PDA

View Full Version : phone noise from modem


16k_zx81
04-05-2011, 01:33 AM
A few months ago, a customer asked me to set up his new laptop and remove an old machine that was connected to his DSL modem.

I removed the old machine, installed a surge protection board, and set up the Laptop with his monitor, keyboard, and DSL modem.

He phoned me a few days later, complaining that he had noise on his phone, that only occurred when the router was on.

I went back to the house, and, sure enough, whenever the modem was switched on, there was a loud 'hissing' noise going through the handset. The DSL line signal itself appears to be stable, with a consistent, working internet connection. In other words, the issue only appears to affect the phones.The modem is wired, and does not output a wireless signal. The handsets are wireless.

This is what I have tried, after setting up isolation by disconnecting all other phone-related devices:

1. swapped out modem to a new unit
2. replaced all DSL line filters
3. Run a line straight from wall outlet in another room to the modem, bypassing the local wall outlet, different cable.
4. tried a different phone (new handset)
5. Run power from a wall outlet in a different room
6. Run a new RJ45 from modem to PC
7. Tried a different PC (If you think this is starting to sound desperate, its because at this point Im 4 hours and two separate visits into the job and no sign of any improvement in the hiss, and so, clutching at straws just trying everything I can think of.)

Lastly, drew a line diagram of the devices, everything I had tried, and suggested he get his telecomminucations provider in to check the in-wall wiring, which he has done, with no resolution.

Im stumped. The customer has been extremely patient, but is starting to get fed up, especially as its likely now that the telecommunications provider will be charging him $200+ for the line test. I think he's come to the end of his tether, as have I.

Anyone?

Ive never encountered this before, and cant fathom why, after swapping everything out, there is still this abominable line noise on the phone. They can barely have a conversation on it, and the finger is pointed firmly at me, as the problem didnt apparently appear until I connected the laptop to the DSL.

Suggestions regarding what to do with this? Please?

red12049
04-05-2011, 01:55 AM
A few months ago, a customer asked me to set up his new laptop and remove an old machine that was connected to his DSL modem.

I removed the old machine, installed a surge protection board, and set up the Laptop with his monitor, keyboard, and DSL modem.

He phoned me a few days later, complaining that he had noise on his phone, that only occurred when the router was on.

I went back to the house, and, sure enough, whenever the modem was switched on, there was a loud 'hissing' noise going through the handset. The DSL line signal itself appears to be stable, with a consistent, working internet connection. In other words, the issue only appears to affect the phones.The modem is wired, and does not output a wireless signal. The handsets are wireless.

This is what I have tried, after setting up isolation by disconnecting all other phone-related devices:

1. swapped out modem to a new unit
2. replaced all DSL line filters
3. Run a line straight from wall outlet in another room to the modem, bypassing the local wall outlet, different cable.
4. tried a different phone (new handset)
5. Run power from a wall outlet in a different room
6. Run a new RJ45 from modem to PC
7. Tried a different PC (If you think this is starting to sound desperate, its because at this point Im 4 hours and two separate visits into the job and no sign of any improvement in the hiss, and so, clutching at straws just trying everything I can think of.)

Lastly, drew a line diagram of the devices, everything I had tried, and suggested he get his telecomminucations provider in to check the in-wall wiring, which he has done, with no resolution.

Im stumped. The customer has been extremely patient, but is starting to get fed up, especially as its likely now that the telecommunications provider will be charging him $200+ for the line test. I think he's come to the end of his tether, as have I.

Anyone?

Ive never encountered this before, and cant fathom why, after swapping everything out, there is still this abominable line noise on the phone. They can barely have a conversation on it, and the finger is pointed firmly at me, as the problem didnt apparently appear until I connected the laptop to the DSL.

Suggestions regarding what to do with this? Please?

Is there a filter between the phone and jack? Something like these:

http://www.google.com/#q=adsl+phone+line+filter&hl=en&prmd=ivns&source=univ&tbs=shop:1&tbo=u&ei=V2iaTYmvNIuXtweOhLiCDA&sa=X&oi=product_result_group&ct=image&resnum=3&ved=0CEQQzAMwAg&biw=1437&bih=813&bav=on.2,or.r_gc.r_pw.&fp=9fa3ce63015aec7d

Rick

16k_zx81
04-05-2011, 06:09 AM
Is there a filter between the phone and jack? Something like these:

http://www.google.com/#q=adsl+phone+line+filter&hl=en&prmd=ivns&source=univ&tbs=shop:1&tbo=u&ei=V2iaTYmvNIuXtweOhLiCDA&sa=X&oi=product_result_group&ct=image&resnum=3&ved=0CEQQzAMwAg&biw=1437&bih=813&bav=on.2,or.r_gc.r_pw.&fp=9fa3ce63015aec7d

Rick


Yes. There is. (2.). Replaced them.

NorCal Internet
04-05-2011, 10:00 AM
Is there a filter between the jack and the modem? What you're descibing certainly sounds like the DSL modem.

What brand/model is the DSL modem?

westom
04-05-2011, 05:14 PM
Ive never encountered this before, and cant fathom why, after swapping everything out, there is still this abominable line noise on the phone. I have seen similar. One anomaly that can explain it is a high impedance short to earth. Can create leakage currents that would result in noise.

Disconnect phone wires where it connects to the telco's (at the demarc). With a digital multimeter, measure each wire to ground for a high ohm leakage. Each wire should never report less than 10 Megohms to the building's earth ground.

One way this could happen is a calcium growth from a concrete wall into a phone line junction.

If you do not find it in the building, then it might be on the telco wire. But you cannot measure high ohms with the CO still connected to that wire. Linemen must do it.

Meanwhile, also confirm that all wire are connected with their matching twisted pair. Using one wire from two different pairs also causes strange problems.

I did not see it. But you connected a DSL modem directly to the demarc. Then connect all other wires to all other phone via a DSL filter. Necessary to eliminate 'surprise' wiring. Probably not relevant to your symptoms. But standard as a first test when strange events occur.