Electronics > Repair

Unifi POE 24 switch, dead ethernet ports

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Krieger:
Hi all,

I just purchased a "non-working" Unifi 24 port POE network switch. Some of the ports on it work, some of the other ports are dead. They data light on the port stays a solid green. I disassembled the switch and did not see any burned traces or burned components. It appears that the POE portion of the ports work, it's just the data connection that is not working. I'm not familiar with repairing networking gear, and I was wondering if anybody could give me any pointers on what I should look at, or where I should start troubleshooting. I can post pictures (I'm assuming that will help).

From my initial teardown, it seems that there is a daughterboard for power delivery, and the main networking components are on the mainboard. I also have a non POE version of the switch is that would help in troubleshooting at all.

Thank you

asis:
Hi,
What is missing on RJ45 connectors - 48V or LAN (Ethernet)?
Photo is needed.

Whales:
Ethernet is missing.

I'm not certain, but I suspect 24 port gigabit switches might use a tree hierarchy of multiple switch chips?  Eg lots of 5-port or 8-port gigabit ethernet switch chips, then a layer more above those?  See if the non-working ports form a distinct pattern of (eg) 4 non-working ports.

EDIT: Also check the switch configuration if it's a managed switch!  Those ports might be software disabled or otherwise forced into unusable link modes.

Monkeh:

--- Quote from: Whales on August 14, 2022, 11:30:36 am ---I'm not certain, but I suspect 24 port gigabit switches might use a tree hierarchy of multiple switch chips?  Eg lots of 5-port or 8-port gigabit ethernet switch chips, then a layer more above those?  See if the non-working ports form a distinct pattern of (eg) 4 non-working ports.

--- End quote ---

You'd think, but no, that would introduce arbitrary bandwidth restrictions between port groups. It will have one colossal SoC with pretty much everything but 10Gb uplinks integrated. If there's a failure past the magnetics, it's not repairable - unless of course you have a line on replacement SoCs and the tooling to successfully replace a ~1000 ball BGA.

I would verify the integrity of each transformer and if they're good, scrap it or forget the ports exist. After, of course, verifying the switch isn't misconfigured.

Krieger:

--- Quote from: Whales on August 14, 2022, 11:30:36 am ---Ethernet is missing.

I'm not certain, but I suspect 24 port gigabit switches might use a tree hierarchy of multiple switch chips?  Eg lots of 5-port or 8-port gigabit ethernet switch chips, then a layer more above those?  See if the non-working ports form a distinct pattern of (eg) 4 non-working ports.

EDIT: Also check the switch configuration if it's a managed switch!  Those ports might be software disabled or otherwise forced into unusable link modes.

--- End quote ---

So, I'm not sure what the "switching" chips are that you speak of. Here is a video of a teardown of a similar switch (I have the POE version of this switch, but they are almost identical). https://youtu.be/bnyCDTA6sME?t=221. I was thinking that it could possibly be the g48209sng chip that is bad. The switch is a managed switch, it was factory reset. Currently, there are 6 dead ports, possibly more that are on their way out. There is a block of 4 ports, and then 2 ports that are not near each other. Seeing as there are 12 chips, it would make sense for blocks of 2 ports to go bad.

The ports with red plugs are dead. They get POE, no data connection.

For what it's worth, when I was testing the ports, some other ports acted odd, only getting 100FDX instead of the full gigabit connection. I went back and tested them again, and now some of those ports that were acting oddly are now working at 1000mbps, so it could be a SOC issue. I'm not sure.

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