This set has a full-wave rectifier. Bad filter caps will produce a 120-Hz hum, not 60 Hz.

It's useful to be able to quickly tell the difference between 60 Hz and 120 Hz (without a 'scope). I bill myself as a tenor, and can just barely match a 60-Hz tone. Humming at 120 Hz is very comfortable.

Here is the schematic: http://www.nostalgiaair.org/PagesByModel/832/M0028832.pdf
Doug

Sir Neal: Dragging tuning condenser plate. . . tsk. . .tsk. . .BUT there were a BUNCH of potential candidates ! ! ! Your main filters of interest on that set are shown in incremental order. . .with the #1 unit being the most critical, and progressively on down the numerical line. Probably no fault with the [ORANGE] resonating capacitor unless it has opened up. Can we also assume that none of the speaker / output transformer wiring has been messed with. . .I mention this because the design of the AF output circuitry design of this set varies from the norm. Herein is the difference: One usually sees the AF output transformer receiving its swinging AF feed from the plate of the output transformer and coupling on to the speaker via its secondary low Z winding. (Your set merely has an extra output tube in parallel) NOW here is the real difference in your set. . .it is double dipping. . .look at the plate circuitry referencing of the plate line highlighted in [BLUE] and see the line coming down and ending up at the speaker field coil winding. Normally one sees the field coil winding used solely for the magnetizing of the electromagnet core in the speaker, and for filtering action in the power supply, not so in this case. That winding is receiving the AF signal from the plate , just as an output transformer normally would, and its magnet field strength is varying in unison with the audio strength and content. Its usual / additional filter choke function is not necessary here, since that is fully taken care of by the hefty 15 henry choke down there to the left along with its accompanying pi filter network. Now, re-examine the plate feed and you see at the broken [BLUE] feed line, that it is additionally capacitively coupling [5] its AC audio component to the output transformer, with the total audio AC ground path then being completed via capacitor [6] wider broken [BLUE] line. NOW with that varying magnet field strength of the speaker working against the normal magnetic field produced by the voice coil winding, one can get more than the normal excursion of the speaker cone. Unless you might have incurred a phase reversal between the two fields, that is why I asked about that associative wiring, merely rapid reversing of ONE pair of the leads will confirm, when comparing the two produced volume levels. 73's de Edd

CLARIFIED BRUNSWICK #15. . . . . . MARK-UP SCHEMATIC :

