Yeah I have both the service and operating manuals , the trouble is partly due to the fact I can't follow a schematic very well . I did however set the switch to internal and set the modulation level to 50% , then I switched to 400 hz out and checked my a.c. voltage at the binding posts and I got 1.1 volts . The manual claims 1 volt rms at 50% , so I guess I've got a signal ??? Another forum someone spoke of needing a transformer on a speaker , but I don't understand that part because in the manual they instruct using the 400 hz out tone to troubleshoot a non working radio and the first thing they do is hook the binding posts to the voice coil of the non working radio's speaker . Isn't that just connecting to the + - terminals of the speaker ??? So I don't understand that part . Also does anyone know if the modulation meter works when the switch is on 400 hz out ?? It works for carrier in all positions and works in modulation in all positions except the 400 hz out , so now I'm trying to figure out how to hear the tone thru a speaker and whether or not the modulation meter works in the 400 hz out position . Thanks