Have a Zenith H-500 tubes do not appear to be lighting and all I have is a very low hum coming from speaker,anyone with some ideas
Thanks,Clay

Clay: here is your schematic: http://www.transoceanic.nostalgiaair.org/h-500.htm

You can begin by pulling each tube, and checking its filament for continuity with an ohmmeter. If all the filaments are OK, then you'll need to troubleshoot in a systematic manner with your voltmeter, comparing the voltages to those shown on the schematic.

The filaments in those small tubes are sometimes hard to see even when they are lighted.
Doug

:Have a Zenith H-500 tubes do not appear to be lighting and all I have is a very low hum coming from speaker,anyone with some ideas
: Thanks,Clay