Netgear WNDR4000 no power

[Dukenukemx]

One day I find the router dead. No lights or anything. One of the LEDS do blink but it's so quick it's hard to see. Checked the power supply and it puts out 12v, which is what the router needs. So naturally I check the caps by removing them and testing them. The only capacitors that seems a little off was a 330 that reads as a 303. That's border 10%, but I'm not sure if that's the cause of my problem at all? BTW, Lelon caps.

Tested all the caps to see their voltage and the two red circles in the image get 12v. The rest get nearly nothing. Like .5v or maybe 1.5v. Some get no power. So I'm assuming that the yellow things I circled are bad. I think they're voltage regulators or power regulators of some kind? Can anyone help confirm for me? I want to be able to test them but I have no idea what to look for.

[mariushm]

Re: Netgear WNDR4000 no power

Those are switching regulators (buck most likely).

Also, they probably won't work properly without those capacitors on the board.

No, 303uF is not good. Yes, capacitors have a 10% tolerance but any decent capacitor should be very close to the actual value, not that far away.
Put some low esr capacitors there, at least the capacitance that was before, you can go a bit higher.

Anyway, capacitance doesn't say much anyway. Capacitors could have high esr but show close enough value.

Use your continuity option on the multimeter to find a ground (I think one of the sides of that small ceramic capacitor in the top corner should be ground). Put a probe on the negative hole of a capacitor and the other on the ceramic cap sides, if it beeps you found the ground.

With the capacitors (new, or old ones) soldered back on the board, power the board and measure the voltage on the inductor leads (the big square things with 100 or 4R7 on them ) - put the black probe on ground you determined before and the red probe on the metal tabs on the sides of those inductors.

That should tell you if those switchers work. If you want/can, reply here with the measurements.

[Dukenukemx]

Re: Netgear WNDR4000 no power

I did what you said. Put the caps back in and found a ground. Bottom of those ceramic capacitors have ground. The top most 100 inductor lead has 5.25 volts. The second one bellow it gets nothing. The left most 4R7 gets .5 volts. The right most 4R7 gets nothing.

The 330uF capacitor is the one that is at the very top left of the board, near the power plug. I got to get a ESR tester.

[Dukenukemx]

Re: Netgear WNDR4000 no power

Any idea if any of this information means the switching regulators are bad, or possibly just the 330uF capacitor? I went ahead and ordered one of those cheap ESR testers off Ebay as well as a new 330uF capacitor.

[mariushm]

Re: Netgear WNDR4000 no power

The voltage on the first inductor tells you that the switching regulator associated with it works - that regulator takes whatever comes into the router ( you probably have a 12v 2.5A adapter according to manual) and outputs 5v.
From there, either another switching regulator is faulty, or something draws so much current that the switching regulators after it enter in some sort of current limit/overload mode.
I would replace the capacitor closest to this known working regulator with a proper capacitor and then I'd check for shorts between output pin of those regulators and ground, and check those tiny ceramic capacitors and resistors to see if one of them is shorted or broken (resistors can break and then there's open circuit there)

If there was some overload, the switching regulators would be very hot. If the chip isn't working at all, it should be cold to touch.

There should be some text on those chips, you can google that text and you should easily find the datasheet for those switching regulators and then look at a typical circuit with those chips. Even if the way the chip is used in the router doesn't look like the one in the datasheet, you know the pinout of the chip in the datasheet and then you can see if the chip receives some voltage (Vin and Ground, measure voltage) and you can check of the chip outputs some voltage.

[Dukenukemx]

Re: Netgear WNDR4000 no power

Tested the first two switching regulators. The two top left ones are MP1484EN. I tested the IN GRN and SW. Both left capacitors feed 12v into IN. Top one produces 5.25V from SW. The one bellow it does not produce any.

If I'm right, they use a 100k resistor to flip on the regulator through EN. The 5.25v regulator gets nearly 5.27 to EN. The 0v regulator also gets 5.4v in to EN. None of them are getting warm either.

Does that mean that one of the switching regulators are bad? I tested the resistors around them, and they all seem to be within each other. Didn't test the ceramic capacitors cause I think I need to remove them to test them, and they're a pain to deal with.

[shovenose]

Re: Netgear WNDR4000 no power

Have you tried a different power adapter?

[Dukenukemx]

Re: Netgear WNDR4000 no power

No I haven't but it does put out over 12v. I'll see if I have a similar adapter lying around to test with. My main concern is that switching regulator that doesn't output power. It gets the same power as the other, but doesn't output any power. I just need to make sure it's being properly turned on. I also need to get around to testing those ceramic capacitors. Hopefully without removing them.

[shovenose]

Re: Netgear WNDR4000 no power

Always the simplest solutions that are the hardest to find. It's probably dumb but try another PSU!

[Dukenukemx]

Re: Netgear WNDR4000 no power

The best match I could find is a 12v 2amp adapter. Plug it in and nothing changes.

[Dukenukemx]

Re: Netgear WNDR4000 no power

Got the 330uF Rubycon caps that I ordered from Ebay already. Seller gave me 7 of them for $5. Only needed 1 but can't have too many caps lying around. Already swapped it out and nothing changed. I ordered a new switching regulator and will swap it out and see how that works out. It's from China so that's going to take a while.

[Dukenukemx]

Re: Netgear WNDR4000 no power

ESR tester came in and tested that old 330uF. Shows 339uF with esr=0.3. The new Rubycon is 350uF with esr=0.2. Tomorrow I should get the regulator.