Reversing A an B

Openreach paid the area a visit last week and true to form my usually reliable broadband developed a faul t (can't they ever fix anything without breaking something else?). Last time the internet stopped every time the phone rang. From experience I tried reversing the a and b wires at the modem socket. Fixed it. This time a deafening hiss appeared on the phone line but the internet held up. Guess what, reversing a and b again fixed it. Filters checked first, sky, fixed phone and wireless phone all OK. Billion router does its best (even have the speed turned down to givea 9,db snr). Any ideas of what causes this polarity sensitivity and how it could be cured ?. Overhead line, adsl2, 53 dB downstream attenuation, 4 MBS usually, unless Openreach are in the village.

The bulk of the ADSL signal comes down the B leg of the pair. Your reversal of the polarity isn't fixing the problem, just masking it.

That doesn't make sense. It's pd between the lines. Pls don't respond again.

In reply to a post by MrOptimistic:

Pls don't respond again.

That's not the way to reply to someone trying to help, especially given Zarjaz's employment

In reply to a post by MrOptimistic:

That doesn't make sense. It's pd between the lines. Pls don't respond again.

ROFL
If you know better than Zarjaz then you wouldn't have asked your question in the first place.

Too funny .

See this thread. Almost identical opening post, January 2014.

I am a casual user of this forum and have always appreciated help and advice, people respond with advice and thoughts and you are asking for that by posting on a community forum, yet one person responds with a theory and you tell them Pls don't respond again. well why don't you do that and go and look for the help elsewhere, because I would like this thread closed @MrSaffron, beacucse of your unappreciated nature.

I think you are over optimistic.

Edited by thomaswarne01 (Mon 18-Apr-16 05:48:53)

Telling a fellow poster to not respond again because something did not make sense is nonsensical, since surely you would be interested in an explanation.

If a poster has done something that flouts the site rules then of course you are free to report it, but you cannot pick and choose who responds in a public forum.

My bad ! Sorry all round. Took umbrage a bit about the certainty that the reversal wasn't the cure but was hiding something else but then just stopped there. My take was thanks very much for that but if you are not going to help why bother and can you not do it again. Made sense at the time but perhaps caught in the wrong mood so sorry again.

Yes this problem has happened before, twice, and I did post here but didn't really get much further with it.

Anyhow, sorry for the rudeness.

Edited by MrOptimistic (Fri 22-Apr-16 12:52:16)

What, no answers about unbalanced lines and earth loops?

You should not be switching A & B yourself.

If this persists you really need to report a fault to your service provider. This is not normal.

Important to note is if you confess to tampering with BT equipment like you have been you will be liable for the repair charges.

Zarjaz is very experienced, so have some respect

Please mark this post as Closed.

Simple answer is report it to your service provider and they can get openreach to investigate,

No need to be rude on here,
that is why no one is replying.

your best friend in this matter will be google.

Period.

No I am only reversing the wires at the extension socket, it's a very old installation with the BT wires arriving at a lozenge shaped junction box. BT just said that the fault lies with my equipment (when the noise was on the telephone), and anyway there is no fault showing now. Not found anything on Google nor read about anyone else with this. Strange.

Try the Quiet Line Test, dial 17070 and take option 2 and listen, if there is noise then report it as a phone line/voice fault (not broadband and don't mention it either) to your phone service provider.

Do you have a master socket? If you do not or even if you do, is there noise on the line?

Edited by ukhardy07 (Fri 06-May-16 20:04:35)

There must be a master socket. There are plenty pre-NTE5. Mostly LJ 2/1As.

The master socket...to explain. When I moved in here 33 years ago the overhead line in to the house was to a junction box then promptly popped outside again, over a roof, through an upstairs window to another junction box affair then to a socket. A separate line ran from first junction box to a down stairs socket. Do the lines were in parallel.

At some point we had BT in and they made the upstairs socket the master and ran a line back to the junction box downstairs and then to the downstairs socket.

At a later date another BT engineer removed the line to upstairs, made the downstairs socket the first point and I ran an Ethernet cable to the upstairs socket on his suggestion.

