When I turn on the electrical master switch, quite often I need to cycle the switch numerous times for power to come on. Sometime when I put the switch on I have power, but if I then put the radio master on or the starter on the power will fall off. I can always hear the battery solenoid clank on but no power. Sometimes it work fine, but I never know when I go out to the airplane if today it will work or not. I have replaced a perfectly good Concord battery, a perfectly good Electrical Master switch, I have replaced two new Sky-tek battery solenoids. I have replaced both wires from the Electrical Master switch all the way back to the battery. I have had the shop replace numerous grounds. No one can figure out what the problem is; anyone ever run across thjis before? any suggestions?