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Old 11-22-2012, 10:08 PM   #1
shpitz461
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Default Netgear WNDR3700 Whining Sound

Hi everyone,

I got an issue with a WNDR3700 that recently started whining. I've read about the capacitors issue so I figured out that must be the problem.

I opened it up, and even though none of the capacitors seem to be bad, I still replaced them.

Back:

Front:

The caps I replaced are marked in Red.

I put my ear to the board, and i think the sound is coming from the area marked in green. I think it's under that silver protective cover.

Any idea how to remove that cover? what else can cause the whining sound?

Thanks!
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Old 11-22-2012, 10:22 PM   #2
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Default Re: Netgear WNDR3700 Whining Sound

You'd think Netgear would use decent caps on their top of the line $100+ router...

What did you use to replace them?

That silver cover is a shield. There's silver foil tape on the right side, and then there are what I would call tabs around the shield. It should be pretty easy to remove if you take your time. I'm pretty sure it's not soldered. I doubt you're going to find anything there.

Besides double-checking which caps you used to replace the stock caps, I suggest you take a good look at the AC Adapter...
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Old 11-22-2012, 11:24 PM   #3
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Default Re: Netgear WNDR3700 Whining Sound

Quote:
Originally Posted by mockingbird View Post
What did you use to replace them?
Thanks for the quick reply!

I've replaced them with the following:

Lelon 470uF 16V High Temp Radial Capacitor

Lelon 470uF 25V High Temp Radial Capacitor

I'm at a total loss as to where the fault is causing the whine sound.
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Old 11-23-2012, 01:08 AM   #4
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Default Re: Netgear WNDR3700 Whining Sound

From the fire into the frying pan...

Don't use Lelon caps. What were the originals? Also, did you crack open the Adapter?
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Old 11-23-2012, 08:51 AM   #5
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Default Re: Netgear WNDR3700 Whining Sound

I threw away the original caps, they had a light blue casing, and all I remember is that they had a 6-digit number, but no brand that I could see.

You think the A/C adapter might be causing this?
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Old 11-23-2012, 09:58 AM   #6
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Default Re: Netgear WNDR3700 Whining Sound

First I would put some high quality caps in there to eliminate the possibility of them being the problem.

Yes, the adapter could also be causing it.
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Old 11-23-2012, 11:07 AM   #7
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Default Re: Netgear WNDR3700 Whining Sound

Quote:
Originally Posted by mockingbird View Post
First I would put some high quality caps in there to eliminate the possibility of them being the problem.
Can you point me in the right direction?

I'll look into the A/C adapter as well.

Appreciate it!
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Old 11-23-2012, 02:56 PM   #8
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Default Re: Netgear WNDR3700 Whining Sound

Depends where you want to order from. See what caps the adapter needs, and then I can check which supplier has the best selection because those adapters often use caps which have odd sizes that are not universally stocked.
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Old 11-23-2012, 03:13 PM   #9
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Default Re: Netgear WNDR3700 Whining Sound

Sounds good, thanks!

I will check the A/C adapter tonight or tomorrow and get back to you.
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Old 11-23-2012, 09:47 PM   #10
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Default Re: Netgear WNDR3700 Whining Sound

I'm in the middle of recapping my WNDR3700 V1. It's a great router, works fine but the 2.4GHz RF range is poor, so I am also doing the quad external antenna mod. Many people report "radio death" on these routers which I'd guess are due to failing capacitors. I have good Lelons but swapping them out. Upgrading to OpenWRT (wiki with lots of info) firmware seems to change the power drain. Again, guessing the RF section regulators get unstable and weak caps cause it to whine.

Measured (router works):
C118 (12.2VDC IN) 470uf 25V; 10mmOD x H=17mm, 5mm/0.2" LS
C73 (5.26V RF) 470uf 16V; 8mm OD x H=16mm, 3.5mm LS
C276 (5.44V RF) 470uf 16V; 8mm OD x H=16mm, 3.5mm LS
C142 (1.23V CPU) 470uf 16V; 8mm OD x H=16mm, 3.5mm LS

I'm going with Nichicon long life HE series:
470uf 16V; 8mm OD x H=15mm, 3.5mm LS; UHE1C471MPD Digikey 493-1522ND $0.53 ea.
470uf 25V; 10mm ODx H=16mm, 5mm LS; UHE1E471MPD6 Digikey 493-1553ND $0.78 ea.

