WRT (1200AC, 1900AC/V2 & WRT1900ACS) hardware tweaks

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Tweakster
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Joined: 19 Jan 2018
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PostPosted: Fri Jan 19, 2018 16:55    Post subject: WRT (1200AC, 1900AC/V2 & WRT1900ACS) hardware tweaks Reply with quote
Hiya everybody!

I have found the area to mod on the main boards to make each model into region specific WiFi compatible devices. So your router can use more bands if needed.

Plus if anyone can post an image and region (US, AU, EU, UK), device model and version. I can make a data base of what toggles need to be done.

To help, all you need to do is to power off and disconnect your router, and unscrew the 4 bottom screws in the feet.

Pull the blue front cover off.

Carefully with a small pocket knife carefully pry directly under the lip at the top from the back side. If you have the unit on its back you will see the seam. The bulky leg sections are part of the cover and slide over the bottom frame. So the unit looks one piece but once you get a corner started, you will pop off the top fairly painless.

Remove the antenna cables from the main board.

Remove the two small screws holding the main board to the plastic bottom, and left out and away.

Flip the main board over and remove the heat sink, by unscrewing the 4 screws that hold it in place. You may have to pull on the heat sink, while lightly twisting back and forth. The heat sink has alignment rings that keep secure in the circuit board mounting holes, and limit screw mounting pressure from cracking the board.

Once you have the heat sink off. The area needed is seen to the right above the 4 lan connections on the printed circuit. It has a white boarder with Boot Device Mode Options written along the top.

Here is my WRT1900AC/V2 US version.



Last edited by Tweakster on Sat Jan 20, 2018 0:47; edited 3 times in total
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Tweakster
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PostPosted: Fri Jan 19, 2018 17:49    Post subject: Boot Device Mode Options US version WRT1900AC/V2 Reply with quote
To read the switch options, there are two blocks of 3 bits used for model and region. LSB (least significant bit) block of 3, starts left, with two rows (top is off, bottom is on). Only one chip resistor is used per column.

Example: On Off Off would be bottom location would be populated and top location is left open. The next two would have a chip populated on the top two remaining columns.

Mine reads... Off On Off for the LSB block, and On Off Off for the MSN block.


Last edited by Tweakster on Fri Jan 19, 2018 20:09; edited 1 time in total
Tweakster
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Joined: 19 Jan 2018
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PostPosted: Fri Jan 19, 2018 19:41    Post subject: WRT1200AC... same board as WRT1900AC/2 & ACS Reply with quote
Off Off On On Off Off

Seems like model ID is the LSB block of 3 bits. Since it matches my MSB block of 3, I assume it is also a US model.
Tweakster
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PostPosted: Fri Jan 19, 2018 20:08    Post subject: WRT1900ACS/V1 Reply with quote
Off On Off On Off Off

Same as my WRT1900AC/V2 and again I assume it is a US model, because MSB block matches mine.
ValCher
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Joined: 26 Jan 2018
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PostPosted: Fri Jan 26, 2018 14:13    Post subject: Reply with quote
@Tweakster
Oh, that's a good observation.
Tell me, can this change the region for the Wi-Fi wireless module?
d0ug
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Joined: 31 Jul 2015
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PostPosted: Fri Jan 26, 2018 20:58    Post subject: Reply with quote
These aren't two blocks LSB/MSB.

LSB = Least Significant Bit
MSB = Most Significant Bit.

https://en.wikipedia.org/wiki/Most_significant_bit

What we are looking at there is basically a 6 bit binary variable, set in hardware using resistors, actually probably 0 ohm jumper links.

The resistor in one position probably ties the bit to ground and in the other position to +5, +3.3 or some other positive voltage rail, basically making a pattern of 1's and 0's

With 6 bits, that means there are 63 possible different configurations

Would be very interesting to find out what different combs do!

Attached is an image of the options set on my USA WRT1200AC v2

It would appear the upper position would be 0 since it appears tied to the ground plane, so it looks like

010100

Since mine is the same as the WRT1900 posted above, it does not look like this is model specific where it might control CPU clock speed. We will have to wait for some from other regions to see if it changes outside the US.

Considering the name on the silkscreen it could also be something completely benign like what to boot off of, such as a choice to boot from EMMC, USB, or SATA
d0ug
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Joined: 31 Jul 2015
Posts: 760

PostPosted: Fri Jan 26, 2018 21:57    Post subject: Reply with quote
Looking at pictures of other WRT boards online, it doesn't even look like all the models have it. This is of a WRT1900 v1, since it has the removable radio modules. I am not seeing that silkscreen anywhere on the board

https://www.nikktech.com/main/images/pics/reviews/linksys/wrt_1900_ac/linksys_wrt_1900_ac_17.JPG

Here's another review showing board shots and I don't see a silkscreen on either the mainboard or radio board, unless it is on the bottom side of the board

https://www.eteknix.com/linksys-wrt1900ac-dual-band-wireless-router-review/2/
ValCher
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Joined: 26 Jan 2018
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PostPosted: Fri Jan 26, 2018 23:47    Post subject: Reply with quote
Measured the voltage on the wrt3200acm

d0ug
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PostPosted: Sat Jan 27, 2018 0:16    Post subject: Reply with quote
ValCher wrote:
Measured the voltage on the wrt3200acm



Interesting, did kind of suspect that they might be going to different + voltage rails since the left 3 are tied together on one trace and the right 3 are on their own traces.

Could very well mean the left 3 are doing something with the SOC, and the right 3 are doing a config for something else, wifi, or switch chip maybe. The fact that each of the right 3 have their own + traces could indicate that each one is doing something with a different component and that + rail is referenced to the + rail at the chips VCC, or all 3 are just bonded together on the bottom, or internal layer. Though not sure why they wouldn't have just done it like they did the left 3
ValCher
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Joined: 26 Jan 2018
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PostPosted: Sat Jan 27, 2018 10:42    Post subject: Reply with quote
I think this is intended to select the default bootstrap and configure the internal units of the SOC Marvell.
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