for any information on how to wire up a GPO 713 pendant telephone. I know it has to be wired to a bellset and a draw dial, but I'm not sure what to connect to what. I've got the pendant phone and the draw dial on their way and I've found some photos of a Bellset 50B, which looks like it's just the chassis of a 746 with some of the components removed. Well I've got plenty of 746 spares, so I think I can make that bit.

The problem is that I'm drawing a total blank for any information on wiring the components up. Even Sam Hallas's website (where we normally go for info) only has pictureds of the components and a description, with no details of how to wire them.

To add an extra bit of a challenge, the 713 I've got coming has a neon light in the handset, so there must be some extra connections to make that flash when a call comes in.

Any ideas anyone?

[Jim Stettler]

I would try to wire it as a 746. From what you are saying, my guess it is the same or close. Once you match the obvious, the rest should be easier to figure out.
Good Luck,
Jim

[twocvbloke]

When in doubt, the N-Diagrams help:

http://www.samhallas.co.uk/repository/n_index/index.php?dir=0000/&file=N813.pdf - 713 wiring diagram
http://www.samhallas.co.uk/repository/n_index/index.php?dir=1000/&file=N1901.pdf - Handset No. 7 (Neon Lamp signalling)

[andy1702]

Thanks for that. I think I can work itout from those diagrams.

[twocvbloke]

No probs, been wanting to get myself a 713 and have the Handset No. 17A (bought from Bob Freshwater (of BritishTelephones.com) himself no less!) so have had those N-diagrams on hand for a while, though the two handsets are different, the neon lamp part is the same wiring...

[FABphones]

I'm looking for any information on how to wire up a GPO 713 pendant telephone. I know it has to be wired to a bellset and a draw dial, but I'm not sure what to connect to what. I've got the pendant phone and the draw dial on their way and I've found some photos of a Bellset 50B, which looks like it's just the chassis of a 746 with some of the components removed. Well I've got plenty of 746 spares, so I think I can make that bit....

Could you pop some photos up Andy, and some showing your progress.

I've got one of these that I've built up from the spares boxes. I connected a handset ok as luckily the extensicord was left on the wall unit. The other three parts I just assumed connected as usual phone wiring; handset to wall unit, that unit to dial, then to a wall bell. Just with longer cords. Sounds like I may need to double check it against your findings. My test gear not set up yet.

[andy1702]

I've picked up the pendant phone today but it's still in the back of my van at the moment. Having studiesd those diagrams and had a read through Bob Freshwater's pages about bellsets, I think the bellset can be constructed from the chassis of a telephone 746.

As an aside to all this... Does anyone know how to access the neon to change the bulb?

I'll make a start when I get a spare minute and let you know how I get on.

[twocvbloke]

Changing the neon should be somewhat unnecessary, unlike ones used in appliances as power indicators, the ones in these handsets seem to last forever so long as they don't lose their seal, as for how, erm, pass, but I assume it would require removing the handset cable and probably extracting the strip it's attached to via either the transmitter cup or through the cable entry itself, I've not tried with my 17A for fear of breaking it... 

[andy1702]

I've made a strange discovery... The neon in the handset on this pendant doesn't actually look like a neon at all. On close inspection it looks like two tiny grain of wheat bulbs.

I had a good look at the diagrams this morning and it looks like I need an 8 way cable between the phone and my home-made bellset 50B. However as I've got a 'neon' and, as it turns out, an on/off switch, I have a horrible feeling I'm going to need a 12 way cable.

The colours in the 8 way seem to reveal it to be a standard 4 pair cable. But what is the 12 way? Does 6 pair cable exist? I've never seen any.

I'm hoping to start work assembling the bits tomorrow, so pictures will follow soon. 

[twocvbloke]

The neon lamp sounds intriguing, I know there's different styles of lamp, but that sounds rather different...

