Trying To Fix A Suspiciously Cheap Enterprise-Grade Network Switch

When you see a listing for an Ethernet switch whose specification list is in effect ‘yes’, with a four-digit price tag when new, and with the seller asking for less than 10% of said $3,000 asking price in an ‘untested’ condition, the only rational thing to do is of course to mash that ‘buy’ button. This is what [This Does Not Compute] did, and created a video about to show what a great investment decision this was.

Naturally this Juniper EX4100-F-12P switch came without power supply brick for its 48VDC input. Figuring out its pin-out and probing said input showed that the voltage rails had been shorted, giving a first clue as to why this switch had been on sale for so very cheap. Bravely hoping that it would be a straightforward fix, the unit was disassembled.

With a 280 Watt power brick, it’s little wonder that the top of the unit is a one massive aluminium heatsink, including a large heatpipe. Also visible on the lid near the power input was a very-bad-news black skid mark.

From that first discovery the news just got worse and worse, with clear signs of water ingression, rust and corrosion, along with the aftermath of a powered circuit meeting such bad corrosion. After some clean-up it’s clear that some components had violently exploded, ripping apart layers of the PCB and likely parts of traces in those inner sections too.

With no schematics available and no other good repair options via Juniper or anywhere else, it seems that unfortunately this gamble turned out to be merely a pile of e-waste and a few bucks worth of scrap metal. Caveat emptor, once more.

20 thoughts on “Trying To Fix A Suspiciously Cheap Enterprise-Grade Network Switch”

  1. Really don’t see why promoting this is particularly beneficial.

    Sure, there’s value in failures. (Pure success doesn’t teach much. But there’s plenty of failures available if you want to study them.

    1. It’s a useful reminder that the phrase “untested” one eBay actually means “tested, broken, sold by a con artist”. Selling without the power supply, or more lamely without a standard power lead, is often the excuse for it being untested. Later you’ll find them selling the power supply.

      1. Indeed, if I see something listed as “untested” my brain automatically reads it as “definitely tested and totally not working”. If I’m curious, I’ll check what other items (past and present) the seller has, e.g. I’ve seen a seller having the same consoles, one “working” and one “untested”, and someone selling untested “because I don’t have the PSU” and the PSU listed as another item.

        1. I did buy an “untested” serial data generator for cheap. It was totally dead, not even a power light, so I immediately thought “power supply”, and set about looking to repair it. Then my brain kicked in and I started unplugging cables. Unplugging the front panel brought it to life. A little poking around identified a shorted cap on the 5V supply rail.

          Replacing the cap brought the power supply back up (good design!) but I had already ordered a replacement. I ended up replacing it anyway because it was a 1990s design and I figured a modern supply would be smaller and probably better designed with modern parts.

          I knew what I was getting into in this case, but, like you, I view eBay with great skepticism.

  2. Not sure why this switch would be worth 4 digits. I have 48 port POE switches from HP that were $50 and are quite capable (and not water damaged)

    1. Junipers are worth their money, but only in a corporate environment and with a service contract. Also project prices are well below list prices.

  3. Agree that ex-commercial gear is the way to go, but $300 for a 12 port gigabit switch, even with POE+ is a bit much. I have several HP/Aruba 48 port managed gigabit switches with POE(not + though) that I have paid $50 for. They are reliable, versatile and plentiful on the used market. Unless you need extreme performance, there are a LOT of switches out there for cheap, even on Goodwill!

  4. Did y’all miss out on the Brocade ICX 6610-48P-E switches? Used to be $20K-ish switches ~10 years ago. 48 ports of 1 Gb PoE, dual redundant power supplies, 8x SFP+ 10 Gb ports, 2x 40Gb uplink ports, managed. And a very nice guy who gives away an unlock-everything license for home-labbers upcycling old hardware. Got my 2nd one for $95, first was $200-ish. Fully tested. Couple that with some upcycled HP 40Gb Fibre Channel cards reflashed to be 40GbE, got some killer network speed there. Or one heckuva bargain on massive PoE capacity, 48 ports for less than a new 8-port.

    1. I’m currently learning about setting up my own NAS w a bunch of storage for my musician husband & I to utilize on our 1-2gb speed internet, it’s a lot of info but any pointers on finding a useful score like your brocade switch would be really appreciated! So far I have saved searches set up but it gets a little overwhelming sorting through the specs! Thank you!

  5. He should watch when NorthWest Repair takes a rotary grinding bit to a GPU PCB and digs out burned or cracked layers, then rewires the inner layers one by one. Probably doing it for a power supply section would be much easier.

  6. Found a ex3400-48p in the e waste bin, took it home and it just needed a firmware reflash. Firmware isn’t the easiest thing to find if you don’t have a service plan from juniper, but it’s running just fine now!

  7. This reminds me of something similar i did a while back. My brother found an old bluetooth speaker magnet fishing in the bottom of the lake, and I offered to try and fix it for him. I knew it would never be as good as the original, but I was still able to replace all of the electrolytic capacitors and inductors with parts I had lying around (the originals had corroded off), remove the trashed lithium ion battery, power it up on the bench supply, and play music on it. It sounded terrible and its standby current consumption was 48 mA (lol) but it was still hilarious to listen to a speaker that had been underwater for years play music.

    IDK about that switch though, that board looks pretty toast. You win some, you lose some.

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