This is a TRF set and needs a good antenna to operate properly. Did you connect to an outdoor antenna? Check that the audio stages are OK: touch the bare end of a five foot long piece of insulated wire to the grid terminal of the 27; a loud hum means the audio section is OK. Also: good idea to check the tube socket voltages in the chart on the schematic on Nostalgia Air:
http://www.nostalgiaair.org/PagesByM...2/M0029582.pdf
Your voltages will read higher with a DVM as the meters used in the heyday of the model 20 loaded the circuits down more. For example, the diagram says to expect about 215 volts on the plates of the 71-A's, the highest B+ voltage in the radio. Whatever you actually read there will be higher, and you could expect proportionally higher B+ voltages throughout. If you find a voltage that seems "off," look for trouble in that stage, resistor value gone way high ,etc. Have fun poking around in there!
Reece