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Old 26th May 2019, 12:56 am   #1
martin.m
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Join Date: Mar 2018
Location: Bishop Auckland, County Durham, UK.
Posts: 287
Default Hacker Autocrat RP33

This AM only radio dates from the late 1960s and uses AF117s in the RF and IF stages. I bought it as non working and was surprised to find that these transistors had been replaced with shiny new-looking AF124s. There was no sound but the audio amp was working as there was a faint hiss when the volume was turned up. The Autocrat runs from an 18 volt supply provided by a pair of PP9 batteries. However the supply for the RF/IF circuits is dropped down to around 9 volts by a 1.5k resistor and decoupled with a 350uF electrolytic capacitor. Measuring this supply rail produced a reading of only 4 volts. I changed the capacitor, which is next to the volume control, for a new 470uF 25v. This restored the 9 volt supply and the radio burst into life. The Hacker Democrat uses a very similar IF panel and the usual cause of low supply voltage is inter electrode shorts in the AF117 transistors.
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