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Old 26th Mar 2024, 11:56 pm   #1
mpaxton
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Default 746 Phone wiring - doesn't ring connected to VOIP router

Hello everyone,

I'm looking for a little help with my classic 746 phone that I'm trying to hook up to my internet router-based phone line.

I can listen/talk on the phone perfectly, but it just doesn't ring when.. "rung" I didn't want to mess up the original cable, so butchered a spare RJ11 lead to wire in the "modem" to the phone to start with (you can see this on top on the pic).

I can meter out the terminals when ringing, and detect the 50v AC ring signal.

From looking at the board inside, it looks like the C1/2 capacitor is missing, which I understand is a common issue... I'm in The Netherlands, and don't have a microfilter handy to test with (of course I threw out 3 of them 2 months ago before I started this project..), instead I hooked up a couple of 490uF caps in parallel across the terminals and didn't get anything.

Can anyone take a look at the wiring and suggest what to try? Perhaps an experienced eye will spot it in seconds or you can at least help with some fault finding steps.

I've attached a picture of the board but can always do some more if anything isn't clear.

Thanks in advance!
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Old 27th Mar 2024, 8:27 am   #2
Station X
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

My first thought is that two 490uF capacitors in parallel (980uF) is way too high! The originals were two 0.9uF capacitors in parallel totalling 1.8uF.

http://www.samhallas.co.uk/repositor.../0000/N846.pdf
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Old 27th Mar 2024, 9:23 am   #3
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Looking at your image, a 1.8µF (as Graham says, or thereabouts) capacitor needs to go between T6 and T8 (given that you say there is no capacitor between T7 and T9) and the line connection between T8 (B leg) and T16/17/18/19 (A leg). Although the A & B legs are traditionally connected this way round, it would also work with them reversed.

Am I right in thinking the black lead with red and green wires is what you are using to connect to the VoIP router?
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Old 27th Mar 2024, 9:37 am   #4
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Thanks for the quick reply!

I was referring to this diagram for reference BTW, I think it was posted in a thread elsewhere on the forum. http://www.stevegs.com/projects/tele746/tele746cct.png

But now you point it out, that's many silly mistakes on my part. I was aiming for approximately 900nF (reading C1/2 as needing to be 900nF), I must have thought I was using 2 470nF caps at the time to get 940, but now I look at them again the code is u47K63. So not only did I aim for 1000 x too much, but in reality I didn't even do that and got more like 100 x too much.


I'll head back to the parts drawer and look for the correct ones!! Seems funny the space for C1/2 is massive on the PCB, but I'm pretty sure the real component is going to be even smaller than the 47u ones.
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Old 27th Mar 2024, 9:42 am   #5
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Quote:
Originally Posted by Dave Moll View Post
Looking at your image, a 1.8µF (as Graham says, or thereabouts) capacitor needs to go between T6 and T8 (given that you say there is no capacitor between T7 and T9) and the line connection between T8 (B leg) and T16/17/18/19 (A leg). Although the A & B legs are traditionally connected this way round, it would also work with them reversed.

Am I right in thinking the black lead with red and green wires is what you are using to connect to the VoIP router?
Yes, those go to the RJ11 plugged into the router, an "ExperiaBox 10" which is a standard wifi router, with telephone socket outputs. https://nl.hardware.info/routers.9/z...box-v10.280129

As mentioned silly errors on my part so far.
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Old 28th Mar 2024, 6:43 pm   #6
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Hi, as has already been mentioned, you need a "ringing capacitor" in your phone, either soldered in the C1/2 position or across terminals T7 and T9.
The capacitor needs to be non-polarised either 1.8uF or 2uF and have a working voltage of around 250 Volts AC.

Once you have the capacitor fitted suitably, you need to wire your phone to "two-wire" working as follows -

Strap T4-T5-T6-T7
Strap T8-T9
Strap T16-T17-T18-T19

The red of your RJ11 cord connects to T8
The Green of your RJ11 cord to T18

Regards

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Old 30th Mar 2024, 1:19 pm   #7
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Can I just clarify whether your VoIP port on the modem works with pulse dialing directly? From my research it seems these devices are generally quite rare.
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Old 30th Apr 2024, 4:43 pm   #8
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

I've just gone to FTTP with the land-line option, and Fibrus provided me with a Grandstream VOIP plug-in box. It supports a REN of 5 over a 1km line according to the online manual, apparently.

The telephone socket interface coming out just uses pins 2 and 5 and has no internal ring capacitor (expects a modern 2-wire electronic telephone, I expect), but all I did was remove the incoming copper pair to my now-redundant BT master box and replace them with wires 2 and 5 from my Grandstream box via a short length of flat telephone cable Kroned in to the original Master LJU terminals A and B wires, from which all my house telephone wiring emanates. All magneto-bell telephone ringing works fine, although the ringing cadence is as the U.S. and not the UK traditional one.

