cisco 7920 ip phone noise static crackle

Unanswered Question
Nov 1st, 2010

cisco 7920 ip phones (2)

firmware: 7920.4.0-03-02

hardware info 4.0

cisco 1242AG access point

System Software Version: 12.4(10b)JA3

cisco 2651XM router

IOS: c2600-adventerprisek9-mz.124-15.T9.bin

I have a couple of cisco 7920 phones, they are connected to a cisco 1242AG access point which is in turn connected to an NM-16ESW switch in a cisco 2651xm router. The problem is noise and static on both phones and happens with both internal and external (sip trunk) calls. I also have 7940 desk phones on the same router but they do not have any noise problem. What's really weird is if I squeeze the 7920 phone while it's at my ear the static and crackle increases. I tried a different voice codec in the router but it made no difference and I've always used g711ulaw. I also have 'no vad' on the dialpeer. I figured the problem may lay with the access point config but I don't know. Attached is a the access point running config, thanks if anyone can help.

I have this problem too.
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tonyspcrepairs Wed, 01/26/2011 - 09:48

I found a solution for this which may benefit others....

I took my worst 7920 phone (really bad crackle) and dismantled it.  There are two circular bullseye-type contacts at each end of the phones' circuit board. One connects to the ear speaker, the other to the microphone. I got some isopropyle alchohol and cleaned these contacts thoroughly. I also cleaned the back of the microphone piece (it has three contact dots on it) and the spring contacts for the earpiece. While there I also bent the earpiece contacts up a bit so they'd press harder when re-assembled. I also cleaned the contacts on the battery for good measure. Re-assembled - the phone is like new, sound is perfect, no more crackle.


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