::::: ::::: ::::: ::::: ::::: ::::: :::::My Caps are in. Not in the radio but they have arrived. I've pulled the entire capacitor block out of the set. It's a solid mass of, I don't know what you would call it, but all the capacitor leads go in one side of this big brick of substance. It's about 3 X 5 X 4 inches. Amazingly all of the capacitors are still pretty close to the right capacitance. So I'm hoping they were leaking. I am counting on this to take care of my background hum...I'm studying EDD's description and schematic...Neal :: :: :: ::Sir Neal: :: :: :: ::Okely-Dokely. . . .with The first two sets off the rectifiers DC output, being the most suspect. :: :: :: ::73's de Edd :: :: :: :::::Good Morning EDD, :::: ::::I must confess that I have CAREFULLY rewired the speaker. It had to be done. I will certainly benefit from the schematic you sent me. I have one already but not pinpointing the capacitors like you have done. :::: ::::I'm awaiting capacitors then I will scrutinize and apply what you've written. :::: ::::2uf caps at 600vdc are hard to come by. I've ordered 10 1uf and there on the way. I'll just put a couple in parallel for the 2uf's. Appreciate the input...Neal ::::: ::::: ::::: Sir Neal: ::::: ::::: ::::: :::::Dragging tuning condenser plate. . . tsk. . .tsk. . .BUT there were a BUNCH of potential candidates ! ! ! ::::: ::::: ::::: :::::Your main filters of interest on that set are shown in incremental order. . .with the #1 unit being the most critical, and :::::progressively on down the numerical line. Probably no fault with the [ORANGE] resonating capacitor unless it has opened up. :::::Can we also assume that none of the speaker / output transformer wiring has been messed with. . .I mention this because :::::the design of the AF output circuitry design of this set varies from the norm. ::::: ::::: :::::Herein is the difference: ::::: ::::: :::::One usually sees the AF output transformer receiving its swinging AF feed from the plate of the output transformer and :::::coupling on to the speaker via its secondary low Z winding. (Your set merely has an extra output tube in parallel) ::::: :::::NOW here is the real difference in your set. . .it is double dipping. . .look at the plate circuitry referencing of the plate line :::::highlighted in [BLUE] and see the line coming down and ending up at the speaker field coil winding. ::::: :::::Normally one sees the field coil winding used solely for the magnetizing of the electromagnet core in the speaker, and for :::::filtering action in the power supply, not so in this case. ::::: :::::That winding is receiving the AF signal from the plate , just as an output transformer normally would, and its magnet field :::::strength is varying in unison with the audio strength and content. Its usual / additional filter choke function is not necessary :::::here, since that is fully taken care of by the hefty 15 henry choke down there to the left along with its accompanying pi filter :::::network. ::::: :::::Now, re-examine the plate feed and you see at the broken [BLUE] feed line, that it is additionally capacitively coupling [5] its :::::AC audio component to the output transformer, with the total audio AC ground path then being completed via capacitor [6] :::::wider broken [BLUE] line. ::::: :::::NOW with that varying magnet field strength of the speaker working against the normal magnetic field produced by the :::::voice coil winding, one can get more than the normal excursion of the speaker cone. :::::Unless you might have incurred a phase reversal between the two fields, that is why I asked about that associative wiring, :::::merely rapid reversing of ONE pair of the leads will confirm, when comparing the two produced volume levels. ::::: ::::: ::::: ::::: ::::: ::::: ::::: :::::73's de Edd ::::: ::::: ::::: ::::: :::::

::::: ::::: :::::CLARIFIED BRUNSWICK #15. . . . . . MARK-UP SCHEMATIC : ::::: ::::: ::::: ::::: ::::: ::::: :Now there's a volume control the likes of which I've not seen before. :Lewis :::::

