Perhaps you want (or need) to debrick your WNR3500L, or merely access it via serial console utilizing a USB-TTL cable.  For those who are unfamiliar with the process, it's really quite easy - you don't need to be a Linux expert or hacker to do it.  (We have guides for Mac, Windows, and Ubuntu 10.04 if you would like to take a peek.)

However, certain runs of the WNR3500L don't include the pinout connection you need to attach a USB-TTL cable, as shown in the photo below.  Don't fret, as attaching pinouts is also pretty simple, assuming you have (or are willing to learn) some basic soldering skills.  I was fortunate to have my father, an electronic engineer with polished soldering abilities, to help me through this installation - many thanks to him.

What You Need

• Solder
• Soldering Iron Setup
• Razor blade/cutter of some type for trimming the pinout
• Solder wick or solder sucker
• Torx T6 screwdriver
• Digi-Key 36 pin header or equivalent (Digi-Key part no. S1012E-36-ND)
• WNR3500L router

Step 1: Remove the Case

Removing the case is simple.  Use the Torx screwdriver to remove the screws from the bottom.

Then, pry the side of the case slightly to release the tabs, and slide out the plastic covers. When you remove the panel(s), be very careful as you can potentially damage parts, e.g., tearing off capacitors. (Thanks Mainer82 for the tip)

Step 2: Trim the Pinout

You'll want to use a razor blade or whatever implement you choose to trim the pinout you purchased to 6 pins.

Step 3: Solder Sucking Time

If your router is anything like mine was, some of the holes on the PCB are filled with solder.  You'll need to remove the solder from these holes in order to insert your pinout.

The pinout for the serial cable is located at JP1 as shown in the photo.  

Use your soldering iron to heat up the solder, and then wick it out, or use the solder sucker.  This is done from the rear side.  Some of the holes required quite a bit of heat to remove, so patience is a virtue here.

Step 4: Insert the Pinout and Solder to PCB

Now, you can place the header in the board and solder it in on the backside.  You will want the longer pins coming out of the main board, of course, so you can easily attach the USB-TTL cable.

See, that wasn't so bad, even if you are new to this sort of thing.  If you have any questions on this tutorial, or on basic soldering techniques, please post to the forums!