164
Item nr.
A Van der Heem design.
Production | The Netherlands, 1950.
Price was 198 guilders. |
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Bands | LW (950-2000m), MW (175-580m), SW (15-55m). |
Tubes | ECH42 EF41 EBC41 EL41 AZ41. |
Cabinet | Wood. Size 38x25x21 cm. Weight 6.8 kg. |
Power | AC 110-250V, 40W. |
Documents | Schema of Erres KY504. |
Let me mention that around 1950 it was popular to obtain the negative grid bias from a resistor in the B- supply. More commonly, this grid is at (DC) ground level and the catode lead of the tube contains a resistor bringing it to a positive level. Such a cathode resistor would of course only pass the catode current for one tube, but the resistor (and its decoupling capacitor) must be repeated for various tubes. This radio, and also the famous Philips BX591A types for example, used the different way: the resistor in the B- builds up a real negative potential against ground, and this is fed to the grid. The resistor is decoupled by a 100uF electrolytic capacitor and taps supply the (lower) bias for the RF tubes. Because the B- resistor (of value 100 to 200 Ohms typically) runs the current of all the tubes, its decoupling is critical. The capacitor often dries out and looses its capacitance, leading to oscillations.
Obtained | 10/2000 from Winkeltje van Sinkeltje. |
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Condition | 8. |
Disposed | Sold 1/1900. |