hi all ive just built this :http://www.electronics-lab.com/diy-generic-curve-tracer/ ,it sort of works,however when i look at a diode junction it only gives a display with the diode hooked up in one direction,in the other direction the display shows a horizontal line ie open circuit,on my old huntron it used to invert the display,also when i try to test a cap it shows a verticle line ie short,it seems to measure resistance ok,ie the trace rotates with a variable pot across the probes,any ideas?.