Fixing a Cisco 2500 with a dead power supply.

By | May 22, 2006

Ok, this one is from a long ways back but still relavent, we still use this router to this day ! You would be surpirised just how many 2500’s are still in service. A little addition to this story to come clean after all these years. My boss at the time was not too keen on trying this, he was justifiably scared of blasting away our one and only router, at this time this was probably the only 2500 in NC. Me, I knew it would work, but rather than have it go up in flmaes in front of him I tried it when he was not looking (sorry Al) and when it worked then went and talked him into to trying it knowing full well that it was going to work šŸ™‚ I am not quite sure what I was going to do if I fried the router, I guess it didn’t matter much as at that stage we didn’t really know if it was just the power supply.

I got quite a few other people who have done the same thing after reading this but they didn’t send photo’s, one was from some guy in the far north of Norway who was very grateful to get his only link with the outside world back up. Anyway, happy reading …

Updated 15/06/2021 to put photos back in here

What started out as a truly ordinary day soon turned into nightmare material when, while working over Christmas on the network we decided to power down our one and only Cisco 2550 for a few minutes. On power up there was a big bang and the smell of burnt out circuits. Damn, no Internet, no Email no nothing (no we don’t have a spare) !! What to do now, no one else was at work as we had come in on a holiday to do some testing. After a few frantic phone calls we found out we could get a power supply from Australia but this would take a few days unless we took the very expensive courier option.

dead csico power supply

Dead Cisco PSU

A closer inspection of the power supply revealed what seemed to a standard PC motherboard power connector, an even closer inspection revealed that Cisco were even kind enough to use standard colour coding. Although the colours were in different places and the power supply was dead I was fairly quickly able to deduce that the Black was ground, the red was +5v, the Yellow was +12v and the violet colour was -12V. The violet wire was the only deviation from the PC standard, this wire is BLUE on most power supplies. The voltages were fairly easy to work out as it was just a matter of chasing the tracks on the board back to the various regulators.

Cisco 2500 Power Supply Connector

Cisco 2500 Power Supply Connector

So next step was to get an old PC power supply and just rearrange the order of the wires on one of the connectors and plug it into the Cisco.

Front view - yep that's rust.

Front view – yep that’s rust.

Our router with supercharged outboard power supply ! Anyway, we ended up being off the air for only about 2 hours, the replacement didn’t get to use for about a week later, the Cisco ran quite happily on its new power supply for about 10 days in the end, this is what working in the Pacific is all about folks, it’s called appropriate technology, in other words use whatever you can to get the job done.


I get Emails about this page all the time, here’s some others who done the same thing based on what’s here šŸ™‚

Jon Leeman and Bill McDonald on Nauru

Jay, 19 years old from the US

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