Question about replacement of the WLAN Hardware in Asus RT-N66U

Greetings friends.

I own Asus RT-N66U. Recently it has broken down and I'm going to give it in for repairs.
Today I had an idea and I want to know from you whether it is possible to implement it.
The idea is to replace the Broadcom BCM4331 chip to another one - with full Lede's support.
The question arises whether it is possible to compile the firmware for my router with the new chip.

Or is it better to buy a new router? :slight_smile:

I apologize for my English and
Thanks in advance for answers.

You may not need a custom firmware.

You probably can install the correct driver after flashing the router.

That's probably easier.


If you have to ask, you won't be able to do it. A BGA can't be replaced with a 5 bucks soldering iron, nor would you be able to supply/ generate new calibration data.


I have a familiar master with a professional soldering station, chip replacement is not a problem. I'm interested in the order of actions to make it work.

That still doesn't make it anymore practical.

Let's look at it this way, assume you'd get your device back into perfect working order...
Thanks to this very same wlan chip (BCM4331 for both radios), the Asus RT-N66U is among the worst choices for running LEDE/ OpenWrt in the first place (only very, very basic wlan support via b43, up to 54 MBit/s at best, no other alternatives, no hope for future improvements).

Even ignoring that using wlan on this router with LEDE isn't very reasonable to start with, in terms of features, performance and capabilities, the Asus RT-N66u is very similar to the TP-Link TL-WDR3600 (which is supported perfectly by LEDE) - which sold for ~45 EUR (new in stores, including 19% VAT) during the majority of its lifetime, defining the upper ceiling for your endeavour to be economically feasible. Another, current, example (with much better performance and good LEDE compatibility) would be the Xiaomi Mi Router 3G shipping for roughly 30-40 USD from China - and that's before even looking at the used market, which has quite some amazing devices to offer in the 5-10 EUR range (plus another 5-10 EUR shipping).
In other words, the upper limit to spend on your exercise would be somewhere between 30 USD and 45 EUR - because that amount of money would provide you with a brand-spanking new router with better performance and which is actually fully supported by LEDE right now.

If you'd already have access to the required infrastructure to solder and reball BGA chips -and had the experience to actually get that done yourself- you might be in a position to put it down as a learning experience to hunt down a replacement BGA (which might entail buying a working mini-PCIe card and salvaging the chip from that (careful, there are different variants of the BCM4331), as these chips aren't really available to consumer nor still being produced(?!), 10-25 EUR to be expected - maybe you're lucky to find the bare chip on offer somewhere in china, but given that you won't buy in bulk, the price would be around 7-10 USD per chip as well) and to just try it.
Even assuming you'd be able to get this sorted, that still won't help you with matching it against the existing rf components on the router board (no, Broadcom won't provide you datasheets, unless you order something like 500'000 and promise the same for next month), nor would it help you to generate the necessary calibration data (you just need a shielded high frequency lab (6-figure range and up), someone who actually knows what they're doing and, again, the necessary datasheets and calibration tools (available from Broadcom under NDA, if you buy enough chips per month to be considered worth talking to).

So under ideal circumstances, you're up to 20 USD for the bare chips in a quantity of 2 (1-6 weeks shipping time), 6 USD for the six-pack of beer you're compensating your "familiar master with a professional soldering station" to spend somewhere between 1 and 3 hours of their time to do the mere soldering job - plus a couple of millions for the privilege of getting answers from Broadcom and several shipping containers of bulk chips as a result of that incoming for the next couple of months. All for the warm fuzzy feeling of paying more than half of the new price of your router (respectively an equivalent one that actually works and in contrast is supported by LEDE) for the unfounded hope of possibly fixing it.

There is a reason why the ESP8266, the AMPAK AP6212 or the various SDIO based wlan modules from RealTek are so popular -especially for low(er) volume production-, dealing with 2.4 GHz or 5 GHz hf signals is difficult, even before thinking about the certification aspect.

There is no 1-2-3 step guide for beginners to get this done - and if you don't have free access to the necessary equipment plus the knowledge to try it yourself on a rainy evening, it doesn't make sense either - as you're paying more for an unclear result than buying a new replacement.

Replacing a SOIC8 flash chip might be feasible for a determined amateur, soldering on the missing USB ports, adding a SMD resistor to fix the deliberately broken serial port, maybe even replacing the RAM modules might be possible - replacing the SOC CPU or BGA wlan chips usually is not, at least not for mere mortals.

EDIT: all of this assumes that you try to replace the BCM4331 chip with an identical working one (assuming the BCM4331 is even the culprit in the first place), a chip that isn't really supported by LEDE either way. Dropping in a different wlan chip (from another manufacturer, or even the same) is impossible<period>. The pinout of these chips doesn't follow any standard, they need multiple assisting chips (flash, PHY, amps, band filters, etc.), changing this to another would require replacing the whole PCB (and re-routing the traces) and roughly one third of its total components (including the most expensive ones). That wouldn't even be feasible for a small company building 50'000-100'000 boards.


Like @slh said. There's no way someone could assist you with such a process over the Internet without extended documentation. The research required, you should know already - and not have to ask.

THIS REQUIRES ADVANCED UNDERSTANDING OF THE INDIVIDUAL BOARD, THE ORIGINAL CHIP, AND THE ONE YOU INTEND TO REPLACE IT WITH. If your have progressed this far, you should know this; and how to replace the WiFi chip.


Slh, many thanks for the exhaustive answer.
It was a bad idea. :slight_smile:

You could cut the PCIe bus wires between the CPU chip and the wifi chips and connect them to a PCIe wifi card instead, but that is still a lot of work.

Better to replace the whole router or utilize it in a wired-only role.

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In short trash it LOL...

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