BT4500 Big Button phone not working with Digital Voice

[ryan7]

Context:

My grandparents were recently migrated to Digital Voice. They live in the Ashford Surrey area.

They have FTTC and within the house their BT faceplate has the internet and phone split on it e.g it has two sockets. They have a BT SmartHub 2 and get all their phone and broadband services from BT.

They have two telephone extension ports in the house, one upstairs and one down. Both use micro filters, they don't work without these even though I thought the two socket faceplate was meant to negate the need for filters.

The upstairs phone is an old phone, about 30 years old. It's entirely analogue line powered. I don't know much about it's make and model. It has some sliders underneath.

The downstairs phone is a dual set of the BT4500 Big Button phone.

Problem:

I cannot get the BT4500 phone to work, at all. It worked previously before the switchover. It does not work plugged into the BT SmartHub 2 directly or into a paired digital voice adapter when nothing else is plugged into the system. I have tried using the RJ11 (BT4500 phone end) to BT631A cable supplied with the phone (which has just two wires/pins populated of the 6 available) and a different RJ11 to BT631A cable (from an older BT cordless phone they stopped using, this has 4 out 6 wires/pins populated).I also had another spare of each 2 and 4 pin type. None of those 4 cables worked.

In all cases I get an error on the BT4500 stating "check line cord". The old 30 year old phone works plugged into both the digital voice adapter and the BT SmartHub 2 phone port. It just doesn't ring but did start to ring when I use an ADSL microfilter.

My question is, how do I get this BT4500 phone working? At the moment I have at least been able to leave them with one downstairs phone working and ringing.

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[jac_95]

Hi ryan7,

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[rbz5416]

Might be worth a factory reset of the base unit, which should be detailed in the manual. Or maybe the cable was on it's last legs & has died in the move. There are two types of cable, straight & crossover, you almost certainly need straight.

Both the RJ11 & BT431a connectors have six pins, but 1 & 6 are never used. At the BT end, the signal is always carried on 2 & 5. But at the RJ11 end those wires can either also go to 2 & 5 (straight) or to 3 & 4 (crossover). With the aid of a magnifying glass or a heavily zoomed image from your phone, you may to able to just about see the colours of the wires, & therefore identify which is which. You can then rummage in the cable box for a replacement or resort to Amazon/Ebay.

If the other cable is also straight & a reset doesn't work, then it looks like a faulty base.

[ryan7]

It's green and red, pins 3 and 4. Looks like this. This is the cable supplied out of the box. I'll have to try the factory reset then because with several cables tried, I doubt it's the cable, and as it all worked fine before the switchover, thanks for the response.

[rbz5416]

If that's your cable & not a pic from the web, it looks wrong. The RJ11 is connected to 3 & 4, which is crossover. That might be correct but much more likely to be straight & connected to 2 & 5, same as the BT plug.

But if you're saying this is the cable it worked with originally then it must be crossover.

[Keith_Beddoe]

Its odd that its not seeing the line voltage from the Smart Hub 2 socket, unless of course its a voltage issue.

However this page https://bt-digital-voice.blogspot.com/p/bt-smart-hub-2.html does seem to imply that the voltage is still 50V. This extract from that blog mentions pinouts.

"In effect, the Hub's phone socket appears to replicate the output parameters of a master socket, except that the DC voltage on Terminal 2 (B-Wire) is +47.9V with respect to Terminal 5 (A-Wire).  This is slightly lower and in reverse polarity compared with the 50V encountered on a PSTN line.  
(Note the reference to terminal numbering shown on BT socket outlets.  The pin numbering on the BT plug is in reverse order, although it is uncommon to refer to the pin numbers)"

Perhaps its your original master socket that was incorrectly wired, but still worked?

[ryan7]

It's from the web, but only because I don't have time to go back over and grab a picture, but I can assure you that's what it looks like the two cables were in the middle. As to it being wired wrong on the master, not sure, don't know enough. I'll take another look next time when I'm over there and try the reset also. But that seems unlikely if it worked before and the other phone worked okay also?

[rbz5416]

As I said, it might be correct but every piece of BT kit I've encountered over the last 10 years or so has used a straight cable. See if you can find one to take over there to try, just to rule that out.

In the majority of Line Cord errors reported on these forums, it's been due to a mix up of cables.