The AC adapter measures 12.2VDC with no load and under load, it's still working. I feltpenned the LED's- they were too bright.
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Old 11-24-2012, 09:42 AM   #11
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Default Re: Netgear WNDR3700 Whining Sound

If Lelon's quality were as good as their aggressive/tenacious marketing people they'd be world beaters. But their quality is not good enough for stressful applications. Nichicon HE series is good stuff - not the utterly lowest impedance, but still quite low, and tough enough for stressful applications. UCC's KZE series and Rubycon's ZL series are about the same performance and quality/life.

Lelonian (and others') crap may be cheap up front, but how much does flaky equipment performance and two years' shorter life cost (or POed customers)?
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Old 11-24-2012, 10:03 AM   #12
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Default Re: Netgear WNDR3700 Whining Sound

Addendum: even in commodity products, like much computer gear, brand familiarity/loyalty is highly significant in purchase decisions. If you save a few cents apiece by using crapacitors it adds up to big $$, BUT you have to sell a LOT of routers or computers or motherboards to make up for a few thousand highly POed former customers telling tens of thousands of friends not to buy XYZ Brand whatevers because their quality is terrible!
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Old 11-26-2012, 08:25 PM   #13
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Default Re: Netgear WNDR3700 Whining Sound

I'm struggling in opening the A/C adapter, can you show me how to open its case w/o breaking it? I don't see any screws holding it together, how do I separate the plastic cover?

Thanks
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Old 11-26-2012, 08:34 PM   #14
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Default Re: Netgear WNDR3700 Whining Sound

Dremel tool. Don't cut too deep.
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Old 11-26-2012, 08:59 PM   #15
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Default Re: Netgear WNDR3700 Whining Sound

Got it, used a utility knife for starters, then a flat screwdriver and a plastic prying tool to open it, was tough to do since it was glued pretty good.

I'm not seeing anything wrong with it:





But it smells pretty bad, I wonder if it's just defective and is what is causing the router whine, what do you think?

How can tell if the adapter is good? What should I check for? It is rated [email protected], I do have a digital DMM.

Thanks!
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Old 11-26-2012, 09:06 PM   #16
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Default Re: Netgear WNDR3700 Whining Sound

Quote:
Originally Posted by shpitz461 View Post
Got it, used a utility knife for starters, then a flat screwdriver and a plastic prying tool to open it, was tough to do since it was glued pretty good.

I'm not seeing anything wrong with it:





But it smells pretty bad, I wonder if it's just defective and is what is causing the router whine, what do you think?

How can tell if the adapter is good? What should I check for? It is rated [email protected], I do have a digital DMM.

Thanks!
It's typical for some of them to smell bad. The smell comes from the tape, glue, or plastic, etc...

Try replacing the output capacitors with a good brand.
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Old 11-26-2012, 09:07 PM   #17
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Default Re: Netgear WNDR3700 Whining Sound

You mean those two blue ones?

I also don't think the plates were connected that well to the transistors, they are held by a screw.

Last edited by shpitz461; 11-26-2012 at 09:11 PM..
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Old 11-26-2012, 09:08 PM   #18
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Default Re: Netgear WNDR3700 Whining Sound

Quote:
Originally Posted by shpitz461 View Post
You mean those two blue ones?
Yep!
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Old 11-26-2012, 10:03 PM   #19
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Default Re: Netgear WNDR3700 Whining Sound

Quote:
It's typical for some of them to smell bad. The smell comes from the tape, glue, or plastic, etc...
I disagree. I am familiar with the smell he's talking about. I think it's from electrolyte vapor reacting with some of the components in the sealed adapter. I know that smell from many adapters I've opened up with Chinese caps.

Change -ALL- the capacitors, including the primary cap... Small primary caps from unreliable brands should be treated the same as secondary caps. They don't typically last like the big off-brand input caps. Don't forget to change that small cap near the large input cap that's covered with silastic.

If you want to test it, put your multimeter on AC mA setting and see how much AC is leaking through.

Post the brand, diameter, series, and dimensions of each cap.
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Old 11-26-2012, 11:40 PM   #20
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Default Re: Netgear WNDR3700 Whining Sound

I would measure no-load voltage and then load test it, with something like a car taillight bulb, that's about 1.5A or use a big resistor.
What value are the two blue caps?
The soldering on the output inductor (donut) looks weak and I would touch them up.
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