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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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29th Jun 2021, 2:15 pm | #1 |
Tetrode
Join Date: Sep 2015
Location: Margate, Kent, UK.
Posts: 56
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Clunking sound on Type 12 dial when dialling out.
Hello
I have a problem with a couple of dials when dialling out. It is two different dials, a No 10 and a No 12. They dial out and connect fine, but when the dial returns I am getting a clunk when it comes to rest which isn't pleasant on the ear. It is very frustrating as have spent some time getting the phones into working order. From looking at some previous posts it would appear to be a problem with the points. I have cleaned the points but the problem continues. I have also tried them on different phones. Does anyone know what could be causing this and whether there is a remedy Thanks for reading |
30th Jun 2021, 3:59 pm | #2 |
Nonode
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 2,181
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Re: Clunking sound on Type 12 dial when dialling out.
John, going back a loooong time to my days at GPO /PO training schools, I seem to remember that there was a pair of contacts on the dial designed to S/C the receiver on dialling out and these should break when the dial has returned to normal preventing "clacks" in the ear.
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30th Jun 2021, 8:49 pm | #3 |
Heptode
Join Date: Jan 2008
Location: Hakadal, Norway
Posts: 640
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Re: Clunking sound on Type 12 dial when dialling out.
2 diodes in opposite direction shunting the receiver may also help.
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3rd Jul 2021, 2:05 pm | #4 |
Tetrode
Join Date: Sep 2015
Location: Margate, Kent, UK.
Posts: 56
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Re: Clunking sound on Type 12 dial when dialling out.
thanks for reply
So could anyone give me an indication of which set of points this is, and what is the normal resting position(closed or open0 to prevent this clunk when the dial returns. Also with regard to the pair of diodes for shunting the receiver, what type of diodes and where should they be located Many thanks for reading |
3rd Jul 2021, 6:50 pm | #5 |
Heptode
Join Date: Jan 2008
Location: Hakadal, Norway
Posts: 640
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Re: Clunking sound on Type 12 dial when dialling out.
The diodes could be almost any rectifier diodes, and could be put on the receiver terminals in the handset, or on the terminals for the handset cord in the phone. They will short out all peaks of approx 0.7V.
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4th Jul 2021, 3:58 pm | #6 |
Nonode
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 2,181
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Re: Clunking sound on Type 12 dial when dialling out.
JON- have a look at https://www.bing.com/search?pc=COSP&...q=N%20DIAGRAMS
(N diagrams for PO telephones always gave the diagram now a 100 more than the phone. I've looked at a diagram for a 706 phone, where the diagram was 806). Is it a physical clunk or more one in the ear. Physical clunk suggest a mechanical problem. Bang in ear suggests electronical problem. |
4th Jul 2021, 8:24 pm | #7 |
Tetrode
Join Date: Sep 2015
Location: Margate, Kent, UK.
Posts: 56
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Re: Clunking sound on Type 12 dial when dialling out.
Hello
Thanks for the answers For the diodes I do have some here which I can try Should it be one diode for each terminal (three) or are they put across the terminals, in which case what order should they be put in? I think it is definitely an electronic problem. It seems to be one set of points. So not the point that controls the pulses. One of the ones on the other side (the inner one) if you flick it when the phone is plugged in you can almost reproduce the sound, which isn't pleasant on the ear. |
5th Jul 2021, 8:28 am | #8 | ||
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: Clunking sound on Type 12 dial when dialling out.
Quote:
Quote:
Try running a strip of paper between the contacts a few times, while holding them closed, to remove any deposits. Don't use anything more abrasive than that or it may remove the plating from the terminals.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) Last edited by Dave Moll; 5th Jul 2021 at 8:33 am. Reason: addition |
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8th Jul 2021, 6:35 pm | #9 |
Tetrode
Join Date: Sep 2015
Location: Margate, Kent, UK.
Posts: 56
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Re: Clunking sound on Type 12 dial when dialling out.
thanks for reply
Which two receiver terminals is it. There are three wires going from the handset to the main phone. |
8th Jul 2021, 8:50 pm | #10 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: Clunking sound on Type 12 dial when dialling out.
Assuming the handset cord follows the standard colour convention, the receiver is green and the common return is red, so the "rectifier" goes between green and red. The white wire is the transmitter.
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