Failing PA Paging Speakers and Adapters (PoE)

[shaakir]

Hi,

We have a fairly large (60+) [brand name excluded] PA speaker and adapter deployment connected almost exclusively to MS switches.

We're finding a number of them dropping off from time to time, requiring diode replacement to fix. The retailer and upstream are baffled as to why this is happening, as these appear to be rare (for them), and we are being asked what injectors we're using, any power issues, etc.

The vendor and reseller have been gracious about it and the reseller has been ordering parts and repairing them for no cost, despite some being out of warranty and so on. We don't expect this level of service, but are thankful for it.

We are using only line-interactive UPSes for the majority of our switches, and do have our share of power outages.

Any thoughts, shared experiences?

The MS225 data sheet, for example, makes no claim to any power conditioning, filtering, whatever, although we would've liked something to be mentioned (either way).

Thanks,
shaakir

[alemabrahao]

To be honest I don't think that it's a Meraki issue.

[shaakir]

Perhaps the vendor would beg to differ.

We're keeping out minds open: Could it be a ... power issue? That depends, in part, about how Meraki handles power. May be it doesn't do much, if the power is dirty?

Dunno. Nothing to go by, unless we start attaching power testing equipment with PoE ports and start screwing around with our AC.

[Brash]

Switches typically don't include any type of conditioning as part of their PoE output.
The PoE output is however typically isolated from the main input voltage.
If there was a surge/spike that impacted the PoE output, I would expect it to also damage components inside the switch.

It's not unheard of that switches can cook PoE devices but it's not particularly common in enterprise grade switches and enterprise grade PoE devices.
More commonly it's poorly built PoE devices or failing capacitors in them that end up breaking.

[cmr]

@shaakir PoE power delivery is usually about -48V DC and when a switch reboots, the PoE supply is shut off until the switch has rebooted and stabilised.  If you look at the port that one of the devices is connected to what does it show in terms of power drawn and power requested?

[shaakir]

With the latest device that bit the dust, the PoE symbol was there on the switch port, but no link light, and if my memory serves me correctly, minimal power consumption was metred. In this case, we don't yet know if it is a typical diode failure that was the issue with other devices from the same vendor, or something else. The third party device itself appeared to be completely dead. No lights, etc.

Could it be that other devices (or sub-standard cabling with other devices) might be causing issues? Such as a short? I've seen PoE switches being reverse-powered by PoE supply from another switch, despite that not being a documented capability that we could find. Pretty freaky but perhaps handy at times. I've seen these switches also not "take on" AC supplied-power (which would be DC anyway), and when in that state would have to be disconnected form their PoE surrogate to be "righted". I think this was a SG300-10. But in my mind, this behaviour is a sign of how "simplistic" these switches could be. I would expect switches like Meraki to be a lot more regulated.