At various stages I have had third party active sockets upstairs and downstairs. Currently only upstairs feeding the modem.

That's why I am quite relaxed about the master socket business. Technically and legally it must be the downstairs one now I supose but I seem to get on well with visiting engineers and have never had a problem or rebuke.

Glad you asked?

My link has a gallery of sockets.

I am quite relaxed about the master socket business.

That might explain why you have a problem.

Thanks. Can you point me at the link? The input into the downstairs socket is unchanged from when BT put it in, all I did was to take A and B off round the house from a connector post in the socket. There is a piano in the way so not easy to get to but only has a single socket to the outside world. There is no ring wire anywhere.

Only relaxed in the legal sense......

In reply to a post by MrOptimistic:

Thanks. Can you point me at the link?

In this thread, at Sat 07-May-16 11:00:58

The point I was indirectly making there was that knowing the location of the master is a vital factor in vetting and altering your wiring. How it connects to the incoming line from outside, and what else connects where, can hugely affect what goes on in terms of interference pickup on your connection.

Changes you make without knowing which is the master are basically random and "suck it and see". Best is to draw a diagram of all wiring once you know which is the master, upload it somewhere, and let us take a look. Descriptions are very often open to misinterpretation, however hard any of us try either describing our own to other people or reading theirs.

Given that the OP described the outermost connection as being "lozenge-shaped" (Fri 06-May-16 19:43:41), could it be one of the much-older screw-type "boxes" or termination units, given that it appears to be over 33 years old?

" it's a very old installation with the BT wires arriving at a lozenge shaped junction box"

I would then be suspicious of the screws having slackened slightly and/or corrosion, given the photo/s displayed on another thread recently.

--------

As you have requested, he really needs to sketch the present arrangement, with photos or descriptions of each connection, to help clarify the present situation.

Blimey, missed that. OK I'll shift the piano and unscrew the first socket and draw it up. Something I think is correct is obviously wrong so that is a good idea. Will show filters too.

Yes it's an old installation. Thinking back, the line upstairs used to end in one of those old junction boxes that we used to have screwed to a window sill which was hard wired to a phone. I took that out and put in the modern adslnation filtered box years back. The first one eventually failed so the current one is a replacement.

Edited by MrOptimistic (Fri 20-May-16 16:40:10)

In reply to a post by MrOptimistic:

Thinking back, the line upstairs used to end in one of those old junction boxes that we used to have screwed to a window sill which was hard wired to a phone. I took that out and put in the modern adslnation filtered box years back. The first one eventually failed so the current one is a replacement.

We need a layout diagram as well please. And preferably photos of the insides of every socket there is. Otherwise there could be a week of questions and none of us would be certain even then.

If you do resort to a sketch, indicate the type of NTE or other "junction box" used at each joint.

Your mention of "Piano" rang bells from a tale of over half-a-century back.

A colleague had trained as a Post Office Telephone Boy, graduating in to adult service.

One day, his manager asked him to go to a house where one of those rarities, a (land-line) telephone had been installed - just that very day.

The customer had phoned to report a problem; but was almost hysterical and the manager had not been able to comprehend what was the cause, particularly as the customer was using that very phone to complain - and thus it was clearly working.

My colleague jumped in his "glass-house" van of the period, and drove to the location.

As he approached the front door, he noted that the external wiring all looked fine to the two insulators of that era, then the cable came down the wall tidily to the top of the skirting board in the vestibule.

On being admitted, he followed the cable part way in to the hall-way, through a doorway in to the front room, along the the top of the respective skirting boards, to a wall, where the terminating block of the period was mounted, with the new phone on a small table.

Then he suddenly realised that the "wall" was actually the end face of the piano.

It's not that bad. I hope. Issues at work and prob 2 weeks in USA may delay things. I'll dismantle the boxes and see if I can describe the arrangement and identity the box type. Photos might be difficult.

