If there are two leads on each device, it sounds like resistors (barrel shapped) and capacitors (teardrop) which are probably for filtering electrical noise. Transistors will have 3 leads but are not usually barrel shaped or teardrop. If they are added on the outside of the panel it is likely an afterthought kludged on because the panel failed some FCC emissions or succeptibility EMI testing and they didn't want to make a design spin.