[cisco-voip] Strike 3 - Dead 7940G IP Phones - Update

[Micah Bennett]

This issue is making my head hurt.  

To Recap:

Back in August two phones died within a few days of each other on the
same network port.  Cisco thought we had a bad switch and they replaced
it.  There were no problems between Aug and Dec.

12-05-08 - Phone 1 Died - Internal Switch is dead - Phone replaced and
connection moved to different port on the user switch to see if problem
comes back.

12-15-08 - Phone 2 Died - Same symptoms as 12-05-08 and August 08.  I
opened a case with Cisco.  They had no idea either so we put together a
plan to try and isolate the issue to either the wiring in the office or
the PC since those things have stayed the same.  We installed a 3rd
phone but now the PC and phone are on a totally new office port across
the room from the old one and going to a totally different switch in the
data center.

12-17-08 - Phone 3 Died - Same symptoms - The only thing that is the
same now is the PC.  We replaced the NIC in the PC fearing that
something was feeding back through it and killing the phone.

12-23-08 - Phone 4 Died - Same symptoms - We had gone the longest time
in a while so that morning I closed the Cisco case since it appeared we
had isolated the issue to the NIC in the PC.  When this 4th phone died I
was more baffled than ever.  I proceeded to ask all my normal questions
to the users involved again and finally found that the phone only seemed
to die when the user was using a thermal printer that was on that PC.
We print Hunting and Fishing licenses for multiple states so we have a
few of these special thermal printers for that purpose.  The user
proceeded to tell me "yeah, it had reset a few times early in the week
while printing, but always came back up."  Anyway, the issue now pointed
to the printer that was hooked to that PC.  We decided to take a risk
(that it would not kill the data center switch) and plug the PC directly
into the network without a phone in line.  We put the phone on a totally
separate office/network port from the PC in hopes that we could at least
stop killing phones.  

12-30-08 - Well, that idea only worked for about a week.  Last night the
5th phone at that location died.  The phone was only setting beside the
printer but not inline with it or the PC.  The only thing we can figure
now is some type of EMI (from the printer) like James mentioned below.
All of the cables (network and power) for the printer, PC and Phone are
going down through the same hole in the desk.  I have heard of EMI
before, but this is the first time any of us have every seen it.  

Is there anyway to confirm this is the problem or test for it.  I may be
able to move the Printer away from the phone and see if that helps.

Any suggestions would be great, I am really tired of working on
this.....

Micah Bennett

-----Original Message-----
From: James Buchanan [mailto:jbuchanan at ctiusa.com] 
Sent: Friday, December 05, 2008 9:03 PM
To: Micah Bennett; cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] Strike 3 - Dead 7940G IP Phones

Hello,

This sounds like an issue with the drop itself, and frankly sounds
rather dangerous (like something that could electrocute an end user). I
would have the drop checked and recertified. Furthermore, I would check
to see if there is anything that is causing EMI on the drop. Also,
sometimes users run electric heaters under their desks and melt things.
I once had a user who melted the entire front of a brand-new PC.

Thanks,

James

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Micah Bennett
Sent: Friday, December 05, 2008 9:03 AM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] Strike 3 - Dead 7940G IP Phones

Well its been a few months since this issue happened to us.  Back in
July, Cisco ended up replacing the POE switch saying the issue was
probably a bad port there.  

Today, the new switch killed a third phone on the same port 12.  If I
plug a new phone in port 12 it works.  If I try the old one on port 12
or any other port, nothing - DEAD.

I find it hard to believe that this could be a problem in the POE switch
again on the same port.  I checked the third phone based off Davids
comments from back then.  I don't see any issues and moving the enet
cord does not help, but the phone switch sure smells like something
burned up.

These three phones are in a similar serial number range, but then again,
all of our phones are and this only happens at this network port.  

I am beginning to wonder if the NIC in the PC might be the problem and
its feeding back to they phone and smoking it.  

Any advice?

Thanks Micah.

----------------------------------------------------------

From: David Sullivan [mailto:David.Sullivan at barnet.ac.uk] 
Sent: Thursday, July 31, 2008 9:05 AM
To: Micah Bennett
Cc: cisco-voip at puck.nether.net
Subject: RE: [cisco-voip] Strike 2 - Dead 7940G IP Phones

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.

-----Original Message-----

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?	

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