I bought this used on eBay. I have bought a manual and logic clips for it. I have tried to use it, but the Trace mode never recognizes the 'search word' I have set. I am wondering if I am doing something wrong or if it is actually defective. I have set the probe threshold levels to variable and have the trigger voltage at 3.9 volts on a 5 volt board. I never get a trigger, even though the logic probe shows my test points to be pulsing. I get a warning that I have no trigger. Can someone give me some pointers on this piece of equipment, please?