Vol-you-me control via degree of RF coupling. 73's de Edd

::::: ::::: ::::: ::::: ::::: ::::: :::::My Caps are in. Not in the radio but they have arrived. I've pulled the entire capacitor block out of the set. It's a solid mass of, I don't know what you would call it, but all the capacitor leads go in one side of this big brick of substance. It's about 3 X 5 X 4 inches. Amazingly all of the capacitors are still pretty close to the right capacitance. So I'm hoping they were leaking. I am counting on this to take care of my background hum...I'm studying EDD's description and schematic...Neal :: :: :: ::Sir Neal: :: :: :: ::Okely-Dokely. . . .with The first two sets off the rectifiers DC output, being the most suspect. :: :: :: ::73's de Edd :: :: :: :::::Good Morning EDD, :::: ::::I must confess that I have CAREFULLY rewired the speaker. It had to be done. I will certainly benefit from the schematic you sent me. I have one already but not pinpointing the capacitors like you have done. :::: ::::I'm awaiting capacitors then I will scrutinize and apply what you've written. :::: ::::2uf caps at 600vdc are hard to come by. I've ordered 10 1uf and there on the way. I'll just put a couple in parallel for the 2uf's. Appreciate the input...Neal ::::: ::::: ::::: Sir Neal: ::::: ::::: ::::: :::::Dragging tuning condenser plate. . . tsk. . .tsk. . .BUT there were a BUNCH of potential candidates ! ! ! ::::: ::::: ::::: :::::Your main filters of interest on that set are shown in incremental order. . .with the #1 unit being the most critical, and :::::progressively on down the numerical line. Probably no fault with the [ORANGE] resonating capacitor unless it has opened up. :::::Can we also assume that none of the speaker / output transformer wiring has been messed with. . .I mention this because :::::the design of the AF output circuitry design of this set varies from the norm. ::::: ::::: :::::Herein is the difference: ::::: ::::: :::::One usually sees the AF output transformer receiving its swinging AF feed from the plate of the output transformer and :::::coupling on to the speaker via its secondary low Z winding. (Your set merely has an extra output tube in parallel) ::::: :::::NOW here is the real difference in your set. . .it is double dipping. . .look at the plate circuitry referencing of the plate line :::::highlighted in [BLUE] and see the line coming down and ending up at the speaker field coil winding. ::::: :::::Normally one sees the field coil winding used solely for the magnetizing of the electromagnet core in the speaker, and for :::::filtering action in the power supply, not so in this case. ::::: :::::That winding is receiving the AF signal from the plate , just as an output transformer normally would, and its magnet field :::::strength is varying in unison with the audio strength and content. Its usual / additional filter choke function is not necessary :::::here, since that is fully taken care of by the hefty 15 henry choke down there to the left along with its accompanying pi filter :::::network. ::::: :::::Now, re-examine the plate feed and you see at the broken [BLUE] feed line, that it is additionally capacitively coupling [5] its :::::AC audio component to the output transformer, with the total audio AC ground path then being completed via capacitor [6] :::::wider broken [BLUE] line. ::::: :::::NOW with that varying magnet field strength of the speaker working against the normal magnetic field produced by the :::::voice coil winding, one can get more than the normal excursion of the speaker cone. :::::Unless you might have incurred a phase reversal between the two fields, that is why I asked about that associative wiring, :::::merely rapid reversing of ONE pair of the leads will confirm, when comparing the two produced volume levels. ::::: ::::: ::::: ::::: ::::: ::::: ::::: :::::73's de Edd ::::: ::::: ::::: ::::: :::::

::::: ::::: :::::CLARIFIED BRUNSWICK #15. . . . . . MARK-UP SCHEMATIC : ::::: ::::: ::::: ::::: ::::: ::::: :Now there's a volume control the likes of which I've not seen before. :Lewis :::::

I've got all this cool radio stuff to do and the wife has honey-do's all the way through memorial day weekend. So it looks like it will be a while before I can get back to you.

Yeah, the volume control is totally mechanical. As you turn the knob, a metal strap goes in and out of the tuning condenser, touching nothing. It is hooked on the end, however, if my memory serves me right, causing a bending in and out effect...Neal

