I was bored a few days ago so I decided to take my NFB-12 apart.
It's impressive how easy it is to disassemble the unit. Only a few screws and everything slides right off. Well, almost. The ribbon cables inside are glued to the side of the case using what I guess is black hot melt glue. When I opened the case to change settings the first time, I mistook this glue for black epoxy. I'm glad it's not epoxy after all, because if it was, it would be impossible to take the board out of the case without a soldering iron.
I noticed a square of double-sided tape/foam on the board between the power inlet and the transformer. Being a bit too curious, I took it off. It's actually covering some jumpers used to change the unit voltage between 120v and 240v. My unit is set for 120v. I checked the pictures on Audio-gd's website and noticed that the unit pictured is 240v. So for anyone who would need to change the voltage settings of their NFB-12, here's a little montage I did :
The settings are actually printed on the board, but it's not very clear. For 120v, you link the two pads aligned with the "110v" prints, same thing for both prints.. For 240v, you link the two pads aligned with the "220v" prints, and you let the other two pads open.
I then proceeded to cleaning the whole board with isopropyl alcohol and a fine brush. It's shocking how dirty the inside of the unit is. I actually had to clean it 3 times over before reaching an acceptable level of cleanness. The board seems to be covered with a sticky dust. I'm thinking it's dust that stuck to the soldering paste during the building process.
Here are some pictures of the underside of the board. Sorry for the crappy quality and the flash, I did the best I could with my phone's camera.
Still being bored at this point, and having learned that the glue was not epoxy after all, I decided to replace the LED. I used an old, low intensity orange LED. No soldering was necessary, only a hot glue gun. I also decided to do something about the heat coming from the unit. Not that the NFB-12 is overly hot, it's just that I can't sleep at night knowing that there's a simple fix to lower the temperature inside the case : let it breathe. Studying the build, I noticed that the PCB sits high inside the case while leaving noticeable gaps around the walls. Using simple fluid mechanics, I concluded that I needed to drill holes at the lowest point and the highest points inside the case. The first step was to drill a series of 1/4" holes on a strait line along the middle of the unit, right trough the bottom of the case. Since heat is generated (or wasted, depending on your point of view) just about everywhere inside the unit, drilling holes bellow the circuit board and in the middle of it allow the heat from under the board to slip in the gap around it and go up, being replaced by cool air. This way, even the heat from the surface mounted components is dissipated. A lot of heat is also wasted out of the transformer and the PSU, dissipated by the multiple heat sinks on top of the board. All this heat goes up and out trough the gaps around the top cover. I placed washers between the cover and the case under every screw. This way there's a 1mm gap all around the case that allow warm air to flow out. PLEASE don't use metal washers if you plan on doing that!! I don't want to be responsible for a washer dropping inside your NFB-12 and shorting the hell out of everything it gets in contacts with. I used rubber washers, anything not conductive would do.
The difference in temperature after this simple modification is impressive. Now the case is barely warm. I don't think it can even melt chocolate anymore. And it just looks more serious without the silly I'm-gonna-blind-you blue LED.