[cisco-voip] Hookswitch problems on IP phones

[jonc]

On Wed, 2005-08-31 at 16:30, Bill Woodcock wrote:
>     > We're starting to see problems with the hookswitches on 7910 and 7940 
>     > phones.  First occurrence was a couple of weeks ago, now 2 more in the last 
>     > week.  Is this a trend, I wonder?  (Phones are about 5 years old.)  Symptoms 
>     > are that when the phone is lifted off-hook, the switch only goes off-hook 
>     > for a brief instant, then goes back on-hook.  The caller only hears a brief 
>     > click followed by a dead line, and the callee gets a bum rap for hanging up 
>     > on his callers.  One of my guys suspects the spring in there is weakening. 
>     > Is anyone else seeing similar problems?
> 
> Yup.  This is about the only hardware problem on the 7910/7940/7960 that I 
> know of, but a lot of us run into it eventually, if we're handling a lot 
> of phones.  I'd guess than 1% of the phones I've dealt with have developed 
> this problem eventually.
> 
>                                 -Bill
> 

Indeed. We have traced that particular problem to the small carbon disk
used in the off-hook sensor. Replacing this (looks to be about a fifty
cent part) normally brings the phone back to perfect working order.

Probably all the carbon disks used in the button sensors are degrading -
but the hook switch sees the most action so it seems to show up there
first.

If you have some junk phones (lightning, coffee floods, etc) take one
apart and pull the small square latex piece off the back of the off-hook
button. Use this to replace the same piece on the problem phone.

If you look at the small latex square you will see the small carbon disk
glued in the middle of it. It's this disk that needs to be replaced.

Too much information. I know... but its fun to bring these guys back to
life. And profitable - I've saved thousands of dollars by doing some
relatively minor repairs on some of our returned Cisco phones (that were
no longer under warranty).

Jon Carnes