:::::: :::::: :::::: :::::: :::::: :::::: ::::::My Caps are in. Not in the radio but they have arrived. I've pulled the entire capacitor block out of the set. It's a solid mass of, I don't know what you would call it, but all the capacitor leads go in one side of this big brick of substance. It's about 3 X 5 X 4 inches. Amazingly all of the capacitors are still pretty close to the right capacitance. So I'm hoping they were leaking. I am counting on this to take care of my background hum...I'm studying EDD's description and schematic...Neal ::: ::: ::: :::Sir Neal: ::: ::: ::: :::Okely-Dokely. . . .with The first two sets off the rectifiers DC output, being the most suspect. ::: ::: ::: :::73's de Edd ::: ::: ::: ::::::Good Morning EDD, ::::: :::::I must confess that I have CAREFULLY rewired the speaker. It had to be done. I will certainly benefit from the schematic you sent me. I have one already but not pinpointing the capacitors like you have done. ::::: :::::I'm awaiting capacitors then I will scrutinize and apply what you've written. ::::: :::::2uf caps at 600vdc are hard to come by. I've ordered 10 1uf and there on the way. I'll just put a couple in parallel for the 2uf's. Appreciate the input...Neal :::::: :::::: :::::: Sir Neal: :::::: :::::: :::::: ::::::Dragging tuning condenser plate. . . tsk. . .tsk. . .BUT there were a BUNCH of potential candidates ! ! ! :::::: :::::: :::::: ::::::Your main filters of interest on that set are shown in incremental order. . .with the #1 unit being the most critical, and ::::::progressively on down the numerical line. Probably no fault with the [ORANGE] resonating capacitor unless it has opened up. ::::::Can we also assume that none of the speaker / output transformer wiring has been messed with. . .I mention this because ::::::the design of the AF output circuitry design of this set varies from the norm. :::::: :::::: ::::::Herein is the difference: :::::: :::::: ::::::One usually sees the AF output transformer receiving its swinging AF feed from the plate of the output transformer and ::::::coupling on to the speaker via its secondary low Z winding. (Your set merely has an extra output tube in parallel) :::::: ::::::NOW here is the real difference in your set. . .it is double dipping. . .look at the plate circuitry referencing of the plate line ::::::highlighted in [BLUE] and see the line coming down and ending up at the speaker field coil winding. :::::: ::::::Normally one sees the field coil winding used solely for the magnetizing of the electromagnet core in the speaker, and for ::::::filtering action in the power supply, not so in this case. :::::: ::::::That winding is receiving the AF signal from the plate , just as an output transformer normally would, and its magnet field ::::::strength is varying in unison with the audio strength and content. Its usual / additional filter choke function is not necessary ::::::here, since that is fully taken care of by the hefty 15 henry choke down there to the left along with its accompanying pi filter ::::::network. :::::: ::::::Now, re-examine the plate feed and you see at the broken [BLUE] feed line, that it is additionally capacitively coupling [5] its ::::::AC audio component to the output transformer, with the total audio AC ground path then being completed via capacitor [6] ::::::wider broken [BLUE] line. :::::: ::::::NOW with that varying magnet field strength of the speaker working against the normal magnetic field produced by the ::::::voice coil winding, one can get more than the normal excursion of the speaker cone. ::::::Unless you might have incurred a phase reversal between the two fields, that is why I asked about that associative wiring, ::::::merely rapid reversing of ONE pair of the leads will confirm, when comparing the two produced volume levels. :::::: :::::: :::::: :::::: :::::: :::::: :::::: ::::::73's de Edd :::::: :::::: :::::: :::::: ::::::

:::::: :::::: ::::::CLARIFIED BRUNSWICK #15. . . . . . MARK-UP SCHEMATIC : :::::: :::::: :::::: :::::: :::::: :::::: ::Now there's a volume control the likes of which I've not seen before. ::Lewis ::::::

Well, I've started putting the caps back in. I have 2 in successfully. I am having a hard time determining what goes where, even with the schematic, because all the old caps just reside inside of this big block of waxlike substance. I can't see how they are hooded. only the leads stick out. I can measure capacitance from wire to wire, and I have the wires labeled as to which terminal they came off. But still I struggle. I'm tempted to open up the big block but I won't do that because it has July 17, 1930 stamped on it. Well, anyway, that is where I'm at up to this point.

I got somewhat traumatized when I developed a high pitched background tone until I found out that it was present on all my am radios. Still don't know what it is. I've traced back through electronic gadgets I've worked on to see if I could find the culprit...Neal

