05.12.2020

Power Supply for Asus Router

This is not the first time after a voltage drop in the network "burns" router WL-500g Premium. Symptoms are always the same – almost all LAN, WAN LEDs are lit on the front panel at the same time, AIR and POWER are barely lit – not lit. Reboot, reset did not help. For a long time, it seemed to me that this router can not be restored, the chip is supposedly broken.

What was my surprise when I "burnt" By chance, I picked up a power supply from another one to the router. The router has earned. So, the problem was precisely in the power supply, and not in the router itself. Long before that, I hooked up power supplies from D-Link, Asus – with them, he did not even start blinking LEDs.

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He connected the old power supply to the network, measured voltage – 5, 18 volts, which corresponds to the norm. By connecting a 5-ohm load resistor and repeating the measurements, I received an output voltage of 1 volt, which, of course, is very small – the voltage specifically sagged.

Disassembly

He carefully dismantled the power supply case with a knife, since it was weakly glued. An external examination revealed a malfunction – a bloated electrolytic capacitor in the output circuit of the power supply unit with a nominal value of 1200 μF x 10 V (in the figure under number 2).

Repairs

Having rummaged in old power supplies from a personal computer, a replacement candidate was quickly found – in the output circuit of the PWM controller there were several oxide capacitors with a nominal value of 1000 μF x 16 V.

When replacing the swollen capacitor with the voltage obtained from the power supply of the old computer, the voltage stopped sagging. Having connected the unit to the router, I found that the device worked fine.

Somewhere in a week another glitch was discovered – the power supply began to start from the tenth time. Having rummaged in detail in the circuit, it became clear that the blame was on the capacitor 47 uF x 25 V (in the figure under number 1). After replacing it with a capacitor with a nominal value of 10 μF x 50 V, the power supply began to start normally and almost stopped warming.

Completion

In order for the power supply to last longer, I recommend installing a ceramic with a nominal value of 10-100 nF in parallel with the electrolytic capacitor (I set 10) in order to bypass high-frequency interference (according to the advice of our grandfathers).

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