I tried LD signalling both on a dial and on a precise electronically-generated LD telephone but doesn't work, even though the line loops when a number is dialled. Nothing in the online Grandstream manual about LD signalling, so guess it's a no-no.
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Old 30th Apr 2024, 8:06 pm   #9
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Quote:
Originally Posted by russell_w_b View Post
.

I tried LD signalling both on a dial and on a precise electronically-generated LD telephone but doesn't work, even though the line loops when a number is dialled. Nothing in the online Grandstream manual about LD signalling, so guess it's a no-no.
If dialling breaks the dial tone, then that indicates all is not lost!!

Most Grandstreams support the US implementation of LD dialling (albeit undocumented) which has a different mark-space ratio than ours and also they have less margin for error than a proper exchange linecard.

I believe the solution is to bend the dial contacts slightly closer together to increase the dwell time.
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Old 1st May 2024, 8:27 am   #10
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

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Originally Posted by Graham G3ZVT View Post

If dialling breaks the dial tone, then that indicates all is not lost!!

Most Grandstreams support the US implementation of LD dialling (albeit undocumented) which has a different mark-space ratio than ours and also they have less margin for error than a proper exchange linecard.

I believe the solution is to bend the dial contacts slightly closer together to increase the dwell time.
Thanks, Graham.

It so happens that I have a U.S. Western Electric 1970s dial telephone down the shed. I’ll ty that and see what happens. It works fine on UK system but speech network is set up differently and transmitted signal is quieter. But that’s by-the-by.
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Old 5th May 2024, 7:20 pm   #11
mpaxton
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Quote:
Originally Posted by AndiiT View Post
Hi, as has already been mentioned, you need a "ringing capacitor" in your phone, either soldered in the C1/2 position or across terminals T7 and T9.
The capacitor needs to be non-polarised either 1.8uF or 2uF and have a working voltage of around 250 Volts AC.

Once you have the capacitor fitted suitably, you need to wire your phone to "two-wire" working as follows -

Strap T4-T5-T6-T7
Strap T8-T9
Strap T16-T17-T18-T19

The red of your RJ11 cord connects to T8
The Green of your RJ11 cord to T18
I stuck in 2 460nF capacitors I could get hold of (of course on the day I go to get it someone had taken half the supply for "sorting"...).

I wired as mentioned, now it rings! Thanks!

I'm not sure if the Dutch ring signal is different but I get a ring which is a single slow repeating ring, rather than the "ring ring .... ring ring" I was expecting. It could be that the ring is just "Dutch" or could it be the capacitor is a little low compared to the ~2uF and it's thrown it off?

Next job is outgoing dialing....
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Old 7th May 2024, 9:31 am   #12
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Quote:
Originally Posted by mpaxton View Post
I'm not sure if the Dutch ring signal is different but I get a ring which is a single slow repeating ring, rather than the "ring ring .... ring ring" I was expecting. It could be that the ring is just "Dutch" or could it be the capacitor is a little low compared to the ~2uF and it's thrown it off?
I would've thought the ringing cadence would be down to the VOIP interface you have plugged in to your router? It will be from here it is generated. I mentioned above that mine is a Grandstream (U.S.) interface box, and my ringing cadence is like it is in the U.S.A. as opposed to the UK ringing cadence.

Maybe there's a way to program it?
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Last edited by Station X; 7th May 2024 at 9:39 am. Reason: Quote fixed. Please use the preview button before submitting a post.
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Old 7th May 2024, 5:28 pm   #13
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Quote:
Originally Posted by russell_w_b View Post

Thanks, Graham.

It so happens that I have a U.S. Western Electric 1970s dial telephone down the shed. I’ll ty that and see what happens. It works fine on UK system but speech network is set up differently and transmitted signal is quieter. But that’s by-the-by.
Right... Tried that. Noooo! Must be some setting-up to do. Also noticed that whenever my Grandstream VOIP box gets data back (the Internet has been off odd times) the Panasonic cordless phone I use in the living room sets its time-display to Eastern Zone US time!
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Old 7th May 2024, 5:30 pm   #14
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

The Netherlands among many others has 1 second ring, and 4 silent. That is probably the std setup at the ExperiaBox 1. (= to the Norweginan telco setup, and they do not give you the possibility to change it) If you are allowed to use a Grandstream, or Linksys unlocked ATA you may change it. Grandstream may read rotary dials, Linksys does not.
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Old 12th May 2024, 11:23 pm   #15
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Default Re: 746 Phone wiring - doesn't ring connected to VOIP router

Bit of a bodge, but in my second life as a systems engineer, many customers wanted a phone changed from "system" to POT. ONLY MOD, add a ring cap inside the socket. My supplier gave me master sockets as all I had to do was cut out caps to make masters into slaves and add cap ( soldered wires on caps, with heatshrink ) added to socket. Meet a master to slave- simple, add cap.
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