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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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28th May 2012, 3:23 pm | #1 |
Dekatron
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Location: East Yorkshire, UK.
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Direct Line red phone
I have just bought this phone complete with wheels (sad or what?) The bell will not work. The bell coil measures 6.25k is this correct? it moves a ball bearing between two bells.
John. |
28th May 2012, 3:53 pm | #2 |
Octode
Join Date: Sep 2009
Location: Bath, Somerset, UK.
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Re: Direct line red phone
I'd check the wiring at the back - I'm guessing this is a model 746?
there is a great site for these phones http://www.britishtelephones.com/ SEAN
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28th May 2012, 4:06 pm | #3 |
Dekatron
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Location: Oxford, UK.
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Re: Direct line red phone
I think this is a Chinese (or similar) modern phone, cosmetically based on the pushbutton variants of the GPO 700-series phones, but nothing like them inside.
Your DC resistance figure sounds reasonable. Is there any AC voltage being developed across it when the phone is rung? Nick. |
28th May 2012, 4:15 pm | #4 |
Retired Dormant Member
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Re: Direct line red phone
They're Geemarc, I've got one. Internally they bear no resemblance whatsoever to the 746. There's a fairly obscure bell on/off switch underneath; check it's actually switched on and/or functioning properly.
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28th May 2012, 4:41 pm | #5 |
Dekatron
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Re: Direct line red phone
That sounds a bit high, but not completely out of range.
So, next test: Connect phone, opened up, to line (be careful). Ensure hook switch is depressed. Apply probes of multimeter, set to 200V AC range, across bell coil ends (don't hold them on with your bare hands!) Call line from mobile. Check meter -- are you seeing a voltage? The reading on the meter will change in time with the ring-ring, pause, ring-ring, pause; the voltage should be somewhere between 50V and 100V in the rings and nil during the breaks. For the timing, listen to an extension phone on the same line, not the ringing-out tone in the calling handset -- this is no longer certain to be in time with the called phone's bell, as it used to be with the old-fashioned, clicky-clicky exchanges. It is easiest to see what is happening with a mechanical meter, but a digital meter is still better than nothing. What is the maximum voltage reading you get during a burst of ringing? Do you have broadband Internet via your telephone line? If so, are you using filters on each socket, or a whole-house filter?
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28th May 2012, 7:01 pm | #6 |
Dekatron
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Re: Direct line red phone
I couldn't say whether it's correct, but it's pretty much spot on compared with mine (6.23kΩ) - which does ring. I get a voltage reading across the bells of 68V during the ring - using my internal exchange.
Yes, sadly I felt the need to add one to my collection as well. Incidentally, at the risk of sounding pedantic, as it's a twelve-button 'phone, it's pretending to be a 782 rather than 746.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) Last edited by Dave Moll; 28th May 2012 at 7:03 pm. Reason: qualify voltage reading |
28th May 2012, 8:21 pm | #7 |
Dekatron
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Re: Direct line red phone
Thank you for all your replies and Dave for going to the trouble of measuring his coil. I did clean the bell switch but there is no voltage across bell coil when ringing, there is another phone plugged into the same socket and it works ok. Our internet is not now connected to any landline and all filters have been removed years ago. I have checked for continuity in the Line In all three test OK. The caps test OK for ESR. Hook swich test OK for continuity. It would be nice to have a circuit for it, are they available?
John. |
28th May 2012, 8:45 pm | #8 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
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Re: Direct line red phone
Move the voltmeter probes to pins 3 and 5 of the socket (you will have to remove the faceplate from the wall box), and ring the line. Do you get the ringing voltage there? If not then you have a problem with your wiring. Not all phones need pin 3 connected (it comes from pin 2 via a 1.8 μF capacitor; some phones have a capacitor internally, because not every country's phone wiring has a separate ringing wire).
If you get volts on the socket but not the bell coils, test for continuity from the plug to the bell coils. If the phone transmits and receives speech, it must be the pin 3 wire. If you cannot talk to or from the phone, then it must be the pin 5 wire.
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If I have seen further than others, it is because I was standing on a pile of failed experiments. |
28th May 2012, 10:06 pm | #9 |
Dekatron
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Re: Direct Line red phone
I seem to remember disconnecting a wire, orange? in the line box when we were on dial up. Could this "new" phone need the wire even though all the other phones work ok. When I asked the chap I bought it off if it worked he said he rang his friend but he was out? so tried 1471 and it worked, suggesting it may have been faulty at his house. I will check the wire tomorrow. Another thought, there are only three wires going into the phone.
John. |
28th May 2012, 10:30 pm | #10 |
Octode
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Location: Saltburn-East, Cleveland, UK.
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Re: Direct line red phone
Hi,
The above comment suggests that your service provider may be Virgin, which also means that the parameters for your telephone line are slightly different to those on a BT line. The equipment in the street cabinet (mulitplexer) might not like the higher resistance bell coils that your phone has, that said you mention that there is no voltage across the bell coils on an incoming call which in turn suggests a wiring fault either within the phone itself or between the line/linebox and/or wiring. Do you have any extension phones connected when checking your Direct line phone? as a combination of tone callers and inductive callers could be acting as a notch filter at ringing frequency and stealing the ringing current. Try connecting you telephone direct to the test socket behind the NTP front cover (presuming that an NTE5 is fitted) Regards Andrew |
28th May 2012, 10:47 pm | #11 | |
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Re: Direct Line red phone
Quote:
Alternatively, if having the "ringing wire" connected causes problems elsewhere, simply use a plug-in ADSL filter to supply the ringing current through its internal capacitor.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) Last edited by Dave Moll; 28th May 2012 at 10:50 pm. Reason: add alternative |
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29th May 2012, 4:00 pm | #12 |
Dekatron
Join Date: Dec 2004
Location: East Yorkshire, UK.
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Re: Direct Line red phone
Thank's again every one for your help. Following Daves advice I am using an ADSL filter and the phone is now working.
John. |
29th May 2012, 8:18 pm | #13 |
Dekatron
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Re: Direct Line red phone
One last question did these phones have a draw/ tray? mine has runners only.
John. |
29th May 2012, 9:54 pm | #14 |
Dekatron
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Re: Direct Line red phone
I doubt that they were distributed with anything utilising the runners (visible on the attached image). If the number of unpopulated positions on the circuit board are anything to go by, both this and the casing are probably generic Geemarc designs that were used for other 'phones as well.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |