1 watt seems a little low for 9 volts. IIRC output power should be around 2.5 watts. Have you checked-out your -5B with an accurate power meter? I have never tried my -5B with a 9 volt battery. I use an AGM at 11.6 volts. I put a couple of silicon diodes in series with the B+ side to drop the voltage from about 13 volts closer to 12 volts or slightly lower.