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Hi, more a question of clarification than anything. I've just tested a TSW100, it's supposed to be 802.3af/at. It is my (no doubt deficient) understanding that the PoE device has a handshake that qualifies it to receive PoE. i.e. Plug in a passive PoE device and you won't get voltage on the cable? It seems I've popped a diode on a new Ubiquiti NBE-5AC-Gen2 (24V passive) by plugging it into the TSW100.

So, can someone please clarify what's happening here? I can plug the NanoBeam into a different 802.3af switch and not leave it useless, but the TSW100 has killed it due to my negligence.

Cheers.

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Hi,

I believe you had to receive POE Injector along with your Ubiquiti device? It is required to convert Active PoE to Passive PoE. If the device that you're trying to power does not say that it supports 802.03af/at - it will not, and I had some reading done on the datasheet of NBE-5AC and it says that it's only Passive PoE.

EB.
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Hi, thanks I know NanoBeams are passive, and because of that it should not receive power from an 802.3af/at enabled port in my understanding. This device did receive power and has therefore popped its TVS diode. Why is the TSW100 sending voltage to a passive device?
by

Hi,

I had a talk with RnD and it seems that the first revision and second revision of TSW100 devices have a difference that could've been a cause of your device being burned.

But first, we have some questions.

  • Did you use the cable with a shield? They look something like this:
  • Could it be that the housings of two devices somehow touched?
  • There's also a small chance that PoE transistor got shortened and GND was still intact, if that would be the case, RnD would like to ask you to send TSW100 to us for inspection.
EB.
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Good day. Thank you for the reply and your effort. 

The TSW100 is labelled from "Batch no: 005"

  • It is highly possible I used a shielded patch cable but I cannot confirm, I use a mix at my desk.
  • There is no chance the housings touched directly. I would have to force the corner of the switch into the plastic port cavity of the NanoBeam for that to occur.

The device that got popped was a new model NBE-5AC-Gen2. I also tested a deprecated unit (loco M5), instead of popping it just blinked all leds repeatedly (power/short issue indicator I think), but on normal power it's fine. I assume it has a less sensitive TVS diode.

If you still want the device inspected please let me know and I'll arrange it through our vendor (we have 3x TSW100 units delivered from the same vendor for the same client, not yet deployed). 

by

Hi,

Thank you for this helpful information, but I will need more testing done from you.

Could you check with the multimeter if there's continuity between GND and shield of RJ45 on your NBE-5AC-Gen2?

From this teardown image, it looks like there is, but we're not sure. It looks like the RJ45 shield is soldered into GND polygon, but that red filling doesn't allow us to confirm this.

EB.