[WXC/VFX] Linksys SPA942 hum on line

Forums › One NZ (including Farmside) › [WXC/VFX] Linksys SPA942 hum on line - Any Ideas?

ajobbins

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#15155 7-Aug-2007 11:45

Recently my quite new SPA942 has developed what sounds like an AC hum through the handset (Doesnt affect speakerphone). This kind of comes and goes and increased/decreases in volume as it seems to see fit.

This seems to be getting worse and has got to the point where it is the norm rather than the exception and as a result I have almost completely stopped using the device.

Speaking with Hads at NiceGear he suggested it may have been a grounding issue as the phone is powered via an adapter rather than PoE and that I try grouding it with STP cable (Which wasn't easy to get) to the NIC in my PC - But that didnt help.

Does anyone know what could cause this kind of issue or do you think it is a hardware fault? I would rather not send the device away for service if I can help it but I might not have a choice

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chchmjr

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#81444 7-Aug-2007 13:08

Could be environmental, something like a fluorescent light. Try moving the whole phone while listening to see if the noise comes and goes.
Handsets can go noisy, try a handset from another phone (It does not have to be Linksys).

Michael

ajobbins

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#81446 7-Aug-2007 13:13

We dont have fluoro lights and I have tried completely isolating the device (Well a good several metres) from all other electronic devices with no joy. Also, none of our pots phones have this hum which I would expect if there was some kind of major electrical interferance.

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Niel

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#81467 7-Aug-2007 15:52

I would suspect the power adapter. The smoothing capacitors can fail after a while. Try a different power adapter with the same voltage, same polarity on the connector, and the same or higher current rating. Don'c consider fixing the power adaptor, the case is (plastic) welded together.

However, if it is an AC adapter (e.g. 9V AC instead of 9V DC adapter) then there are no smoothing capacitors in the power adapter and it is actually inside the Linksys unit. This can be repaired, but is only worth it if you know someone that is good (not just average) with electronics. I'm willing to help if you are not in a huge hurry, I've been doing electronics for over 20 years. Just send me a PM.

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ajobbins

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#81468 7-Aug-2007 16:01

The unit is only a few weeks old so therefore still under warranty. The power adaptor puts out 5V DC but the fact the hum disappears when its on speakerphone but is there with the handset would lead me to believe the problem isnt with the power supply

cardcraft

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#81475 7-Aug-2007 17:18

Its to do with grounding on the phone, if the phone was on POE then it would be earthed from the switch. The solution to your problem is to purchase an STP cable and connect that to your computer that will earth you phone and the hum will disappear.

ajobbins

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#81481 7-Aug-2007 17:45

cardcraft: Its to do with grounding on the phone, if the phone was on POE then it would be earthed from the switch. The solution to your problem is to purchase an STP cable and connect that to your computer that will earth you phone and the hum will disappear.

Tried that, didn't work. Also as soon as I switch to speaker its fine so its definately not a grounding issue.

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cardcraft

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#81487 7-Aug-2007 18:57

I have never had that problem that you are describing, but I have had other problems with the linksys phones. Just RMA it i reckon.

Niel

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#81499 7-Aug-2007 20:16

adamj: The unit is only a few weeks old so therefore still under warranty. The power adaptor puts out 5V DC but the fact the hum disappears when its on speakerphone but is there with the handset would lead me to believe the problem isnt with the power supply

A few weeks old: Do an RMA, no point wasting your time on it.

5V: Then it is 99% sure DC and has capacitors in the power adapter which can be faulty. Note that Linksys does not make the power adapters, and is not necessarily of the same quality as the rest of the product (power adapters are "bought in"). However, if it is a lightweight switch mode power adapter then it is unlikely to be faulty, if it is a heavy linear adapter then it is possibly faulty.

No hum on speakerphone: Speakerphone uses a different amplifier than the handset, and it is very much possible that one would have a hum but not the other (irrespective of the fault being the power adapter or not). It is a different circuit with different components.

Bottom line, do an RMA.

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ajobbins

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#81505 7-Aug-2007 21:28

RMA = Possible weeks of downtime = Unhappy adamj

I figured thats what I would have to end up doing. I tried using the handset cord we had for a different phone and the hum was gone. Problem was that the cord was only 2 wire not 4 like the Linksys one and there was no outgoing audio so the problem might be the microphone or something in the handset but seems to be something along the outgoing audio circuit somewhere.

I ran the multimetre over the linksys cord to make sure there were no shorts or anything on it and there werent.

Niel

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#81507 7-Aug-2007 21:34

I had a problem with a Dynalink modem. Couriered it and received it back 2 or 3 days later replaced with a brand new one. The problem with the modem was after 10 minutes of use the Ethernet port started getting errors and then failed. Reasonably easy to diagnose there was a problem, same as with your phone. So should be a short down time for you.

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ajobbins

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#81508 7-Aug-2007 21:40

Even so by the time I send it to the people I purchased it off, they send it to linksys, linksys sent it back to them and they send it back to me we are easliy talking 7 days (Weekend is only 3 days away). Not to mention it took weeks to get one of these units into the country for me to start with so if its faulty I could be down for weeks. There is little/no stock in the country at the moment from what I can tell.

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maverick

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#81532 8-Aug-2007 06:00

May be able to assist again Adam, will send you a pm

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ajobbins

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#81574 8-Aug-2007 13:59

I've just sorted the problem. I continued to play with the device and eventually narrowed the problem down to the microphone in the handset. Opened it up and two of he wires soldered onto the microphone were very slightly touching. Moved it around abit to make sure they couldnt touch and problem solved!

chris021

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#81662 8-Aug-2007 23:38

This seams to be a problem with linksys at the moment.

I have had about a 2% failure rate on the handsets. Out of 130 phones i have had one on a 962 and 2 x 922s. A swift bang against a hard surface *sometimes* does the trick...

chris021

AndrewTD

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#82023 11-Aug-2007 17:17

I have had two handset failures on Linksys SPA IP phones.
Seems to be an all too common fault.

kind regards Andrew TD