Case Study: Ubiquiti Unifi PoE Switch US-8-150W Power Supply Failure and Repair

If you have a Ubiquiti US-8-150W switch, and it’s suddenly dead or unstable, it’s probably the power supply. In this post, you’re going to learn what causes these switches to stop working as well as a few different ways to repair them. This article focuses on the US-8-150W, although this info may apply to other Ubiquiti models as well.

The Problem with the US-8-150W

The US-8-150W uses the Gospower G0398-15011480A power supply. If you do a quick Bing or Google search, you’ll find multiple people online that found the same dead power supply in their dead US-8-150W. Some people have repaired them, finding various faults. Some of the power supplies died with a loud bang, burn marks on the PCBs, and obviously failed components, others looked perfectly fine from a quick visual inspection but simply didn’t work. Before we continue, a quick disclaimer: this article is for entertainment purposes only, and working on power supplies can be dangerous – I’m not responsive for anything that may go wrong.

The innards of our US-8-150W looked OK from a brief visual inspection. Using a multimeter, I tested the output of the power supply and found it to be fluctuating between 0 and 24V while still connected to the switch’s mainboard. Upon unplugging the output, it simply sat around 24V… definitely not useful when it’s supposed to be outputting a steady 53V!

Unfortunately, the G0398-15011480A doesn’t lend itself to easy repair. It has a single heatsink that covers about two thirds of the PSU (power supply unit). Anyway, once the heatsink was removed a closer visual inspection it was obvious the top of the primary capacitor, an “STGCON” 450v/150uF, was bulged. Removing the plastic covering made it easier to see and photograph.

Failed STGCON Capacitor from US-8-150W
Failed STGCON Capacitor from US-8-150W

Replacing that failed capacitor with a used Nippon Chemi-Con KXG 450V/100uF out of some other random dead PSU for testing purposes restored a steady 53V output – thankfully no other components on this power supply were damaged when the original cap died. The trouble is, it’s hard to source a trustworthy replacement capacitor with the same specs and dimensions. Something like this should work.

Solution 1: Fix the OEM PSU

If you can, fix the original power supply. It’s a bit tedious, but it’s the cheapest option. Hopefully you just need a single capacitor, and nothing else was taken out by the failed cap. If you need help, contact me and I may be able to offer an affordable repair if you ship me the power supply and/or switch.

Solution 2: Direct Replacement PSU

An easy, direct replacement power supply is available, although it was officially discontinued by the manufacturer in 2020, so it might be hard to find. The Mean-Well ASP-150-48 has the same dimensions, mounting holes, and connectors. While it’s only a 48V unit vs the original 53V unit, users have confirmed it works fine. At the time of this writing, you can purchase the Mean-Well ASP-150-48 on Amazon, but it’s a whopping $120. I found them online at other places too, priced similarly. Once the supply of these supplies dries up, there is no other known direct replacement available – Neither Ubiquiti nor Gospower offer them. If you find a good direct-fit alternative, please let me know in the comments section below.

Solution 3: Alternate Replacement PSU

Searching eBay and Amazon for “48v power supply” brings up a bunch of new and used power supplies that may or may not work. In theory, any 48V-53V DC power supply will work.

For my US-8-150W, I found a lightly used Cosel LEA50F-48-Y on eBay for like $10 shipped. It’s only rated for 50W, not 150W, but for my usage (only one PoE device) this is not a problem. I did have to rearrange the pins on the output connector and make my own mounts, and for safety I should have run a ground from the unused ground pin on the input connector, but it worked perfectly. The LEA50F-48-Y does have adjustable output, which is cool, so I set it to about 52V, but even if whatever unit you find is just 48V you should be OK.

DIY Replacement 48V PSU US-8-150W
DIY Replacement 48V PSU US-8-150W

Another option is to use an external power adapter and splice that into the wires from the 4-pin connector that goes into the mainboard of the switch. If you want to get fancy about it, drill a hole in the back of the switch, install a DC jack, and either leave the old/disconnected AC plug as a dummy or pry it out and cover it with something.

US-8-150W vs US-16-150W Power Supplies

If you’re lucky, you’ll end up with a dead US-16-150W as well, that died for some other reason. I acquired a US-16-150W that wasn’t working, although the power supply was just fine. Something more serious is wrong with that one – I’m still troubleshooting it. In the meantime, since they use interchangeable power supplies, I ended up using the much better designed power supply from the US-16-150W in the US-8-150W. As you can see, the design is far better – the heatsink is not covering the primary capacitor, and although CapXon is still a low-grade part, it’s better than STGCON.

US-8-150W with US-16-150W PSU
US-8-150W with US-16-150W PSU

So, what did Ubiquiti do wrong?

Obviously this is not an isolated issue – after all, you ended up on this article for a reason. While we’ll never know the true failure rate, it shouldn’t be this high and would have been very easily preventable.

First things first, the Gospower power supply is a bad design. It’s that simple. One large heatsink covering a subpar primary capacitor? Brilliant! /s.

Next up, the cooling on these switches is a joke. Fanless is OK for low-power consumer grade networking equipment but not for business-class equipment with PoE support.

On the US-8-150W, the addition of a couple fans would have made a huge difference. Sure, that cheap primary cap on the Gospower PSU would still get toasty, but it probably would have lasted 5+ years with no issues. If you want to add a fan or two to the US-8-150W, keep in mind you’ll need to also install a DC-to-DC converter to power them as 30mm or 35mm 48V DC fans aren’t readily available.

A note about the US-16-150W – that’s a dumb design too – and that’s why there are also plenty of reports of the 16-porter having power supply failures as well. It has two fans but they are nowhere near the power supply. Either relocating one of the existing fans nearer to the power supply or adding a third fan would have cost pennies.

I’d love to hear from you!

Have one of these with the same problem? Fixed it? Something else? Let us know in the comments below.

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