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1. [Amps] complicated Bias circuit (score: 1): Author: Paul Decker <kg7hf@comcast.net>; Date: Mon, 5 May 2014 01:18:47 +0000 (UTC); Hi builders. Hopefully you all can view this schematic. I'm trying to understand what T2 and associated circuitry do. D17 and D18 seem like a simple bias circuit as SW3 selects between "class C" and; /archives//html/Amps/2014-05/msg00003.html (7,573 bytes)
2. Re: [Amps] complicated Bias circuit (score: 1): Author: Paul Decker <kg7hf@comcast.net>; Date: Mon, 5 May 2014 01:49:09 +0000 (UTC); FYI, if it helps any, this goes to a 3cx800A7 amplifier of some sort. Hi builders. Hopefully you all can view this schematic. I'm trying to understand what T2 and associated circuitry do. D17 and D18; /archives//html/Amps/2014-05/msg00004.html (7,426 bytes)
3. Re: [Amps] complicated Bias circuit (score: 1): Author: MU 4CX250B <4cx250b@miamioh.edu>; Date: Sun, 4 May 2014 20:22:36 -0600; Paul, In standby, the 24V from T2 just biases the tube(s) to cutoff. R20 by itself would almost do this, but without the 24V there would still be some small cathode current in standby which could gen; /archives//html/Amps/2014-05/msg00005.html (9,556 bytes)
4. Re: [Amps] complicated Bias circuit (score: 1): Author: "Joe Subich, W4TV" <lists@subich.com>; Date: Sun, 04 May 2014 22:27:19 -0400; The bias supply is *negative* DC ... where do you expect to get it other than a separate low voltage supply? This bias supply is hardly complicated ... it is a scaled copy of the circuit used in man; /archives//html/Amps/2014-05/msg00006.html (8,598 bytes)
5. Re: [Amps] complicated Bias circuit (score: 1): Author: Paul Decker <kg7hf@comcast.net>; Date: Mon, 5 May 2014 02:30:09 +0000 (UTC); Hi Jim, Thanks, that is what I needed to get me going. I couldn't see the exact need for the T2 circuitry since D17 and D18 were still the traditional high power 50W zeners. I would have thought sinc; /archives//html/Amps/2014-05/msg00007.html (10,256 bytes)
6. Re: [Amps] complicated Bias circuit (score: 1): Author: peter chadwick <g8on@fsmail.net>; Date: Mon, 05 May 2014 08:37:26 +0200; You cannot cut off a tube with cathode self bias. So to really cut it off in receive needs an extra supply. vy 73 Peter G3RZP _______________________________________________ Amps mailing list Amps@co; /archives//html/Amps/2014-05/msg00008.html (7,112 bytes)
7. Re: [Amps] complicated Bias circuit (score: 1): Author: "Paul Christensen" <w9ac@arrl.net>; Date: Mon, 5 May 2014 08:01:32 -0400; "I think there is no QSK because this amplifier is designed to be either keyed, or off it is from a TX only system. I wanted to modify it for TX/RX by adding a relay in the bypass line of R20 to put; /archives//html/Amps/2014-05/msg00009.html (12,234 bytes)
8. Re: [Amps] complicated Bias circuit (score: 1): Author: Paul Decker <kg7hf@comcast.net>; Date: Mon, 5 May 2014 23:41:21 +0000 (UTC); Thanks Joe, What I meant by complicated is more that I haven't seen a bias circuit like that in any amateur publication. I dug through a few handbooks dating back to 76 and the only circuit close was; /archives//html/Amps/2014-05/msg00011.html (8,685 bytes)
9. Re: [Amps] complicated Bias circuit (score: 1): Author: Paul Decker <kg7hf@comcast.net>; Date: Mon, 5 May 2014 23:59:57 +0000 (UTC); Hi Paul, Agreed! But it's in my shack now, while I don't need qsk, I do need TX/RX capability. you should see the inside of the power supply and the RF decks, absolutely gorgeous and stunning constru; /archives//html/Amps/2014-05/msg00013.html (9,237 bytes)
10. Re: [Amps] complicated Bias circuit (score: 1): Author: Steve Gorecki VE3RX <ve3cwj@gmail.com>; Date: Mon, 5 May 2014 12:25:02 -0400; Paul, it looks like +ve bias for the cathode of the tube, meaning it is likely a grounded grid design. R20 is for RX as well, I suspect, providing further bias to cut off the tube idle current (reduc; /archives//html/Amps/2014-05/msg00018.html (7,937 bytes)

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