loewe f875 sensotronic chassis f800 11


Posted on Feb 7, 2014

The LOEWE F875 SENSOTRONIC CHASSIS 543/490 is realized with the F800 LOEWE Chassis serie and in the Line / Horizontal deflection output like a COLOR TELEVISION CHASSIS with EHT output with Tripler and Horizontal output with thyristor tech. LOEWE-OPTA Start-delay overload protection arrangement for a thyristor sweep circuit:An input switching thyri


loewe f875 sensotronic chassis f800 11
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stor of a deflection circuit is selectively excited at a sweep rate by a transistorized driver stage. A separate protective thyristor is disposed in a DC power source that supplies operating bias to the driver stage and to the switching thyristor via a supply capacitor. Initially, the supply capacitor is partially charged through a high-ohmic shunt resistor that budges the protective thyristor, whose control electrode is coupled to the output of the switching thyristor. A portion of the resulting voltage across the partially charged supply capacitor is applied via a voltage divider and a Zener diode to the base of a threshold-operated transistor that normally blocks the driver stage. When the supply capacitor has charged to a predetermined minimum value necessary to assume turn-on of the protective thyristor, the threshold-operated transistor is triggered to permit the driver stage to operate the switching thyristor at the sweep rate. The resulting turn-on of the protective thyristor permits the rapid completion of charge of the supply capacitor to its normal operating voltage, and thereafter provides full overload protection for the deflection circuit. 1. In a communications receiver wherein (a) a first input switching thyristor of a deflection circuit in the receiver is pulsed at a sweep rate by a driver stage when the latter is excited, (b) a supply capacitor is chargeable through a second protective thyristor by-passed...




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