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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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4th Sep 2021, 6:44 pm | #1 |
Pentode
Join Date: Feb 2019
Location: Worcester, Worcestershire, UK.
Posts: 183
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Old telephone, impulse buy, not working.
Hi all, a bit of a change from my usual lurking place of the old TV section.
So me and offspring1 found ourselves with a bit of free time today, so wondered across to the museum over the road that houses, amongst other things, a collection of old telephone kiosks, and some exchanges. I got chatting to one of the volunteers who looks after the exchanges and he informed me they had some old phones for sale to try to raise funds. So I handed over 10 of my finest pounds and came away with the beauty in the pictures. I assume it is either a 746 or 1307 as these two numbers are stamped on the base. It had been fitted with a modern lead with plug on the end, but I was told it “probably would not work as had not been properly updated”. I could have chosen a different set which had been updated and he said definitely would work, but this was twice the price and I like a challenge. On returning home, I plugged it into the master socket and it does not work. It will ring when I ring the number, but does not dial out (our exchange does support LD dialing) and there is not dial tone on lifting the receiver, only very front clicks can be heard. Can anybody point me to a source of information that will help me wire the thing correctly. I have (hopefully) attached a photo of the wiring as it stands, oddly most of the wires coming from the dial assemble are not connected, is this normal? Thanks. |
4th Sep 2021, 7:01 pm | #2 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,127
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Re: Old telephone, impulse buy, not working.
The red line cord wire needs to go to T8 rather than T9 (which is one end of the internal capacitor (see diagram N846 for details).
You also need the blue wire to T6 and to remove the strap between T6 and T7. Depending on what else is connected to the line, you may also need to replace the strap between T4 and T5 with a 3.3K resistor, but that's a later refinement once the 'phone is working. The green wire is not used and should be parked on a spare terminal, such as the one previously holding the blue wire.
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4th Sep 2021, 7:08 pm | #3 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Old telephone, impulse buy, not working.
It's a 746. You'll find full details of the required wiring on this page:
https://www.britishtelephones.com/pstconv1.htm Alan |
4th Sep 2021, 7:41 pm | #4 |
Pentode
Join Date: Feb 2019
Location: Worcester, Worcestershire, UK.
Posts: 183
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Re: Old telephone, impulse buy, not working.
Thanks both.
Following the links and having a bit of a read, I now have it wired correctly (I think, proof is in the testing I guess). However, I do not have any 3K3 resistors in stock. How accurate does this value need to be? I have 2K7 and 3K9 in stock, or if this is not close enough can make something up with 2 or more in series. Is it better to be low, high, or should I make it spot on? Thanks again. |
4th Sep 2021, 8:03 pm | #5 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,127
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Re: Old telephone, impulse buy, not working.
I don't think the value is too critical. If 3.9K drops the voltage too much for the bell to ring properly, use the 2.7K.
As I say, though, it will work with the strap rather than a resistor. The resistor is simply to prevent this from hogging too much of the ringing current for any parallel telephones to ring properly.
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4th Sep 2021, 8:04 pm | #6 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Old telephone, impulse buy, not working.
Either will probably be fine. I've successfully used 2k7 in the past.
Alan |
4th Sep 2021, 8:36 pm | #7 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 13,998
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Re: Old telephone, impulse buy, not working.
For testing, plug it direct into the BT master-socket, _not_ via an ADSL microfilter.
Not all microfilters pass the 'ring capacitor line' feed through to their phone-sockets. Most phones for the last 40-odd years have been 2-wire and don't need the third-wire ring-capacitor-feed so many ADSL microfilters don't provide it. |
4th Sep 2021, 9:09 pm | #8 |
Pentode
Join Date: Feb 2019
Location: Worcester, Worcestershire, UK.
Posts: 183
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Re: Old telephone, impulse buy, not working.
Thanks all.
The phone is now fully functional. We use VDSL internet so no filters to worry about. I opted for the 3K9 resistor, purely because it was the first of the two packets I picked up. I think it may be a little on the high side as it has resulted in what I would describe as a ‘soft and gentle’ ring. But I think I am going to leave it as it is loud enough and I quite like it a little subdued. It is now in bits again as I have the plastic bits soaking in a mild soap solution to remove the 50 or so years of dirt. |
4th Sep 2021, 9:16 pm | #9 |
Pentode
Join Date: Feb 2019
Location: Worcester, Worcestershire, UK.
Posts: 183
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Re: Old telephone, impulse buy, not working.
Next job is to try and recreate the paper disc for the centre of the dial.
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4th Sep 2021, 10:11 pm | #10 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Old telephone, impulse buy, not working.
Here's a quick way of generating a label in keeping with the period:
http://going-digital.github.io/telephone-dial/ Alan |
5th Sep 2021, 6:24 am | #11 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,208
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Re: Old telephone, impulse buy, not working.
You might want to get the appropriate N diagrams from Sam Hallas's site. These are essentially the circuit diagrams for the telephone
N846 covers the original Telephone 746. N8846 covers the official plug-in version with a 4k Ohm bell. The 746 has a 1k bell, adding the series resistor (which was never 'official' on this telephone although it was on some others) effectively increases the resistance. |
5th Sep 2021, 1:17 pm | #12 | |
Nonode
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 2,181
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Re: Old telephone, impulse buy, not working.
Quote:
http://www.samhallas.co.uk/repositor.../0000/N846.pdf ETA- for the beginner, GPO added 100 to the diagram number for the phone. So a tele 746 will use diagram N846 /a Tele 706b will use N806 and a 332 will use N432. Hopefully that will be of some use to someone. I can't remember why. Most possibly lost in the transition from Plans( 1/1a/5 etc) to how 60 circuits gets fed down a submarine cable or how 960 get shoved from town to town on a coax cable . Last edited by Oldcodger; 5th Sep 2021 at 1:25 pm. |
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6th Sep 2021, 9:31 am | #13 |
Pentode
Join Date: Feb 2019
Location: Worcester, Worcestershire, UK.
Posts: 183
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Re: Old telephone, impulse buy, not working.
Thanks Alan. Little disc made and installed.
All back together again now and nice and clean. Thank you all for the help. |
6th Sep 2021, 11:25 am | #14 | |
Octode
Join Date: Jul 2009
Location: Carmel, Llannerchymedd, Anglesey, UK.
Posts: 1,507
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Re: Old telephone, impulse buy, not working.
Quote:
I have a General Telphones unit in the shack which dates from the 80's -it was left over from a project. They were in Osnaburgh St. An excellent phone with particularly good receive audio - something which benefits my ancient hearing! |
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6th Sep 2021, 5:35 pm | #15 | |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Old telephone, impulse buy, not working.
Quote:
Alan |
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6th Sep 2021, 6:45 pm | #16 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,127
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Re: Old telephone, impulse buy, not working.
I would go along with that. Between Bob's site and the N diagrams on Sam Hallas' site they are invaluable.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |