I just got a used Akai Deep Impact pedal. Problem is this: when I engage the on/off button, sometimes the selected effect engages. At other times, nothing beside a crackling sound is happening. No effect sound, no LED blinking. It seems that there is a bad connection. I have opened the unit but can't find any blatant bad soldering. Has anyone else experienced the same issue? Has this pedal really a true bypass? There are only 2 wires connected to the on/off switch.