FAULTS 



Electrolytic capacitors 



Loss of capacitance and 

 increase of leakage 

 current with old age 



Leakage current becomes so 

 great that the temperature 

 rise produced leads to evolu- 

 tion of gas and eventual 

 explosion. (This should 

 never happen if the circuit 

 is properly fused) 



Potentiometers 



With old age, slider 

 begins to make poor 

 contact 



Rare 



EHT transformers 



HT transformers 



Gradual failure of 

 insulation 



Rare 



Winding open circuit — usually 

 a burn-out as a result of 

 overload by a fault condition 

 elsewhere (e.g. electrolytic 

 capacitors) 



Valves 



Gradual loss of cathode 

 emission 



Heater open-circuit 



Regulator tubes 



Gradual drift of running 

 voltage 



Rare 



Wiring 



Corroded soldered joints 

 due to use of unsatis- 

 factory flux. 



'Dry' joints, due to 

 inefficient cleaning of 

 surfaces before 

 soldering 



Short circuits caused by the 

 bridging of soldering tags by 

 metal fragments (e.g. drilling 

 chips) inadvertently left 

 behind after assembly of 

 work 



666 



