Restoration methods

A brief guide to troubleshooting the old radios

Absence of Signals

  • Burnt out rectifier valve
  • Broken down filter capacitors
  • Open-circuit field winding or filter choke
  • Short in H.T. by-pass capacitors
  • Open circuit cathode resistors
  • H.T. supply line open circuit
  • Open circuit R.F. or I.F Coil
  • Shield can shorting to grid cap
  • Disconnected wiring
  • Faulty valve socket or speaker connection
  • Low B+ Voltage

Poor Volume

  • Weak valves
  • Low H.T. or filament voltage
  • Poor alignment
  • Open circuit R.F. or I.F. coils
  • Faulty volume control
  • Incorrect valve types
  • Leaky high voltage caps


  • Open circuit bias or grid resistors
  • Audio feedback
  • Low emission valves
  • Incorrect voltages
  • Leaky coupling capacitors
  • Gassy output valve

Crackles & Whistles

  • Faulty resistors
  • Faulty capacitors
  • Loose contacts at sockets
  • Dry joints
  • Faulty output transformer
  • Faulty power transformer
  • Ineffective valve shield (Whistles in particular)
  • Faulty valve
  • Poor wiring layout
  • Poor alignment


  • Poor filtering
  • Short between cathode & heater
  • Poor shielding on audio leads
  • Bad rectifier
  • Faulty electrolytic capacitor

Severe Hum

  • Shorting electrolytic capacitor
  • Internal fault in rectifier
  • Shorted field coil or H.T. choke

No Shortwave reception

  • Dirty wave change switch
  • Resistors high in R.F. stages
  • Weak frequency changer valve
  • Low H.T. voltage

Low High tension

  • Weak rectifier valve
  • Faulty power transformer
  • Incorrect speaker
  • Faulty valve

Rectifier glowing red

  • Direct short on H.T. Line. (e.g. Electro filters)

Output valve red

  • Open circuit anode on output valve
  • Open circuit output transformer
  • Speaker unplugged

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