Originally Posted by howardcano

First do a visual inspection of all components. Some of them have polarities that must be observed. We've already mentioned the capacitor. Check the transistors also; emitter must go to the square pad. (You can download spec sheets for the components from Mouser or Digikey.) Reversed transistors could easily explain the voltages you are seeing (since the current gain of a bipolar transistor isn't too good when the emitter and collector are swapped!).

Next would be an inspection of all solder joints. It's pretty easy to bridge connections on the loop amp board.

Anything past that will require an oscilloscope.