The MFJ-259 antenna analyzer is a handy device for checking antennas and transmission lines. They often appear at ham fleamarkets for reasonable cost.
Sometimes the band switch on the MFJ-259 analyzer becomes intermittent, making the generator section unstable. It would be difficult to find a replacement switch, so the next best solution is to open it up and clean it. Luckily, it isn’t necessary to desolder it from the circuit board – there are 4 plastic tabs visible at the sides of the switch that hold it together. Using a small screwdriver gently pry the tabs away from their resting place and the top section of the switch will come off.
The contacts on the switch can now be cleaned. I suggest DeOxit as a good contact cleaner – not WD40. Make sure you don’t change the position of the switch wafer while you have it apart or else the pointer on the band switch knob might not indicate correctly.