T28P Handset Noise Problems

[fdtcloud]

We have around 100 yealink T28P phones deployed and counting, however recently we have been noticing trouble with a few T28P handsets. The handset begins to make a loud hum and buzzing noise and will not stop until the handset (just the handset not the entire phone) is unplugged for about 8 hours, then it sounds good again. The temporary solution has been to replace the troubled handsets and they work just fine. Is this a known issue?

[Yealink Support]

Hi fdtcloud,

1. Can you tell me the version of T28P?
2. Do you test the handsets to the headset port?
3. Do you mean that when you repace a new handset and phone can work well?

Please contact with your seller for RMA and testings.

[fdtcloud]

1. Are you looking for a revision number?
2. Yes tested to the headset port the handset still sounds poor
3. Yes I replace the handset and the phone works well and after about 8 hours I can use the "failed" handset again and it will work well for several weeks before having the issue again.

[Yealink Support]

Hi fdtcloud,

The reason is that your handsets along with helix lines are broken. Please ask your seller for RMA.(Please replace with new handsets along with new helix lines. )

[braymond]

I had the same problem with 3 T2xP phones so far. I am an early adopter of Yealink product and I start wondering if I should move to another phone provider ...

It is easy saying to replace them but when I have to drive 30 km to replace a handset, the profitability goes to the grave.

Not to mention it gives my customers bad perception about the quality of products I provide.

Another feedback I got is if you stretch the helix cord too much, you loose or patially loose audio.

Yealink, you should consider improving the quality of your handsets.

Thanks
Benoit

[Yealink Support]

Hi Benoit ,

Sorry for the inconvenience. Can you supply SN numbers for me? I need to check with our factory about this product problem.

[braymond]

4101313044400001
4101313044400116
4100313044400168

Thanks,
Benoit

[Yealink Support]

Hi Benoit,

Thank you. If any update, i will contact with you asap.

[fdtcloud]

Please update the forum or email me too with an update. I have had a few more do the same thing.

[temp0001]

I came across this issue with one handset last week.
I found that when the curly cord is closer to other electrical wires, the hum/buzzing gets worse. I swapped the curly cord with a known good one, and the problem persisted, indicating the fault lies in the microphone.

As others have done, unplugging the handset for a period of time resolves the problem.

It seems that the electret condenser microphone in the Yealink handset can develop an over sensitivity to hum fields if left powered on for extended periods. The microphone is always powered - I discovered this by putting the headset up to my ear whilst holding down the hook switch with my other hand, I can still hear sidetone.

Maybe if an electrical bias develops on the microphone, causing an imbalance on the two microphone wires, makes it is more susceptible to picking up hum and interference. My theory is that disconnecting the handset allows the charge to dissipate in the dielectric of the condenser microphone, allowing it work normally again.

Maybe a potential fix (that the Yealink engineers can apply to new firmware) is to turn off the power supply to the microphone when the handset is on hook?