[cisco-voip] Strike 2 - Dead 7940G IP Phones

[David Sullivan]

cisco-voip-bounces at puck.nether.net wrote:
> Waiting on my network admin to get in so I thought I would
> send this out and see if anyone has seen this before.
> 
> Tuesday morning 3:00am, a single IP phone (out of 200) on our
> network (being used by the single call center agent on that
> shift) loses connection to the network and shows "Ethernet
> Disconnected" on the phone screen.
> 
> We are using Cisco 3560 switches for our user network with
> POE from the switch.  Ethernet cable from the wall to the
> phone and from the phone to the PC.
> 
> Did not think much about it at that time, just figured it was
> a bad phone.  First one since our deployment last July.  I
> replaced the phone with a spare and sent the bad one back to Cisco
> under RMA. 
> 
> In testing the bad phone, it seems that the internal network
> switch is completely dead.  After the initial failure it
> showed "Ethernet Disconnected" on the screen so it was still
> getting POE from the switch.  When disconnected and moved to
> another network port, it will not come back on with POE.  I
> had to use a power cord to supply power and the phone still
> shows "Ethernet Disconnected".
> 
> Everything was fine all day Tuesday, and Wednesday.
> 
> Thursday morning, 3:00am, exact same problem on exact same
> network port, killing the replacement phone that was
> installed on Tuesday.  Everything is exactly the same even
> down to the time of failure.  Phone exhibits the exact same
> symptoms.  Was responding to POE but showing Ethernet
> Disconnected until disconnected from the network.  After
> disconnection, the unit only responds to power from a cord,
> and not POE.  Still shows Enet Disconnected.
> 
> Is the POE coming from the switch on this port killing the
> phone?  Has anyone seen anything like this before?
> 

Yes, we saw similar on a phone (though I can't recall which model, we
have 7912s and 7940s mostly) and it was down to a poor solder joint on
the ethernet switch pcb of the phone, some of the pins were connected so
the phone could source power but one of the ethernet pins was knackered.
We were able to get the phone working by wiggling the patch lead about
so it was quite obvious what it was from that, open it up and have a
look at that board though if you can't resolder it it might be a breaker
for spares now.

David.
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