Even without any signal, you should still hear RF noise on the weather frequencies with the squelch open. I would still try resetting plugs and reloading the firmware before going to the expense of shipping the scanner back for repair.. If the firmware is corrupted, that could prevent the scanner from receiving signals. I have seen a couple of Pro-197's, the older brother of your scanner, with a blown audio output IC, but that did not prevent the scanner from receiving. Incidentally, the Pro-652 is not a GRE scanner. It is a Radio Shack scanner manufactured by Whistler for Radio Shack using the original GRE design. The Whistler WS1065 is the same scanner. The Pro-197 was the same Radio Shack scanner made by GRE for Radio Shack. Make sure you use the Pro-651/652 firmware updater. Although the scanners are the same, they use different firmware. Loading the wrong firmware can brick the scanner.