Ok here is my situaiton...had a beater jazz with a set of coblalt noiseless pickups.. bough a cheap "Artec" preamp off of ebay (used these before with good results- basically a reverse engeneered chinese EMG pre) it has a blend pot with a soder in for the hot wires, from the pickups (1 each) and 1 connection for the ground- (twisted and soldered both wires together, soldered a lead wire from the two and into that in ( which is how I have done it previously) strangley now, I have no signal comming from my bridge pickup. When I turn the blend pot back to solo the bridge pickup nothing- soloed neck no problem have sound. Double checked to see if lead wires and ground were making connections and even resoldered all.. same problem. Tried messing with the jack- only got no signal at all- so pretty sure jack is right- ( and is stero) all other connectections appear to be making contact and well soldered. Pickups had no wires orginally but I added them following diagram. Red (or hot) wire is soldered on both pickups and the attachement closest to the neck black (or ground) is soldered at attachement closest to the bridge...reversing these caused loss of signal and a radio station...so I think have those right...anybody have any idea?