About
In a previous article (here) I discussed the overheating problem of the Fonera model 2100, with the power regulator reaching 70°C and the cpu getting around 60°C. In the article I also discussed some possible solutions.The solution
The soution I selected is not listed in the previous article, and is this: to remove the power regulator from the circuit, and to place it on an heatsink outside the fonera case. With this solution I hoped to reduce the temperature of the voltage regulator itself and, since less heat is generated inside the fonera case, to also reduce the temperature of the cpu.The solution was so simple and elegant that it didn't work, of course. The problem was that I broke the voltage regulator while removing it from the printed circuit. However this wasn't a big problem, because it is a fairly common part, an LM1117-3.3 so I simply bought a new one, and I also chose it in the TO220 package, that is easier to mount on an heatsink than the original chip. Once solved this little problem, it worked flawlessly. Here are two pictures of the result.
And now some info about the temperatures: With the cpu in full load (yes > /dev/null running) the voltage regulator is around 45°C, that's 25°C less, while the cpu is around 52°C, which is 6°C less.
As you can see, the voltage regulator, as expected, has a much lower temperature because it is mounted on an heatsink and is outside the fonera case, and that's a success. The cpu temperature did not drop as expected, though; at this point I ask myself which are the differences between the fonera 2200 that is so cool that it doesn't even have an heatsink on the cpu, and the 2100. This mod proves that the difference is not merely the switching voltage regulator; anyway, I have no idea, maybe they overvolted the cpu?
A few notes for those who may want to try this mod.
1) Don't try this if you don't already have an LM1117-3.3, since you'll probably damage the chip while trying to remove it, so you'll need a replacement part.
2) Keep the metal tab of the LM1117 insulated from the heatsink, since it is electrically connected to +3.3V.
Update Mar 09, 2009
Added images to help understanding where to connect wires on the printed circuit of the Fonera
