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

• Radio Station Missing

• Radio is not turned on

• Radio is missing

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

• Your Hearing Aid is Faulty

• Radio is too far from your ear

• Partner has removed long wire antenna

Distortion

• Open circuit bias or grid resistors

• Audio feedback

• Low emission valves

• Incorrect voltages

• Leaky coupling capacitors

• Gassy output valve

• Radio not designed for Led Zeppelin

• (Relocating Tuner to 693 Magic should cure problem)

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

• You are listening to New Years Celebrations

• Radio is on fire

Hum

• Poor filtering

• Short between cathode & heater

• Poor shielding on audio leads

• Bad rectifier

• Faulty electrolytic capacitor

• Singer didn't know the words

Severe Hum

• Shorting electrolytic capacitor

• Internal fault in rectifier

• Shorted field coil or H.T. choke

• Several singers didn't know the words

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

• Partner is satisfied you won't burn house down

Rectifier glowing red

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

• Somebody put a 3 pin plug on the battery cables

Output valve red

• Open circuit anode on output valve

• Open circuit output transformer

• Speaker unplugged

• Incorrectly aimed Spray Pak during restoration

• Set is on fire