However might have found an issue. The master socket has one input. The line upstairs to the modem goes from inside the socket, unfiltered. There are no other connection internally. However plugging in to the socket are three inputs. Physically these are in to a doubler socket which also has a fixed line from it. The inputs are two phones and the sky box. The doubler socket then plugs into a filter then in to the master socket. So three things hang off the filter.

Doesn't sound like best practice.......

Trouble is I have no way of knowing if separating all lines to give each a filter will cure the issue as until open reach change something there isn't any fault. Pretty sure I unplugged everything bar the old fashioned phone last time but can't honestly say I am sure. Do you think that may be it?

Even with this arrangement the line is very good for a long rural line. 54db attenuation downstream, and margin 9db. Rate 4143 kb. The router is throttled back with and tweak to reduce the rate. Left to its own devices it goes for 3db and a rate in mid 5000's which I reckon is pushing it a bit.

Sky boxes can sometimes need double filtering, particularly older types. So try Sky box into a dangly filter into the doubler. Leave the phone on the other doubler socket where it is, not into the new dangly.

Has the current filter ever been replaced?

"
The master socket has one input. The line upstairs to the modem goes from inside the socket, unfiltered. There are no other connection internally. However plugging in to the socket are three inputs. Physically these are in to a doubler socket which also has a fixed line from it. The inputs are two phones and the sky box. The doubler socket then plugs into a filter then in to the master socket. So three things hang off the filter.
"
Keeping in mind that the Modem/Router should have for its own purposes, a "straight-through" electrical connection with the incoming phone line, you appear to have that correct condition in that extension.

I'm not quite sure of the other connections, ie the doubler socket etc.

If these are "separated" from the incoming BT line by either one filter close to or in the master socket; or by individual filters in each of the onward three lines, picking up on the "PHONE" socket of a typical dongle, that should be OK; aside from total loading, given your long line.

In particular, the "fixed line" from the "doubler" might not be filtered.

Generally, make sure that all of the connections, whether by screws or plugs/sockets, doubler/dongles, are clean, bright and tight.

Oh, that might be that theory shot then. No idea where I got the doubler thingy from. It's like a standard doubler, but in addition has a built in line coming out if it which now goes to a phone. The doubler plugs into the dangle filter which then plugs into the phone box. So all three lines go through one filter. Of course eventually all lines are brought into a parallel connection when they get to the master socket, however with the current arrangement they are connected in parallel before the filter and not after it. That was what I wondered may be an issue.

I recognise that type of doubler, with an extension starting coming out of the doubler, almost as though the doubler is a tripler.

Remember to ensure that all the various connections are clean and bright.

---------

Most will probably have gold plating; and that can give rise to gold crystals, called dendrites, particularly when DC currents are present.

Most solid crystals are poor/non-conductors, so gradually the connection/s deteriorate, so should be opened/closed occasionally, say once per year.

Opening and closing breaks down the dendrites, effectively smearing them back to conducting gold.

http://www.te.com/documentation/whitepapers/pdf/p313...
"
Introduction

Metallic electromigration has long been recognized
as a significant potential failure mode in
many electrical and electronic systems
"

In reply to a post by eckiedoo:

Most solid crystals are poor/non-conductors, so gradually the connection/s deteriorate, so should be opened/closed occasionally, say once per year.

Opening and closing breaks down the dendrites, effectively smearing them back to conducting gold.

Many years back, I was taught one of the first things to consider when fault finding on installed systems was to power down, then pull every board out of the backplane connector re-insert and repeat or wiggle it around left/right/up/down, . Power up and see if the fault was cleared!

As you say, it cleans up the contacts.

Well, I've just installed a new NTE5a master socket and telephone extension at my mother's house.

On looking inside the master socket I discovered that the A and B wires were reversed. This was confirmed by plugging a test telephone into the master socket and using its polarity checker.

This was from a new build back in about 1980. It's never caused a problem with voice, dialup or ADSL.

Everything's sorted now and with the bell wire disconnected and no 26A surge arrestor (which Openreach recently had removed from NTE5a master sockets) the maximum attainable downstream sync has jumped by about 1MBps and upstream has improved slightly. I'm sure the polarity change had nothing to do with this.