::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::My Caps are in. Not in the radio but they have arrived. I've pulled the entire capacitor block out of the set. It's a solid mass of, I don't know what you would call it, but all the capacitor leads go in one side of this big brick of substance. It's about 3 X 5 X 4 inches. Amazingly all of the capacitors are still pretty close to the right capacitance. So I'm hoping they were leaking. I am counting on this to take care of my background hum...I'm studying EDD's description and schematic...Neal :::: :::: :::: ::::Sir Neal: :::: :::: :::: ::::Okely-Dokely. . . .with The first two sets off the rectifiers DC output, being the most suspect. :::: :::: :::: ::::73's de Edd :::: :::: :::: :::::::Good Morning EDD, :::::: ::::::I must confess that I have CAREFULLY rewired the speaker. It had to be done. I will certainly benefit from the schematic you sent me. I have one already but not pinpointing the capacitors like you have done. :::::: ::::::I'm awaiting capacitors then I will scrutinize and apply what you've written. :::::: ::::::2uf caps at 600vdc are hard to come by. I've ordered 10 1uf and there on the way. I'll just put a couple in parallel for the 2uf's. Appreciate the input...Neal ::::::: ::::::: ::::::: Sir Neal: ::::::: ::::::: ::::::: :::::::Dragging tuning condenser plate. . . tsk. . .tsk. . .BUT there were a BUNCH of potential candidates ! ! ! ::::::: ::::::: ::::::: :::::::Your main filters of interest on that set are shown in incremental order. . .with the #1 unit being the most critical, and :::::::progressively on down the numerical line. Probably no fault with the [ORANGE] resonating capacitor unless it has opened up. :::::::Can we also assume that none of the speaker / output transformer wiring has been messed with. . .I mention this because :::::::the design of the AF output circuitry design of this set varies from the norm. ::::::: ::::::: :::::::Herein is the difference: ::::::: ::::::: :::::::One usually sees the AF output transformer receiving its swinging AF feed from the plate of the output transformer and :::::::coupling on to the speaker via its secondary low Z winding. (Your set merely has an extra output tube in parallel) ::::::: :::::::NOW here is the real difference in your set. . .it is double dipping. . .look at the plate circuitry referencing of the plate line :::::::highlighted in [BLUE] and see the line coming down and ending up at the speaker field coil winding. ::::::: :::::::Normally one sees the field coil winding used solely for the magnetizing of the electromagnet core in the speaker, and for :::::::filtering action in the power supply, not so in this case. ::::::: :::::::That winding is receiving the AF signal from the plate , just as an output transformer normally would, and its magnet field :::::::strength is varying in unison with the audio strength and content. Its usual / additional filter choke function is not necessary :::::::here, since that is fully taken care of by the hefty 15 henry choke down there to the left along with its accompanying pi filter :::::::network. ::::::: :::::::Now, re-examine the plate feed and you see at the broken [BLUE] feed line, that it is additionally capacitively coupling [5] its :::::::AC audio component to the output transformer, with the total audio AC ground path then being completed via capacitor [6] :::::::wider broken [BLUE] line. ::::::: :::::::NOW with that varying magnet field strength of the speaker working against the normal magnetic field produced by the :::::::voice coil winding, one can get more than the normal excursion of the speaker cone. :::::::Unless you might have incurred a phase reversal between the two fields, that is why I asked about that associative wiring, :::::::merely rapid reversing of ONE pair of the leads will confirm, when comparing the two produced volume levels. ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::73's de Edd ::::::: ::::::: ::::::: ::::::: :::::::

::::::: ::::::: :::::::CLARIFIED BRUNSWICK #15. . . . . . MARK-UP SCHEMATIC : ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::Now there's a volume control the likes of which I've not seen before. :::Lewis :::::::

Now I have all the caps replaced. I have no background hum. Which was my intention. But I have developed a new problem that I'm unable to get around. I've studied all Edd has told me. I'll be the first to admit that Edd is so knowledgeable that he goes over my head at times. But I've tried my best to understand him. Now my problem is that I've lost all my stations above about 800KC and the ones below are not as strong as before. It has plenty of volume and it tunes in the noise at places on the dial that you know are stations but all I get is loud noise. Then the noise tunes out as you move the dial and then back in on the next station. Can you help me identify the cause of my problem? Edd...anyone seen this before?...Neal

I have all that disruptive source equipment plugged into my bench. I have a dremmel charger, a camcorder charger, soldering iron, 2 compters, dewalt drill charger, and much more stuff.

about a month ago I discovered that I had a high pitched hum when off station on all the radios in the house. That made me wonder.