As for the cabling, there are 6-pair cables available as modern stuff, a good example here:
https://www.ebay.co.uk/itm/223033480068
(plenty other listings if you want to shop about, but £6.50 for 10 Metres seems decent enough for the job)

I don't know what the originals were referred to as other than the "Cable 12W" label on the N-diagram...

[FABphones]

Have you got any photos for us yet Andy, it would make it easier to follow if we could see what you can see. 

https://www.britishtelephones.com/t713.htm

[andy1702]

I've been working on the first stage of getting this telephone operational today. The whole thing consists of 3 parts. The pendant telephone, a bellset 50B and a drawer dial. The phone is little more than a handset that sits on a hookswitch in a plastic mounting. The dial is a bog standard dial 21 but mounted in a metal and plastic drawer so it can be mounted onto the underside of a desk and teh dial pulled out for use.

The bit I've started on today is the bellset 50B. It has to be a 50B, not a 50A or 50C because the 50B is the only one with an induction coil built in.

My problem was that I didn't have the bellset 50B, but a bit of research revealed the fact it's based on the chassis of a tele 746. The only difference is and extra terminal, which would equate to T20 in a 746. Now as a 746 only has terminals up to T19 I had to work out what T20 actually did. There followed some comparison between 746 circuit boards and I found some have unused oblong holes in the board which are marked T19A. It turns out T19A does not connect directly to T19 at all, but actually goes to one leg of the hookswitch which doesn't normally have a terminal connection. If T19A had actually been fitted out with a screw terminal I could have used it as T20 (T19A & T20 are one and the same on a 746 board it would seem). If your board doesn't have a space for T19, then you can use one of the solder connections that will be vacated by the hookswitch we are going to remove.

You'll see from the images below that the bottom row of terminals, except for those on the outer ends, don't actually have any tracks that go anywhere. So rather than go to the trouble of fitting out T19A/T20 with a screw terminal, I just soldered a bit of orange wire to the track which went to T19A/T20. The other end of the wire I soldered to T13, which is one of the totally unused terminals on the bottom row (see last photo). The idea is that anything I find that should connect to T20 will now be connected to T13 instead.

I totally removed the hookswitch, which has gone into the parts bin for future re-use. I also removed the dial that was fitted to the chassis. The hookswitch assembly could also be removed, but I didn't have a small dril to hand to remove the rivets, so I left it for now.

[andy1702]

The next stage was to wire the pendant phone to the 746 (which we'll not call the bellset) with an 8 way (4 pair) standard telephone cable. My pendant is fitted with an on off switch for the bell and also a  'neon' in the handset. To make these work I would need a 12 way (6 pair) cable, which I don't have. So both these optional extras were disconnected for now by stacking their fork connectors on a dead terminal in the telephone.

A second 8 way cable is used to connect the bellset to the dial. However only 5 cores are used from this one.

See the photo below for how to connect everything up. Note the jumpers in the bellset, but please also note this is for old fashioned 2 wire working. If you're in the UK and want it to work on the current plug and socket system, then only fit jumpers and a resistor exactly where you would for converting a standard tele 746. This means removing the jumper between T6-T7 and replacing the one between T4-T5 with a 3.3k ohm resistor. Red of the line cord then goes to T8, white to T18 and blue to T6. The bell coils are connected between T4 and T16, again as you would for a standard 746 conversion.

Wire everything up as shown in the diagram and it should work. Mine does! 

[twocvbloke]

It has to be a 50B, not a 50A or 50C because the 50B is the only one with an induction coil built in.

And if you use a high impedance ringer coil, that would make it a 50D...

[andy1702]

And if you use a high impedance ringer coil, that would make it a 50D...

True. I forgot about that one. The coils in my creation are 500ohm each, so I need to add a 3.3k resistor, which I need to remember as I've not done it yet.

What I'm now wondering is if it would be possible to connect my home made bellset to a tele 150? I've been looking for a bellset 25 at a sensible price for over a year without much success. I've picked up quite a few 26s though.