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Totally dead router after possible power surge

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xieliwei

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Hello all,

I've got (another) router which broke down years ago due to a possible power surge (gee, I must really consider getting a surge protector). In this case, the result is quite severe (yet interesting).

Firstly, the wall wart (5V2A) seems to be working fine (unconfirmed, reason for that later), as it produces a nice ~5.1V when unconnected.

Secondly, when plugged in, the potential between both poles of the wall wart drops to about 1.5V.

Thirdly, almost all of the capacitors (even those probably not associated with the power supply) have near 0 (0.4Ohm!) resistance. Those that do not have near 0 resistance show an increasing resistance up to about 20kOhm, then starts to drop slowly.

Fourth, the polyfuse F1 does not seem to heat up nor cut off when the wall wart is connected and turned on.

Fifth, nothing heats up.

Sixth, my test light lights up with respect to me. I experience a shock when touching the case of the router, which a quick check has shown is directly wired to the negative power terminal.

Seventh, there are two voltage regulators on board, both do not seem to do anything (more on that later).

The interesting thing is that no matter which component and where I test, the potential is always 1.5V with respect to ground. Thus one of the voltage regulators (VR1), rated for 3.3V output, shows 1.5V. That should be normal, since 1.5V is lower than 3.3V.

However...

When I plug my generic wall wart in, things are the same, potential drops to about 1.5V and can be measured at almost any point in the circuit. But if I plug the connector in half way (connector problem?), I get an approximately 5.1V difference between both poles of the wall wart. Furthermore, this 5.1V can be measured throughout the circuit as well (similar to before, just that its 5.1V now). Even the Vout of both voltage regulators show 5.1V.

I suspect that there is some nasty short somewhere, but where? Visual inspection shows no physical short, nor are any capacitors relatively or significantly bulging.

Can someone help? Very appreciated! :)

Attached are front and back pictures of the circuit board:
http://www.rvnet.ath.cx/xieliwei/router/DSC04825.JPG
http://www.rvnet.ath.cx/xieliwei/router/DSC04826.JPG
 
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