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Old 27th Jul 2020, 3:48 pm   #41
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Default Re: A phone too far ...?

Sorry - post #39 should say 'T6 - T5 connected to pin 4 of your telephone plug)'.
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Old 27th Jul 2020, 4:14 pm   #42
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Default Re: A phone too far ...?

Russell: not sure I understand all the theory and equations ( by which I mean I haven't a clue ), but if I ever need a warp core breach sorting out, you're definitely the chap I'll come to!

Joking aside ... first experiment then, as per TonyDuell's post below: removed resistor from phone A, didn't replace it with a strap ( i.e. bell left open-circuit ). Resistors still in B, C & D at this point. Results exactly as predicted: A doesn't ring at all ( as you wouldn't expect it to, short of magic ), B, C & D all ring exactly as they used to when there was no fourth phone in the equation, or if you like, exactly as they do when the fourth phone (A) is unplugged altogether.

To a layman, this seems to me to suggest that something in phone A is causing the problem, although Heaven knows I've no idea what it would be. I say this simply because with no phone A in the circuit, everything seems to work hunky-dory.

If I've done this right ( and I do say 'if' ), there should be two photographs with this post, essentially identical, of the strapping and circuitry inside the back of phone A, if that helps. The strapping appears, from what I can see, to conform to Russell's spec.

Any other thoughts gratefully appreciated; other than that I'll continue experimenting as and when time permits.
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Old 27th Jul 2020, 4:16 pm   #43
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Default Re: A phone too far ...?

If the colour coding of your line cord is white/green/blue/red (to pins 2/3/4/5 of the plug respectively), then pin 4 is the blue wire.
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Old 27th Jul 2020, 4:22 pm   #44
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Default Re: A phone too far ...?

Which ... is correct, then, yes?
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Old 27th Jul 2020, 4:29 pm   #45
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Default Re: A phone too far ...?

Thank you for the image. Yes, by the straps between T6 and T7 and between T8 and T9 being absent, you have disconnected the internal capacitor, and the ringer is being fed via the blue line cord wire from the capacitor in the socket.

The wiring should work as shown.

By showing that your problem goes away when you remove any connection between T4 and T5, you have narrowed it down to the ringer circuit itself. With the resistor between T4 and T5 restored, you could try repeating the exercise with the strap between T16 and T17 removed. This should have the same effect as removing T4 to T5 in that the other 'phones will behave as though A were absent. If so, it would appear that the fault lies within the ringer itself.
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Old 27th Jul 2020, 4:52 pm   #46
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Default Re: A phone too far ...?

Quote:
Originally Posted by Dave Moll View Post
'If so, it would appear that the fault lies within the ringer itself.'
Telephone Guy: have you access to a multimeter? It would be interesting to see what resistance the bell bobbins actually are. Have you also got a piece of steel hacksaw blade or similar you can lightly touch around the pole pieces and compare the residual magnetism with that of the other bells?

Any chance of a photograph of all the bell movements?
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Old 27th Jul 2020, 5:21 pm   #47
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Default Re: A phone too far ...?

Well, one thing at a time ... firstly, unfortunately I don't have a multi-meter ( unless one turns up in the studio gear that I'm in the slow process of unpacking and setting up, in which case I'll let you know ). The problem with comparing one bell-set with the others is the same as the problem with providing photographs: each time I do this I have to unplug the phones ( you may say I'm being unnecessarily cautious, but the one experience I had of touching the wrong two terminals when there was an incoming call has put me off risking it again ). Unfortunately two of the sockets are in quite inaccessible positions, which makes it awkward to do this, especially repeatedly. However, if and when circumstances permit, and depending on anyone's thoughts after this post, I'll do what I can.

So experiment #2 was to remove the strap between T17 & T18. Again, it's as if phone A is no longer plugged in, i.e. the other three ring normally. If I replace that strap with a resistor ( as well as the existing resistor now between T4 and T5 ), I'm back to the situation where phone A rings loud and clear and the others barely make a sound; for all practical intents and purposes, although I'm sure they make a difference in terms of current, the resistors don't appear to make any audible difference whatsoever.

