WAN and LAN blinking router error

If you have a Broadcom-based router, most notably ASUS WL-500 and submodels, as well as numerous clones from D-Link, Buffalo, Linksys and some other, you may experience the following error.

All 5 front LEDs (WAN and 4 LAN port) constantly on simultaneously. The router is not accessible via neither wi-fi, nor ethernet.

Your first desire would be to put the router into recovery mode to reupload firmware and NVRAM. Alas, the router doesn’t respond to either of the unbricking methods.
Don’t give up just yet. The problem may lie somewhere you expect least: the power supply. Those tiny AC/DC adapters that come with phones and other telecommunication equipment are getting more and more powerful each day. The wireless router power supply is 5v 2.5A. But the small case just cannot disperse the heat it generates efficiently. That’s why an average power adapter life span is about 3 to 5 years of 24/7 operation.
So try to measure the output of the power supply. But don’t just plug the multimeter directly to the power jack: that will probably show everything is OK. You need to get some resistance in between, like a light bulb or a resistor. if the multimeter shows a huge drop in voltage, like 1V instead if 5V, your power adapter needs replacement. Get a power adapter of the same voltage (5V) and at least the same power (2.5A or more). Also check the polarity, even some manufacturers just cannot agree with industry standard.
If you still experiencing constant rebooting and resets to factory defaults, try cleaning the contacts of the router power socket. After that, reflash NVRAM or reconfigure the device manually, and enjoy your best router to date.

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