This matches with what I've seen/heard/read - the clicking is the NTD turning off/on power to the DPU, while it tries to check if it's coming online.
We had a DOA DPU and have had one since after a storm, in ... under three months. James On 2021-01-25 09:30 Matt Perkins wrote: > There’s nothing quick about a disconnecting relay. But I do have the > reports of them clicking so perhaps power is applied and they are > looking for some condition that does not appear so power is removed a d > re-applied. Whatever condition they are looking for can not be sensed > due to the fault perhaps there’s some type of op-amp in that sense > circuit that’s sensitive to potential difference and the problem lies > there. Wherever the problem lies given the massive volumes involved > there appears to be a design fault / fit for purpose issue at play > here. > > Matt > > > > -- > /* Matt Perkins > Direct 1300 137 379 Spectrum Networks Ptd. Ltd. > Office 1300 133 299 m...@spectrum.com.au > Fax 1300 133 255 Level 6, 350 George Street Sydney 2000 > SIP 1300137...@sip.spectrum.com.au > Google Talk mattaperk...@gmail.com > PGP/GNUPG Public Key can be found at http://pgp.mit.edu > */ > > > On 25 Jan 2021, at 10:24 am, Thomas Jones <m...@thomasjones.id.au> wrote: > > > > There is definitely a relay internally, not sure what it's actually there > > for though - could be for applying power to the line when attempting to > > power the DPU, if a short is detected it can disconnect quickly. > > > > Kind regards, > > Thomas Jones > > > > -----Original Message----- > > From: AusNOG <ausnog-boun...@lists.ausnog.net> On Behalf Of Matt Perkins > > Sent: Monday, 25 January 2021 9:17 AM > > To: Jrandombob <jrandom...@darkglade.com> > > Cc: AusNOG@lists.ausnog.net > > Subject: Re: [AusNOG] Lightning and FTTC - is it really this bad? > > > > They had a few hundred to replace in the eastern suburbs in the first week > > of Jan the cable there is almost all underground. If anyone has one and can > > post a detailed photo of the PCB we can get to the bottom of it but suspect > > the HV protection is non existent. > > > > I have heard mention from customers that there is some sort of clicking > > sound on a dead NTD not sure what that would be why there would be a relay > > in there. Might be just false info Matt > > > > > > > > -- > > /* Matt Perkins > > Direct 1300 137 379 Spectrum Networks Ptd. Ltd. > > Office 1300 133 299 m...@spectrum.com.au > > Fax 1300 133 255 Level 6, 350 George Street Sydney 2000 > > SIP 1300137...@sip.spectrum.com.au > > Google Talk mattaperk...@gmail.com > > PGP/GNUPG Public Key can be found at http://pgp.mit.edu > > */ > > > >> On 24 Jan 2021, at 7:00 pm, Jrandombob <jrandom...@darkglade.com> wrote: > >> > >> Mea Culpa. > >> > >> That makes perfect sense. I was considering it from an RF perspective > >> wherein the mass of earth would theoretically shield the buried > >> copper. I'd failed to consider that in the case of a ground strike the > >> buried copper presents a low-resistance path through the lumped > >> resistance of earth, so it will be the preferential path for the > >> current to take. > >> > >> In which case the best I can offer is that perhaps the apparent higher > >> NTD mortality rate in high lightning areas with aerial lead-ins is > >> maybe due to them being more susceptible to higher-frequency > >> components which are induced RF-wise into the aerial cable? > >> > >> Though without solid data it's hard to say if there's actually a real > >> correlation between the aerial lead-ins and failures. Since most > >> aerial cables end up being underground somewhere along the line it > >> could well be a remote ground strike that is to blame and it's just > >> the human propensity for pattern matching telling us there is a > >> correlation. > >> > >>>> On Fri, Jan 22, 2021 at 12:51 PM Ross Wheeler <aus...@rossw.net> wrote: > >>> > >>> > >>> > >>>> On Fri, 22 Jan 2021, John Edwards wrote: > >>>> > >>>> Underground copper is probably more vulnerable than aerial to lightning. > >>>> Lightning strikes the ground, not the copper, but a voltage gets induced > >>>> in the copper due to the nearby electromagnetic charge - something that > >>>> doesn't happen in air because it's a fairly good insulator. > >>> > >>> My experience has shown a different path to lightning damage. > >>> > >>> When lightning strikes the ground, or a grounded object, that current > >>> dissipates through the soil, which has a typical resistance of around 500 > >>> ohms per metre. If you have tens of thousands of amps flowing, then ohms > >>> law tells us we have potentially huge potential differences over even > >>> fairly short distances. > >>> > >>> The copper cable has a very low resistance (by comparison). > >>> If that cable happens to be radial (or oblique) to the current path from > >>> the point of entry, the potential difference from one end of the cable to > >>> the other will be hundreds to many thousands of volts. > >>> > >>> Even the insulation of the cable may not be enough to save it, and any > >>> components connected to it which happen to be physically close to the > >>> ground will certainly break down. > >>> > >>> This can happen at distances far further away than magnetic induction > >>> alone would explain. It also explains (to me anyway) why I've seen burried > >>> cables damaged part way along their length (where the greatest potential > >>> difference has been). > >>> > >>> Just my take on it. > >>> R. > >> _______________________________________________ > >> AusNOG mailing list > >> AusNOG@lists.ausnog.net > >> http://lists.ausnog.net/mailman/listinfo/ausnog > > > > _______________________________________________ > > AusNOG mailing list > > AusNOG@lists.ausnog.net > > http://lists.ausnog.net/mailman/listinfo/ausnog > > _______________________________________________ > > AusNOG mailing list > > AusNOG@lists.ausnog.net > > http://lists.ausnog.net/mailman/listinfo/ausnog > > _______________________________________________ > AusNOG mailing list > AusNOG@lists.ausnog.net > http://lists.ausnog.net/mailman/listinfo/ausnog > _______________________________________________ AusNOG mailing list AusNOG@lists.ausnog.net http://lists.ausnog.net/mailman/listinfo/ausnog