To summarise: with a resistor between T4 & T5 and a resistor between T17 & T18 in phone A, and resistors between T4 & T5 in all other phones, to the naked ear it's exactly as it was when none of the phones had resistors in: phone A rings loud and clear and phones B, C & D barely ring at all.

At the time of writing I haven't yet checked the strapping in phones B, C & D to ascertain whether or not they conform to the same spec. as phone A; I'll post accordingly as and when I've done so.

Again, just volunteering ideas from the brain of a relative layman, but is it possible that the problem doesn't lie within phone A ( despite the evidence ), but rather, with the wiring to the socket into which phone A is plugged ( in which case I'm stuffed, because there's nothing I can do with that )?
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Old 27th Jul 2020, 5:36 pm   #48
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Default Re: A phone too far ...?

Have you more than one master socket on your system that would give you a different capacitor value to your bells and are wires 2, 3, 5 contiguous to all sockets?
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Old 27th Jul 2020, 5:41 pm   #49
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Default Re: A phone too far ...?

Quote:
Have you more than one master socket on your system?
Not to the best of my knowledge. All of the phone wiring was in place when we moved in. The master socket, into which phone B is plugged, is in my office, under and behind a desk; as far as I know, the others are all just extension sockets. Without disassembling, is there any visual way to tell?
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Old 27th Jul 2020, 6:10 pm   #50
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Default Re: A phone too far ...?

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Without disassembling, is there any visual way to tell?
'Fraid not. But it would be worth unscrewing the front plates and checking, just for a 'visual' in any case. Once you're satisfied all is correct you probably won't need to go in there again.

It sounds like your bell-shunt wire is contiguous because otherwise you'd get 'tinkle-bell' on the phones you're not dialling out on, and all the bells are ringing (sort of) when you request it. But you could swap phones around in any case to eliminate any doubts about this.

A multimeter, even a cheap tenner job (or less, in some places) would come in for all sorts of things, as well as telephonery!
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Old 28th Jul 2020, 3:04 pm   #51
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Default Re: A phone too far ...?

Are we all sitting comfortably?

Firstly, here are the requested pictures of the strapping inside all four phones. As far as I can tell they're all identical, except for the fact that phone A ( the newest addition ) still has two resistors in it. I don't know whether these images will tell anyone anything, but here they are for what they're worth.

I'm very much hoping this isn't going to be a 'doh' moment, but ... I'd forgotten the fact that the office phone has a scanner attached ( a CD1000 as per the image ). To be clear, when I say 'attached', the scanner itself has an oblong box hard-wired to the end of it which has a plug that goes into the wall socket, and a socket on the back into which the phone ( C ) is plugged. I don't know whether this makes any difference or not; for what it's worth, I've tried taking the scanner out of the equation and plugging phone B directly into the socket, and it makes no audible difference to the ringing of any of the phones.

Speaking of sockets ... inspecting them from the inside unfortunately isn't an option, or at least not for the purposes of this exercise. The master socket ( into which, as a matter of interest, phone C is plugged ) is in a cupboard which is difficult enough to get into even for the purpose of plugging and unplugging the phone, never mind actually dismantling and reassembling the socket. The living room socket is actually behind a 3-metre wide TV unit which is fixed to the wall, with a fly-lead that goes to the actual phone ( B ) itself. For better or worse, unless someone tells me I might find gold in one of them, the sockets are going to have to stay as they are.

The last experiment I did might ... I do say 'might' ... reveal something; tell me what you think.

I unplugged phone A ( the newest addition - still got two resistors in it ) and phone B ( living-room - one resistor, as per all of phones B, C & D ) and swapped them around. When I did this, phone A, plugged into what would normally be the fly-lead that supplies phone B, did not ring at all, not even slightly. Phone B, plugged into the socket which up to now has been used by phone A, rang normally.

Make what you like of that, and by all means, if it makes sense to anyone, feel free to pass your wisdom this way.
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Old 28th Jul 2020, 3:42 pm   #52
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Default Re: A phone too far ...?

I see phones B & C have gas-gaps in them (surge arrestors). If these went soft they would short out the bell when a ringing voltage was present, but the phones would still work on loop. But likely you have tried all phones individually on a socket, and they all ring individually.

