grundig: 5040W/3D (5040 W/3 D);

What is the reason that the cathode resistor has no bypass capacitor? I have experimented with my 5040W/3D by adding a 100 Uf 50 volt capacitor and there is a noticable difference in audio gain and bass response, however, I realize that Grundig didn't typically leave anything out. What have I compromised by adding the capacitor, if anything??

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Dear Ross,

The cathode resistor gives a DC drop to properly bias the grid of the output tube. The cathode capacitor, when used, acts as a low-impedance path, something like a short-circuit, for audio frequencies. Removing the capacitor, Grundig added some AC feedback, to improve the fidelity of the output stage. Gain was more or less decreased, but they had power enough from the EL12.
 

Regards, Emilio

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Thank you, Emilio, for the clarification. I added the capacitor over a week ago, and am realizing that although there is an increase in gain, there is also more distortion. I also noticed that the action of the treble control is  odd and the loudness contour feature of the volume control is abnormal as well. I'm going to remove this capacitor now that I have realized the  effects it caused. Thanks again, Ross

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Ross,

Do you have a user or owner's manual for this radio?  I just purchased a 5040 (German model) that I plan to refurbish, but it would be nice to know how it was suppose to work.  I have schematics and technical drawings, but not an owner's manual.  Any clue where to find or purchase one would be helpful.  Regards,

Jim

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Hi, I may have one, I'll check the 5040 file and see. I'll try to respond tomorrow. Thanks!! Ross

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