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Antique Radio Technical Forum
Brunswick model 15 1930-31

Posted by nom on 04/04/2009 21:45

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:::Sir Neal:
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:::What you have yourself there is a Tee-Ruhh-Effff receiver, not a Super Hot Rodent, such as you have been dealing with before.. . . .no local oscillator. . .and the "carrier" is the feeble received signals RF presence.
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:::This unit is dependent upon taking the wee RF signal at the front end and progressively amplifying that feeble level thru multiple cascaded Variable tuning condenser / coil combinations.
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:::Your set has a set in each of the RF amps 1st grid circuits stages and then thru the final tuned unit at the detector stage.
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:::Since you already receiving stations, we know that all you will need to do now is a tuning in of all of those 4 tuned “sets” to a common frequency.
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:::I can’t see that units sets of tuning condensers vanes and see if any logarithmic tapering of the vane shaping is involved, so lets just go with eyeballing the vanes rotary position and see that the units ganged rotors are then set at a 90 degree plane to the frame of the tuning condenser. . .ergo mechanical mid range and “center frequency”.
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:::Now go to the front of the dial scale and see what the dial scales current frequency calibration is reading.
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:::Whatever that is, will be the frequency to work with on setting your tone modulated signal generator to.
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:::You will be keeping your sig gens RF output level at such a low level, to the degree such that you can just barely ascertain its received audio presence.
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:::You will then be progressively re- attenuating as each stages gain improves.
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:::Initially start at the pre determined frequency and adjust the last. . .4th L-C clusters tuning condenser trimmer for max audio , with your Sig Gens RF input lightly coupled in from from the earlier stages plate circitry.
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:::Then move the RF input one stage back towards the front of the receiver and trim in the 3rd L-C cluster in the same manner previously.
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:::Then move the RF input one stage back towards the front of the receiver and trim in the 2nd L-C cluster in the same manner previously.
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:::Then move the RF input one stage back towards the front of the receiver and trim in the 1st L-C cluster in the same manner previously.
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:::As you get closer to the very front end you will find that the RF input coupling on the frontal stage can be as low as the “gimmick” capacitance such as is presented by the clipping of a signal generator clip onto the INSULATED wire on the previous stages plate wire circuitry .
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:::After sig injection disconnect and tying in a decent antenna for evaluating on air. . . . those stations should now be rolling in.
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:::With you then havingthe 4 different sections of the tuning condenser then all tracking in unison to that tuned in station and amplifying the selected frequency with the combined level enhancing “flywheel effect” of a tuned resonant circuit and the cascaded tubes amplification.
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:::73's de Edd

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:::Wow, EDD...thanks a bunch for giving me guidance. Now I hope that I have the brain power to interpret what you've written. I appreciate all the time you took to give me a proceedure and enlighten me on just exactly what I've got here. I will start the proceedure soon and if I get stuck I'll post questions...Neal
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:It didn't take me long to get stuck. The center frequency is 800kc.
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:I have an intemittent open/short in the audio signal that I have to find before I can go on. By tapping ever so lightly on the chassis, it will loose/gain audio. Could it be a component? Or is it what I just mentioned, An open or a short. My come and go is more prevelant around the tuner.

Lewis, did you find anything in your dusty old manual?
Ed: Were my questions to basic that you've given up on me?...Neal

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Brunswick model 15 1930-31 
nom 03/31/2009 02:04 
Edd 03/31/2009 12:04 
nom 03/31/2009 16:31 
Lewis L 04/01/2009 11:11 
nom 04/02/2009 00:40 
nom 04/02/2009 05:18 
Edd 04/02/2009 16:44 
nom 04/03/2009 02:41 
nom 04/03/2009 09:55 
nom 04/04/2009 21:45 
Edd 04/10/2009 17:23 
nom 04/11/2009 22:24 
nom 04/16/2009 08:15 
nom 04/18/2009 22:40 
nom 04/19/2009 11:29 
nom 04/21/2009 03:52 
Lewis L 04/21/2009 13:42 
nom 04/22/2009 01:32 

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