Warning! Supplied new HomeHub2 modem cable burnt o...

Question

I joined BT Broadband on December 15th, and installed the supplied HomeHub.2 modem that day, using the BT supplied RJ11 to RJ11 cable to connect the HomeHub to the ASDL output on the main phone socket- my landline phone was connected to the other phone output on the main socket.
Everything worked fine, including the Broadband Hub phone, landline phone, HomeHub providing steady Download speed of c.1.9Mps, Upload speed c.395kps, until this past weekend.
On Sunday, I noticed the landline phone started 'crackling and popping' during a short incoming call.
Then the Broadband speed from the HomeHub dropped from the usuak 1.9Mps, down to around 64kps.
I used the 'Restore to Default' setting on the Hub Manager, to try and rectify this, but this then caused--
(1) Despite the normal 4 blue lights being shown on the HomeHub, no Hub phone dialtone was now present.
(2) Broadband speed from the HomeHub stayed at the low 64-76kps
(3) On the landline phone, line noise was so bad it almost drowned out the dialling tone.
Unplugging the HomeHub's RJ11 plug from the main phone socket, restored the landline phone back to normal.
Strangely, if I tried only the HomeHub connected to the main phone ASDL socket, (without the landline phone connected) with the Hub phone plugged into the Hub, this caused the 'Broadband' and 'Phone' blue lights on the Hub, to immediately extinguish.
After a lot of puzzlement, trying out other phones and equipment, etc, I thought to check the modem cable connecting the HomeHub to the ASDL socket on the main phone socket- the cable that has the RJ11 plugs on either end of it, and that were supplied with the HomeHub by BT, only 6 months ago.
I found that the RJ11 plug which went to the ASDL socket, had both of the tiny gold contacts completely burnt out- the surrounding plastic had been burned black and actually had melted through.
I replaced this cable with a spare I had from my previous Wireless Router, resulting in everything working again, as normal, except for my Broadband download speed- this stayed at around 65kps. 
I phoned BT Broadband Tech Help yesterday to report the continuing slow Broadband speed, and was told that "an Open Line Fault had been reported on Sunday at 14.32hrs and this fault was still unresolved" Strange- I didn't report a fault until yesterday?? BT told me the slow Broadband speed could be caused by this problem, and that it could be located at my local telephone exchange (which is 2 miles away) and that it would resolve itself "shortly".
I have 2 main concerns-
a) What caused the RJ11 cable plug to burn and melt? It was only 6 months old, supplied with the HomeHub by BT, and it could have caused my house to go on fire, with serious consequences. Is it part of a faulty batch and has it happened to anyone else? Is the HomeHub.2 faulty, or what, despite it working ok now?
b) Was it this shorting out and burning of the HomeHub's RJ11 modem plug, that has caused my Broadband download speed to drop to the current 65kps, instead of my usual 1.9Mps? Would this have caused malfunction of the Broadband provision equipment on my phone line, down at my local telephone exchange, resulting in although everything is now apparantly working ok with the new modem cable, I'm still only getting this slow download speed? And why only slow download speed, as the upload speed is almost normal?
Any ideas or comments would be welcomed- has this happened to you?
David Grieve, Dumfries, Scotland.

Answer 1

Hi David,
Many years ago I worked as a Test Engineer in a factory that manufactured telephones.
The only thing I can think of that would have melted the RJ11 contacts, is that the contacts must have had a very high electrical current passed through them.
Your equipment needs to be examined by qualified electronics engineer, ideally a telecoms specialist, but I would suspect that if the two contacts are those of the telephone line - if I remember correctly they are refered to as "A" and "B" by telecoms engineers - then all I can think of is there must be a short circuit inside your router shorting out the line - possibly a surge protector inside the modem has failed short circuit.
The only thing that I can think that could possibly cause this problem is is a high voltage, or power surge, on the telephone line caused by a lightening strike. Have you had a thunderstorm lately?
Some years ago, the phone pole outside my mates house was struck by lightening and it blew seven grades of s**t out of his computer. He was using an internal modem at the time that he left permanantly connected to the line, though fortunately the computer wasn't switched on when it happened.
Other than a thunderstorm, I can't really see how a phone line on it's own could cause this damage, as the 50V DC present on the line can only give a small, limited, "wetting" current, and it would take a current of 1 Amp or more to heat the contacts enough to melt the plastic in the connector. During a lightening strike, many hundreds of Amperes can flow to earth, this is the most likely explanation for the problem, as most of the energy would have been absorbed by the spark gaps and surge protectors inside the BT Master socket, but it would take only a fraction of this energy to damage your router.
In my experience the most common cause of damage to phones or modems is by a power surge caused by a lightening strike.
Regards,
Harry.