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Forum Index : Electronics : Noisy PC speakers, blame NBN Co.
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I've noticed over the last few weeks my amplified PC speakers were making a humming noise when I turned the volume down. With the volume at its normal position, there was no noise, but when I answer the phone first thing I do is turn down the PC speakers at its volume control, as I'm usually listening to music or podcast. As I turn down the volume, the hum got louder and louder. 100Hz hum, so I suspected a dry filter cap. I tore down the speakers, and replaced the 6800uF 35v electrolytic, and did the usual check for dry joints, etc. No improvement! I then discovered if I unplugged the audio cables from the PC, the sound was gone. Was the PC the source. I turned it off, no improvement, so I unplugged its power cord, no improvement. What! Where was the hum coming from? Maybe down a USB cable from a power backup drive? Nope! Network cable? Bingo! I tuned off the router. Still the hum. I unplugged the network cable to the NBN box. Silence! Must be the NBN Box power supply, its a wall wart type of supply, 12vdc at 2amps. Would be about 5 years old now, and runs all the time. Google it, seams like everyone stocks NBN power supply replacements, even Jaycar, so they must fail often. I decided to pull mine apart and see if I could fix it. Cracked open the case and I could see the main filter cap had been warm, the glue around it has separated from its case. After desoldering one leg it basically fell out. The other leg had evaporated. The cap was a Asia'X brand 47uF 400v, 18mm high and 18mm wide. The only one I could find in my collection that would fit was a 22uF 400v cap, that would do for now. I fitted the new cap, filled the gap with some hot glue, and put it back together. Fixed! No more hum in the PC speakers, and this morning I noticed my bedside clock radio sounded a lot better than is has for a few weeks, no static. So I wonder if NBN Co should be sending out replacements? I would imagine there would be thousands of similar power supplies of the same age, with the same fault.   Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Ralph2k6 Senior Member  Joined: 24/09/2017 Location: AustraliaPosts: 129 |
Wow, you get NBN? We're still waiting.. Beenleigh/Yatala region. Enjoyed reading your process of tracing the source, nice one.  Ralph |
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Madness Guru  Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
He has had it for 5 bloody years we are waiting too, still on ADSL1 here.  There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Yeah I was lucky. When I bought the place there wasnt a land line past the property, mobile was as bad as it gets, and I was told no NBN because the tower was behind a hill. Several months later I got a land line put in, and used a yagi to get mobile data for my internet ( expensive ), and then found out I may actually get NBN service! After a LOT of pestering by me, they came out and tested it, good signal. So they eventually installed the gear, and I signed up to get NBN and a node phone. Got the land line disconnected ( it was very unreliable ). Been using NBN since, apart from a occasional outage for a few hours, its been pretty reliable. I'm on a 25-5 service. In the last couple of months my mobile service has also improved. We were a official black spot, only 20 minutes away from a major city, so a new tower was put up about 5km from me at the other end of the valley. I've gone from -110dbm, 0 to 1 bars, phone only works in one room if you hold your arm up in the air, to -65dbm full signal phone works everywhere, even in the steel shed  I've waited years to get service like that.Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6100 |
My unit is 4 1/2 years old so it might be heading in the same direction. Here in Tassie, we tend to run our electronics a bit cooler so they last longer. Jim VK7JH MMedit  MMBasic Help |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I had three modems all fail, each one after about roughly a year of service. So I replaced all the crappy aluminium electrolytics with good high temperature low esr electrolytics, and bolted an 80mm computer fan on top of each modem after drilling the plastic cases top and bottom with enough large holes to give a very free airflow over and around the circuit board. All three started working again, without any other faults, and the one I normally use has continued to work without a problem for about the last three years. Its just high internal temperatures, cheap parts, and planned obsolescence. Let the damned thing breathe, and it will probably go on working forever. Cheers, Tony. |
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