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Unifi US-8-150w PoE ‘chip’ roasted?

[ Edited ]

Hello Guys,

 

I am a UBNT fanatic with @home an USG-Pro, US-24-250w, US-8-150w (on the other side of the house powering other equipment) and serveral AP-AC-PRO’s! Works great. 

 

See here my home-setup for the record (FYI, the Cisco is VDSL2 bridge to the WAN port on the USG-Pro and IGMP Proxy for IPTV):

 

70996E83-CB3A-4CEB-83A9-6BB595A8D0F3.jpeg

 

However, last night my US-8-150w failed it’s PoE functionality on interfaces 3 and 4 and smoke was coming out of it! After i pulled the power cable i took a screwdriver to have a look on the inside, this is what i found out:

 

C4005709-BDA4-4962-AA7D-A4EA33A3FD84.jpegF5385A2F-69A7-454C-A0B3-F60D5FC50C7E.jpeg

 

As you guys can see, this (think this it’s for PoE) ‘chip’ has being fried for some reason.. 

unfortunately I dont’t have guarantee anymore since the switch has been over 2 years old but I found it rediculous that such an expensive switch can’t last for a couple of years.

 

But do you guys think it is safe to keep using the switch besides ports 3 and 4? All the other interfaces are working fine, including PoE. On the other hand i am not thrilled of keeping this device up and running since it’s an 24/7 device... thoughts?

 

Regards, MM

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Re: Unifi US-8-150w PoE ‘chip’ roasted?

I'd say the safe answer is, 'I don't have a clue'. I don't know

what the failure mechanism was or what got damaged, so I

don't know if this could extend to other ports or could make

the switch susceptible of more smoke and fire.

 

Because of that, I would not continue to use this switch.

 

It's not common for these switches to fail so soon. This sort of

damage is more typically caused by an external surge--such

as a passing thunderstorm.   Dave


> HQ in Seacoast region New Hampshire U.S.A.
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Re: Unifi US-8-150w PoE ‘chip’ roasted?

[ Edited ]

Those traces connect to the M-Tec ethernet transformer module ( the large chip looking thing - it's not a "chip" in the normal sense at all as there are no active devices inside) and burning a trace on the board is bad.   It usually means that the device connected to that port somehow back-fed power into the port - there are PTC fuses on the PoE inputs to the  transformers that will keep the power out from exceeding what the units are designed for - 500ma in this case.   And that's nowhere near enough power to fry traces on the board like in your picture.  It's theoretically possible for a PTC fuse to fail, but I've never seen one do that in my 40+ years in the business.    What exactly was plugged into those ports?   I would also check the ethernet cabling to those ports to make sure a cable didn't fray or short to something causing this.

 

So I would look at whatever was plugged into those ports - it may well be the culprit here, not the switch itself.   If some type of power got onto the ground (negative voltage) line of the device it could well have fed power back into the switch and the PTC fuses wouldn't limit ground current.

 

On your other question, yes there should be no problem using the remaining working ports, unless the devices there also fail.   I really don't think this was a switch problem...

Jim

" How can anyone trust Scientists? If new evidence comes along, they change their minds! " Politician's joke (sort of...)
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Re: Unifi US-8-150w PoE ‘chip’ roasted?

[ Edited ]

That's a fine analysis, Jim. But I don't quite understand how

you square '...it could well have fed power back into the switch

and the PC fuses wouldn't limit ground current' with the other

comment: '...there should be no problem using the remaining

working ports..."

 

If unlimited power could have been fed back into the switch,

isn't there a reasonable chance for undiscovered damage

that could result in improper operation?    Dave


> HQ in Seacoast region New Hampshire U.S.A.
> Ubiquiti Certified Trainer [UCT] for:
     UBWA [AirMax] / UEWA [UniFi] / UBRSS [routers]
UBNT.NH@gmail.com