• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

radio receiver

Those metal tubes can get pretty hot - shouldn't be any doubt once it's been on a few minutes...
ect. Some hum is a good sign.

If there's no sound at all from the speaker, the speaker field coil or output transformer is susp
Schematic is here: http://www.nostalgiaair.org/PagesByModel/498/M0021498.pdf

No voltages listed - but if you can measure the voltages at each tube socket pin, it shouldn't be hard to diaqgnose. BUT... if you haven't worked with high voltage before, you should find an experienced person to help and point out the hazards. This set has a power transformer, so shock hazards are less likely but MORE DEADLY.