Can anyone throw in some thoughts on this?
Alarm panel with an Ethernet connection to a Cisco switch. The alarm panel goes offline. I see the board is charred near the Ethernet RJ45. The circuitry looks like this:
RJ45 ----> TVS diodes ----> Isolation transformer ----> Controller
The TVS diodes are blown off the board and the board is charred around them with blackened PCB. This would tell me the switch it was plugged into had a spike? The switch is plugged into a UPS though. A very expensive one. The PoE configuration on the switch is set to "never" so there should not have been 48 volts applied to the port ever.
Why would they protect an isolation transformer with TVS diodes? The panel manual says to not allow PoE or the TVS diodes could be damaged. The switch has not been touched for years. What would cause this to happen? Any ideas? Something catastrophic happened, any thoughts would be helpful. Thanks!
Could a switch go haywire and cause this? There were no storms in the area, for those who think it may have been lighting. Mystery....