Hi. I just bought a GTA 350 off of someone from EBAY. I was told it was only less than 2 years old. Now that I have the machine GARRETT tells me it is much older, more like from 1994 or 1995. I guess I can't complain since I only paid $115 for the unit, case, and headphones. I also have two Ace 150's for my boys. I might put the 350 back on Ebay to sell and get me a 250....I hear the 250 is the best detector for the money in any brand. Anyway, I was experiencing this cracking sound as well. I suggest that you turn on the unit and then hold the power button down for at least ten seconds or until you hear a beep tone. This will reset your machine to the factory descrimination settings. As for the cracking sounds, I still get them on occassion and have learned that the signals are just junk. Something good will give you a good clear tone. As for pull tabs, I still think we all still dig those pesky things up. Also, if you need a manual, just do a google search and you can pretty easily find one and print it out. Good Luck!!