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Philips |
Model 446A |
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Schematic: |
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This
is an AM receiver sold in Switzerland in the year of 1942. It operates in
two wavebands, namely, 13.7 to 51m and AZ1 full-wave rectifier (data sheet PDF, 66KB); EBL21 used in the detection circuit, the AGC circuit and in the output stage. Diode 1 - AGC, diode 2 - detection and Pentode - output stage (data sheet PDF, 41KB); ECH21 used in the frequency converter stage. Heptode - mixer and triode - local oscillator (data sheet PDF, 75KB); EF22 pentode, used in the IF amplifier stage (data sheet PDF, 48KB); EF22 pentode, used in the audio preamplifier stage (data sheet PDF, 48KB); EM4 tuning indicator (data sheet PDF, 21KB). If you are curious about the technical details, you will find next the schematic diagrams of the set. Please note that these have been "reversed engineered" by my self and they might be inaccurate (although I don't think so). To repair the set some of the components had to be replaced. Since the component values were in many cases illegible the values marked in the schematic are the result of a bit of guesswork. The annotated voltages have been measured after the receiver has been repaired (it works fine). Aerial Circuit and Local Oscillator (schematic JPG, 49KB); IF stage, Detection, AGC and Magic Eye circuit (schematic JPG, 40KB); Audio amplifier (schematic JPG, 42KB); Power supply (schematic JPG, 69KB).
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