Repairing FM and AM/FM receivers
To a large extent the same techniques as used for AM-only receivers will apply on both AM or FM to the main chassis of the receiver, bearing in mind that on FM the IF is increased to 10.7 Mc/s and the detector works in a different way. The AF amplifier and output stages are similar to those of AM sets only in respect of extending the treble response. More expensive sets were fitted with special high frequency ‘tweeter’ loudspeakers alongside the ordinary unit. Experience has shown that the chief causes of trouble other than those to which any receiver is heir have been breakdowns on the AM/FM switching due to the presence of HT on the wafers and a greater susceptibility to self-oscillation in the IF amplifier ...
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