03-26-2018, 12:51 AM
Murf;
The two red wires in the speaker cable are connected together at the plug, one goes to one side of the field coil the other goes to the output transformer center tap, the red and blue wire goes to the other side of the field coil. It looks like from the diagram that the speaker plug has four pins, two are closer together, the other two are further apart, the ones that are further apart go to the field coil and the center tap of the output transformer, or are there two fat pins and two thin pins like a tube socket? Why they chose to add a second red wire from the plug up to the output transformer only the manufacturer could explain, if I were wiring the speaker cable I would have eliminated one of the red wires and tied the O.T primary center tap and the one leg of the field coil together at the speaker, as it is I would leave it alone unless you have to replace the speaker cable. The two yellow wires go to the outside legs of the output transformer primary, the other end goes to the plug, and through the speaker plug socket to the plates of the 6F6 tubes.
On the voice coil side the way it works is that the voice coil should be connected in series with the hum bucking/neutralizing coil, if you copy the hookup between the O.T secondary on the old transformer exactly, and transfer those connections to the proper pair of taps on the O.T secondary you should be fine. To me it looks like one leg of that secondary connects to something other then the voice coil in the diagram on page 7 here: http://www.nostalgiaair.org/pagesbymodel...017120.pdf Is this the frame of the speaker? Is that what you were trying to ask me about? If so then one end of the hum bucking coil is connected to the speaker frame and through the frame to one end of the O.T secondary. In the instructions with your new O.T there should be something telling you which pair of taps to select on the secondary to match the tubes to the voice coil, since the service info doesn't give you the impedance of the voice coil I would use a pair of clip leads to try a few pairs using the table under 6F6s as a guide.
Regards
Arran
The two red wires in the speaker cable are connected together at the plug, one goes to one side of the field coil the other goes to the output transformer center tap, the red and blue wire goes to the other side of the field coil. It looks like from the diagram that the speaker plug has four pins, two are closer together, the other two are further apart, the ones that are further apart go to the field coil and the center tap of the output transformer, or are there two fat pins and two thin pins like a tube socket? Why they chose to add a second red wire from the plug up to the output transformer only the manufacturer could explain, if I were wiring the speaker cable I would have eliminated one of the red wires and tied the O.T primary center tap and the one leg of the field coil together at the speaker, as it is I would leave it alone unless you have to replace the speaker cable. The two yellow wires go to the outside legs of the output transformer primary, the other end goes to the plug, and through the speaker plug socket to the plates of the 6F6 tubes.
On the voice coil side the way it works is that the voice coil should be connected in series with the hum bucking/neutralizing coil, if you copy the hookup between the O.T secondary on the old transformer exactly, and transfer those connections to the proper pair of taps on the O.T secondary you should be fine. To me it looks like one leg of that secondary connects to something other then the voice coil in the diagram on page 7 here: http://www.nostalgiaair.org/pagesbymodel...017120.pdf Is this the frame of the speaker? Is that what you were trying to ask me about? If so then one end of the hum bucking coil is connected to the speaker frame and through the frame to one end of the O.T secondary. In the instructions with your new O.T there should be something telling you which pair of taps to select on the secondary to match the tubes to the voice coil, since the service info doesn't give you the impedance of the voice coil I would use a pair of clip leads to try a few pairs using the table under 6F6s as a guide.
Regards
Arran
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