Have you got a pal who has sufficient telephone socket capacity to test all your phones? There appear to be a few variables here hitherto undisclosed and it would help if you went onto another line with no extraneous attachments.

Not sure if the socket on your scanner through which phone C is plugged has its own filter / bell wire capacitor fitted. But because a difference on one part of the line will upset the balance on the other parts - the load has to be calculated as a whole and we now don't know what's in there - you'd be better testing your phones on a known 'good' circuit elsewhere. Preferably a place with one master socket, three extensions (double adaptors would do) and nothing else.
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Old 28th Jul 2020, 3:45 pm   #53
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Default Re: A phone too far ...?

Quote:
Originally Posted by Telephone Guy View Post
'again, is this something I should do? I'm reasonably sure each phone will ring normally individually ( at least, they did when they were last in use at my previous address ).'
I think there's a clue here...
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Old 28th Jul 2020, 4:45 pm   #54
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Default Re: A phone too far ...?

I don't know whether all exchanges are the same, but the ringing voltage (nominally 75V rms) is generally superimposed on the 50V d.c. present across your telephone pair.

Was your previous address on a different exchange to the one you are on now?

What if you were on an exchange where the 50V d.c. was replaced by the ringing voltage rather than superimposed upon it, putting a peak ringing voltage of 106V across the gas gap (spark gap) in your B and C telephones? They might withstand that and you wouldn't know.

Now... Suppose you move your telephones to your new address where the exchange ringing voltage is superimposed upon the 50V d.c. You now have a peak voltage of 156V every half-cycle, which might take the gas-gap low-resistance and shunt the line, greatly affecting your ring signal.

This is a long shot but it has to be considered.
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Old 28th Jul 2020, 6:59 pm   #55
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Default Re: A phone too far ...?

Quote:
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As far as I can tell they're all identical, except for the fact that phone A ( the newest addition ) still has two resistors in it.
I can only see one resistor in 'phone A. Where is the second one?
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Old 29th Jul 2020, 6:56 pm   #56
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Default Re: A phone too far ...?

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Originally Posted by Telephone Guy View Post
Are we all sitting comfortably?

swapped them around. When I did this, phone A, plugged into what would normally be the fly-lead that supplies phone B, did not ring at all, not even slightly. Phone B, plugged into the socket which up to now has been used by phone A, rang normally.
This has been a tail chaser for sure.
I am by no means an expert...
But it sounds like you are battling phone differences, as well as socket differences. Not a good place to be.
I do not know anything about your cabling, but would suggest finding a common place to start from.
You say you have a MASTER as well as SLAVE sockets...
Maybe you could unhook the cap from the master feeding the slaves, it may help if possible
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Old 29th Jul 2020, 8:52 pm   #57
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Default Re: A phone too far ...?

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Maybe you could unhook the cap from the master feeding the slaves, it may help if possible
Welcome to the merry-go-round! The only advantage I can see in unhooking the cap from the master is it would tell you if there was a sly cap elsewhere on the system between line connections 2 and 3 when an attempt is made to make the phones ring. I can see where you're coming from, mind. So yes... Worth a go.

But evidently the master socket is somewhat inaccessible.
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Old 29th Jul 2020, 9:26 pm   #58
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Default Re: A phone too far ...?

Do your phones have a series cap in line with the ringer, located inside the phone?
or is that what the master socket is for?
ours all have their own cap in each phone. nothing inside the socket.
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Old 29th Jul 2020, 9:34 pm   #59
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Default Re: A phone too far ...?

As all 'phones are wired for third-wire ringing, disconnecting from the capacitor in the master socket should stop all ringing. As Russell implies, any 'phone that still rings hasn't been converted for three-wire ringing - or a slave is actually a spurious master.
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Old 29th Jul 2020, 9:46 pm   #60
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Default Re: A phone too far ...?

Quote:
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'or a slave is actually a spurious master.'
I was wondering about that BT CD1000 thing, Dave, as to how the socket might be configured - like an ADSL filter perhaps? But when I looked it up, it looks just like a 'piggy-back' socket as you find on some plug-in extension leads.

Really, to make any progress, I reckon it will be best to invest in a little time and check out each socket, taking copious photos so reference may be made without diving in again.
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