Storm damaged NDD-0300 NBN FTTC Network Connection Device - Page 1
Forum section: electronics / repair

author: Helix70
author_rank: Unknown
timestamp: June 22, 2021, 04:32:26 am
content: Has anyone on here had a NBN NDD0300 FTTC Network Connection Device stop working after a storm?Mine shows the flashing red light and clicking the relay periodically. I suspect that the device isn't supplying power up the RJ12 any more.Anyone repaired one? Got any hints? No obvious component damage. Any help appreciated.Josh

author: Whales
author_rank: Super Contributor
timestamp: June 22, 2021, 06:03:03 am
content: Massive quantities of these die all of the time in storms. It's apparently a big expensive for the NBN.https://www.theguardian.com/technology/2021/may/18/nbn-to-replace-10000-modems-after-lightning-fries-devices-across-blue-mountainsClicking relay does suggest it's cycling power backfeed on and off (I've read somewhere that these units signal the pit equipment to disable 48V POTS power before they flick the relay and backfeed power?) . Are you sure it's even your FTTC unit that's fried and not the unit out in the pits somewhere?N.B. I believe these modems remain the property of the NBN, but at the same time I guess they don't care too much about already dead ones. Nice photos of the insides please

author: Helix70
author_rank: Unknown
timestamp: June 22, 2021, 09:44:07 am
content: I am sure, they replaced it and I have the broken one. I would like to fix it for next time. I will do some pics soon.

author: SmallCog
author_rank: Frequent Contributor
timestamp: June 24, 2021, 04:08:42 am
content: We had lightning hit the tree next to the pit.Killed both the unit in the pit and the indoor unitAnnoyingly they flatly refused to do any sort of line integrity test between the pit and premises or move us onto a different pair (50 pairs to the building and this is the only copper service)

author: Helix70
author_rank: Unknown
timestamp: June 27, 2021, 06:14:07 am
content: Images as promised.

author: Whales
author_rank: Super Contributor
timestamp: June 27, 2021, 09:42:11 am
content: Wow thankyou!I love how much of it is power supply. Literally a tiny DSL router in bridge mode mated with an oversized laptop brick. Keeping some of the input protection in a tin can is cute (blast containment?)If it died due to a storm: I would start with a DMM to inspect the DSL input protection parts. If they have done their job correctly ("if") then they may have sacrificed themselves to save the more sensitive ICs. Gas tube should be open, fuses should be short, capacitors should not be shorted and transformer/choke windings should be distinct (the last two may require desoldering to test).If that doesn't yield anything obvious: check to see if the relay has welded/exploded inside. You can try and probe it whilst the unit is running, or try and cut the plastic cover off it for a visual inspection (often they don't fall apart and you can watch them working, but it depends on the design). A little bit of darkness on the contacts can sometimes be normal, but anything more than that is suspicious. If the relay has welded or exploded then the modem ICs have probably been fried too and you are probably SOL for the repair.I see four unpopulated pin holes on the DSL board. There is a good chance that is a UART port. Basically all DSL modems have a 3.3V UART at 9600 or 115200 baud 8n1 that gets spammed with boot and operation messages, sometimes these can give you a hint as to what is going wrong (eg "no carrier detected" even when plugged into DSL line). If you're super lucky they also provide an interface you can get a full shell on for full router control. Buy a cheap USB uart if you don't already have one, three jumper wires (GND, RX, TX) is all that's needed for anything reasonably modern (the 4th pin will be 3.3V or 5V, which you can safely ignore). Use a DMM to work out which pin is which. Try different combos of RX and TX until something works. Try different baud rates until you see something other than gobbeldybook appear in your terminal program.

author: johnh
author_rank: Regular Contributor
timestamp: June 28, 2021, 08:17:22 am
content: Big beefy power supply to feed the Fibre NTD in the pitSo the NTD in the pit could be fried as well