Weirder and weirder

[#1]

After a return to normality from the situation covered by my previous posts there has been a week of good stability with the downstream SNRM around 4.6dB. And that is the situation that pertained when I logged on to broadband this morning at07:00.

Suddenly at 08:01 things changed [see attachments] and I am currently back to a downstream SNRM of 13.5dB just as it was before the change for the better last Saturday. This is beyond weird and I am wondering whether I should just repeat the event that caused a change for the better last Saturday i.e. a quiet line test with a corded phone connected via the test socket on the master?!

I will also be raising a new ticket.

[#2]

@BobR 

My guess would be that this is a dodgy faceplate connection. What happens if you go back to using the Test Socket?

I suspect that the QLT is a red herring, it was the removal and replacement of the faceplate that made the difference.

[#3]

@baldrick 

Yes I'm just about to repeat that experiment to see what happens. Will update this thread shortly.  There was nobody in the room this morning when things changed so it wasn't a manual intervention of any kind that triggered the degradation in SNRM. I note also that the Interleaving depth changed form 8 to 4.

This is a complete mirroring of the profile that was in place a week ago.

[#4]

@baldrick 

OK - have had the faceplate off, tested the line again [no noise] and replaced yet again. and the line seems to recover and then goes strange again [see attachment]. Does this look like some kind of failure with the faceplate?

[#5]

@BobR 

What I am suggesting is that you forget the QLT. but take off the faceplate and plug the filter that came with your hub directly in the Test Socket. Connect your hub and phone to the filter and see if that cures your problem.

[#6]

@baldrick 

Sadly I don't have any filters but have ordered a replacement faceplate that I hope will solve the problem. In the meantime I'm synched at 67.958Mbps and seeing a degraded speed of 42.441Mbps with a downstream Noise margin of 17.1dB.

Thanks anyway for identifying the most likely cause.

[#7]

@BobR 

It’s unfortunate that you don’t have a filter, one would have been supplied in the box with your Plusnet hub. Which type of master socket do you have? Is the faceplate held on with two screws or is it the newer type which clips on? These newer ones are known to be problematic, especially if the back box is screwed down tight on an uneven surface, causing distortion. If this was the case a new faceplate might not help. The difference between your synch speed and download speed suggests that the DLM in the street cabinet has slowed your speed to try to compensate for disconnections, the purpose of using the filter was to determine whether or not this was a faceplate problem. 
When trying to find whether a problem is on your side of the master socket there are two tools that you need, one is a phone for a QLT and the other is a dangly filter.

[#8]

@baldrick 

A trip to the attic meant I found a box of old bits n pieces from the ADSL world - I thought they had all been thrown out. So thanks for continuing to make the point.

I hooked a dangly filter I found in there up to the test socket and lo and behold downstream noise margin settled at 4.7dB [that would be my usual] and synch is 64.747Mbps with speed showing as 62.135Mbps. Interleave depth has stayed at 4 as opposed to the more normal 8.

I presume therefore that the faceplate is indeed the problem?

In the meantime I'll carry on with that arrangement it only means I will need to use the corded phone as the extension wiring is disabled.

[#9]

@BobR 

It’s either the faceplate, the fit of the faceplate to the back box or the extension wiring. Leave it this way until you have a new filtered faceplate. Constant disconnects can trigger the DLM to increase the SNR, so don’t provoke it.

When you have your new faceplate make sure that the extension cables are wired to the phone output on the filter. If it’s the clip on model (when ordering the replacement I trust that you are getting the right type, they are not interchangeable), make sure that they fully clip together. If necessary slacken off the back box securing screws.

[#10]

Should be OK - I ordered a replacement filter for the OpenReach MK3 master socket type i.e. the two screws version. 

And of course I wont forget to connect the phone extension wiring.

Thanks for your help.