ParkingLotLust

If you search my recent posts, youll see I have a buzzing WRT54G. The power brick is whats doing the buzzing. I discovered that if I removed the PWM chip, it stopped. I purchased a replacement and installed it, and now it still buzzes. This leads me to believe the other chip might have been bad. Since I have no freakin' clue whats wrong with it, Im left replacing chips until it works again. Anyways, I need an equivalent to a chip with the following markings. I google'd it and couldnt find any matches in terms of the markings.

9936
31B9M

It is an 8-pin SOIC chip, located right at the power input. I can try and get a close-up picture of the location of the chip if it will help.

justDIY

the wrt54g contains an onboard buck converter, I believe accepting up to 20v and down to 5v, the unit itself running on 3.3v.

have you tried using other power bricks, to see if they have the same problem?

my wrt54g (all three of them) came with heavy unregulated "12vdc" power supplies ... the heft implying a simple transformer + rectifier + cap configuration, leaving the regulation to the chip onboard the wrt

in the field I run my wrt off a parallel bank of 6v gel-cells which fit nicely in a small camera bag, but have also run it straight off "12 volt" power from my truck and a 12v deep-cycle battery, it's a pretty flexible chip

all that being said, if there were something wrong with the chip, it would either not work at all, get terribly hot, smoke something else in the router or all of the above. has any of these symptoms occurred?

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ParkingLotLust

I replaced the synchronous buck pwm controller chip. That was my first guess since it would handle the incoming power, but that didnt fix it. I bought it for $20 off eBay, as being broken, as something to play around with.

Its running off the power brick that came with it. I have a v5 running dd-wrt but theyre a different voltage brick, so I dont want to hurt it. I believe the one I have is a v1 or a v2 (with the mini-pci card on the wrt54g board). Anything else I can try before I start replacing more chips?

mvs sarma

Hi,

whether the buzz (if it is audible) is not due to transformer packing being loose and the coil former sitting loose on the Ferrite core and things like this--

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ParkingLotLust

So what should I do to fix it? I dont quite understand what you're saying.

Oznog

Also a bad output or input cap can cause instability that can make audible buzzing.

If the supply has a prob causing terrible ripple, that can cause a similar instability prob.

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ParkingLotLust

So try replacing the big electrolytics by the input jack aswell? Ill try another power brick too if I can get my hands on one of the same rating

Nigel Goodwin

To be honest, I would have thought the least likely cause is going to be a faulty IC - as suggested FAR more likely is the transformer mechanically noisey, or a faulty capacitor.

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ParkingLotLust

Will it do any damage to remove a capacitor and test?

Nigel Goodwin

Presumably you mean test the PSU without the capacitor fitted?, depending on the capacitor it might well do LOT'S of damage.

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ParkingLotLust

Hmm which caps are we talking about, that could be bad? the ones in the power brick, or the ones on the board of the router?

justDIY

whichever electrolytics there are, replace 'em both, they're cheap!

I see two on my wrt54g rev 1

Attached Images

wrt54g-switcher1.jpg (317.8 KB, 13 views)

__________________
If you don't have a planet, what good are gold bars?

want to contact me directly? gmail gordonthree
check out my project website: http://projects.dimension-x.net
Favorite numbers:
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

ParkingLotLust

My board looks more like this. Which caps should I be replacing? The big pair, or the small pair?

http://seattlewireless.net/~mattw/ph...e/IMG_3425.JPG

justDIY

oh, that's not your board ... but if yours look like that, with no visual signs of distress, I'd be highly suspect of anything being wrong with the caps.

if you still want to replace any, replace all four, two big ones and two little ones.

__________________
If you don't have a planet, what good are gold bars?

want to contact me directly? gmail gordonthree
check out my project website: http://projects.dimension-x.net
Favorite numbers:
09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0

ParkingLotLust

Thats exactly what my board looks like. No visual signs of wear or anything. Thats why I suspected the chip, because when I removed it the buzzing stopped, but it obviously still doesnt work.