Ironic tale about ADSL noise splitters/filters...

Hi

My router locked up the other day and while it was off, I thought I'd replace the noise filter with an unused one, as I'd read they can go faulty after a time. The one I'd replaced it with was about the same age, but had never been used, so it was essentially 'new',

This morning, I noticed the Line Attenuation had gone up from 14 to 35db, and the SNR margin had changed from 12 to over 2 million (which was a negative number, I think). The phone was dead too. I plugged the phone directly into the phone socket and it worked which made me think there was a fault with this 'new' filter.

I replaced the filter with the old one (!) and things are fine again (touch wood); the attenuation is back to 14 and the SNR margin is 12 once more!

So what was up with the 'new' noise filter? It just suddenly seemed to die overnight, having worked fine for almost 48 hours. I don't know why the router locked up (that's a separate issue) but if the router's on its way out, is it possible that it somehow fried the noise filter? Or was it just a dodgy filter which left the factory with faults?!

When you look at this page showing what's inside various filters, it becomes quite obvious that the build quality varies enormously.

Capacitors are often a failure mode for many devices at present, and I'm not certain on their shelf life versus use in non-stressful tasks.

Genrally the type of capacitor that fails is the Electrolytic can type that dry out.

Capacitor failure is extremely common in high temperature situations such as computers and power supplies because of the desire to cut costs to the bone capacitors that are insufficient for the job are used. If to small a capacitor is used that can not handle the ripple then the electrolyte will literally boil causing the capacitor to dry out at an accelerated rate.

Long term unused storage does not appear to be a problem except perhaps in really cheap capacitors that have not been made properly in the first place.

Both the filters I used were standard BT ones that I got 5 years ago when I first got broadband. I only replaced the 'old' (used) one with the unused one because I thought it would be a good idea in the long-term. Then 36 hours later, I find the line stats have gone haywire, and the phone's dead. Upon putting the old filter back in place, things were (touch wood) fine again and the phone came back also.

I had the dodgy filter stored in a box with a load of other electrical stuff, so is it possible it got damaged by a magnetic field or something at some point? That's the only thing I can think of really. Unless of course, it was simply a dodgy one that left the factory with faults. It's quite bizarre that it suddenly went wrong during the night last night though. Although having said that, I had noticed my router stats had shown a few errors (bad cells) when normally I get none at all. So it looks like the filter may have been faulty when I plugged it in, and it slowly got worse over the 36 hours!

Edited by deleted (Wed 11-Nov-09 21:16:49)

Sounds like it was faulty from the offset.

I'd dump those filters. There were some bad batches of BT filters around that time.
I had a number of customers who were given replacements, & they were also faulty. Some people had 4 filters & only 1 was within spec & worked.
Newer batches were ok.