You don't think that I have miswired one of the caps that I have replaced?

that will be fun isolating all my noise makers. Thanks for the idea. I'm getting kind of frustrated with this ol Brunswick.

On another note. Today I acquired a Thomas A. Edison sound 'reproducer'. It's really cool. Totally mechanical. Not a wire to be found in it. It's model number C150. You wouldn't happen to know what year it was made in would you. I'm thinking about 1918 to 1922 or so...Neal Oh and it's in pretty darn good shape...Neal again.

:

: : : : : : : : : : : :How come. . .?. . .. I want to suspicion an interfering source. With the noise blanketing the spectrum, except on the tuning threshold point where you are about to tune into a station, that is being at the same signal level as the interference and :then starting to abate, until you eventually get right on the station. Then, if you happen to tune on past the station, the weaker background interference will reassume itself. : : : :There ever so many more interference sources nowadays, hidden away in subtle places that you typically would not expect. : :In the olden days of AC plug installed “Wall Warts” , expect to find an iron core transformer inside and the unit either putting out raw AC to be sent to the device of use and processed or sometimes, the Wart housing including a bridge rectifier :and its adjunct filtering capacitors to send out DC to the unit of use. : : :I now fully expect units to be incorporating a much more efficient line operated power supply that merely uses a wisp of power by the unit sampling power demand and ramping up as any demands for increase are detected. :These units, being used with Cell phone chargers, electric toothbrushes, I –Pod and Blackberry chargers, slave speaker systems for I-Pods, cam corder chargers, etc. Internal display power supplies in microwave ovens, electric coffee pots. . . . ad infinitum. : : :Its common to use an encapsulated IC with 8 leads , built up in an ~3/8 x 3/8 in sq plastic housing that incorporates all of the control-driver-regulation electronics WITH a power FET switching transistor also included in the same package. : :That unit. . .according to design. . . could be idling at ~60-80-120 Khz and then will throw out upper harmonics of those frequencies all over the broadcast band. The interference strength, then being in accordance to the proximity to those :devices. : : : :Since you already confirm a like effect to other receivers, being used in that same receive location, first thing that I would be doing would be to get assistance in doing a circuit breaker sweep of your AC line supply feeds. Considering that you are :off by yourself in a sole residence and have no common neighbors wall to wall with you or that sharing the same line power transformer feed. : : :Initially have a trouble light, with its common extension cord line plugged into an another room, and its end with the light, then being in your room with the receiver. : :Then have the breakers singly flipped to find that sole branch that your radio is operating from, and also note if the trouble light happened to have went OFF in the prior sweep of breakers. If so, that confirms it not being on your radios supply line. :THEN have All of the breakers off, excepting the one that your radio is operating from. If the interference was lost then it’s the tracking down of the feed line where the interfering object is connected into. :Should the interference have been omnipresent, thru all circuit breaker disrupts, then the trouble light is brought over nearby and the radio plugged into its side outlet and then the breaker that fed the trouble light is reinstated at its breaker and then the breaker that initially fed the :radio is tripped and that would confirm if any bench line connections are the source of your interference. : : : :Yet another interference source seeker is a shirt pocket sized. . .. or small. .. ..AM transistor receiver, whereupon it can be carried around and moved into the vewy close proximity of suspects. OR it’s built in ferrite bar antenna can be uses as a direction finder. A signal will peak if broadside to its bar antenna inside of the unit, or will null if either of the bars ends are pointing at the :signal, needless to say, that latter, is the best and most differentiating manner of its use. : : :BTW. . .loooooong . . .before GPS and even the alternate of using a magnetic compass, my navigational choice out in the sticks was the carrying of an AM pocket radio and then nulling into and then azimuth angle interpolating against local and quasi-suburban AM radio stations. : : :Particularly two of them, one of which was 60 miles north of home and the other being 40 miles east of home, AND the home station which WAS sited in the home town. : : : : : : :73's de Edd : : : : :

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