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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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2nd Apr 2020, 3:02 pm | #1 |
Diode
Join Date: Apr 2020
Location: Coventry, Warwickshire, UK.
Posts: 6
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GPO 8746 Telephone Bell
Hi,
I've just bought a GPO 8746 telephone. Its a nice looking old thing and seems to be mostly working fine. Only issue is when I dial in the bell doesn't ring. If I pick up the receiver when dialling in it does answer. I opened the case and found a loose blue wire from the coil(?). I'm guessing this is my problem. Where should it be connected to? |
2nd Apr 2020, 4:04 pm | #2 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,642
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Re: GPO 8746 Telephone Bell
T4 or T16, whichever is not connected: http://www.thechipmunk.net/phones/8746e.htm
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2nd Apr 2020, 4:13 pm | #3 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,222
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Re: GPO 8746 Telephone Bell
The bell coils say 500 Ohms on them (on each of them), making this a 1k bell. That means that the telephone is probably not an 8746 (which normally has a 4k bell, 2 off 2000 ohm coils) but a 746 that has been converted to the new wiring.
The workaround is to put 3300ohm (3.3kOhm, 3k3) resistor in series with the bell coils. The easiest way to do that is to remove the metal strap (link) between terminals T4 and T5, then connect the resistor between those. As Bill says the wires from the bell coils go to T4 and T16 (T16 is strapped to T17, T18 and T19). Diagrams N846 and N8846 apply to the Telephone 746 and Telephone 8746, you can get them from Sam Hallas's website. |
2nd Apr 2020, 4:26 pm | #4 | |
Dekatron
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,687
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Re: GPO 8746 Telephone Bell
Quote:
If it was an 8746C, however, then yes: it would have the 2K bell coils fitted. Or so I was told when I asked exactly the same question about my 8746!
__________________
Regds, Russell W. B. G4YLI. |
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2nd Apr 2020, 5:05 pm | #5 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,222
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Re: GPO 8746 Telephone Bell
That is why I said 'probably not an 8746'. The common 8746 has a 4K bell, it's what you generally need for domestic installations. The older 746 (hardwired, not plug-in) has a 1k bell.
I've seen reference to the 1k bell 8746 in diagram N8846, but where was it used? |
2nd Apr 2020, 6:23 pm | #6 | |
Dekatron
Join Date: Jul 2007
Location: Penrith, Cumbria, UK.
Posts: 3,687
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Re: GPO 8746 Telephone Bell
Quote:
Think that would be the main difference: DEL would have a 4k ringer; PABX extension a 1K one.
__________________
Regds, Russell W. B. G4YLI. |
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2nd Apr 2020, 7:09 pm | #7 |
Octode
Join Date: Mar 2011
Location: Sheffield, South Yorkshire, UK.
Posts: 1,453
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Re: GPO 8746 Telephone Bell
To simply answer the OP's question:—
A photo showing the entire circuit board would help but it looks like the loose wire should be connected to one of the three screw terminals joined together. Undo one and put the loose wire under it. Odds are it will then work in practise whatever the theory says. |
2nd Apr 2020, 7:58 pm | #8 |
Octode
Join Date: Mar 2011
Location: Sheffield, South Yorkshire, UK.
Posts: 1,453
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Re: GPO 8746 Telephone Bell
I couldn't add this diagram earlier as I wasn't at my main computer. Don't worry about the resistor at this stage. If it works with the strap in place and all your other 'phones still ring there's no need to bother.
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2nd Apr 2020, 8:20 pm | #9 | |
Diode
Join Date: Apr 2020
Location: Coventry, Warwickshire, UK.
Posts: 6
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Re: GPO 8746 Telephone Bell
Quote:
I only have the one landline phone (this one now) so I don't think I'll need the resister. I checked my broadband speed before and after and it was exactly the same so I am assuming its all good? |
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2nd Apr 2020, 9:50 pm | #10 |
Octode
Join Date: Mar 2011
Location: Sheffield, South Yorkshire, UK.
Posts: 1,453
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Re: GPO 8746 Telephone Bell
Sounds like it.
Glad it helped. |