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## Re: [Amps] Question about grid current in 4CX or 3CX

 To: dj7ww@t-online.de, amps@contesting.com, donroden@hiwaay.net Re: [Amps] Question about grid current in 4CX or 3CX "sm0aom@telia.com" sm0aom@telia.com Mon, 18 Mar 2019 15:53:08 +0100 (CET)
 ```Usually the Class C grid current decreases somewhat when the plate and screen voltages are applied, due to more electrons are drawn away from the grid. The actual grid dissipation can be estimated as a first approximation by applying Chaffee analysis to the constant-current curves in the data sheets, such as done in the Eimac AB-5. For the 4CX10000D at full ratings in class C, using data sheet values, the grid dissipation becomes the difference between the power consumed by the bias source which is the product of the DC grid current and the DC bias voltage; 350*0,25 = 87,5 W and the driving power 590*0,25 = 147 W = 147-87,5 = 59 W which is less than 75 W which is the allowed grid dissipation. If the plate and screen voltages are removed, the dissipation would increase somewhat, so full drive may not be advisable for longer periods. 73/ Karl-Arne SM0AOM ----Ursprungligt meddelande---- Från : dj7ww@t-online.de Datum : 2019-03-18 - 09:19 (CEST) Till : donroden@hiwaay.net, amps@contesting.com Ämne : Re: [Amps] Question about grid current in 4CX or 3CX Hi Don, The grid dissipation of the 4CX10000D is 75W. It takes 150W of drive for 250mA of grid current with that tube in class-c with anode and screen voltage supplied. Are you thinking of a different tube? 73 Peter -----Original Message----- From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of donroden@hiwaay.net Sent: Freitag, 15. März 2019 16:38 To: amps@contesting.com Subject: [Amps] Question about grid current in 4CX or 3CX Question : For the larger tubes with handles ( commercial service ) Does grid current increase or decrease as plate voltage and screen voltage is removed. ? If it takes 250 watts to produce 100ma of grid current in a 4CX10,000. is the grid just a big dummy load and is it doing the tube harm to dump 250 watts into it when both plate and screen voltages are removed ? Don W4DNR _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ```
 Current Thread [Amps] Question about grid current in 4CX or 3CX, donroden Re: [Amps] Question about grid current in 4CX or 3CX, David G4FTC Re: [Amps] Question about grid current in 4CX or 3CX, Peter Voelpel Re: [Amps] Question about grid current in 4CX or 3CX, sm0aom@telia.com <= Re: [Amps] Question about grid current in 4CX or 3CX, donroden [Amps] Question about grid current in 4CX or 3CX, Jim Thomson