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What a gorgeous chassis, even after 70 years! Here is a close up the SW-3 chassis with the cabinet removed. The back of the cabinet is
completely removed, then the chassis is detached from the cabinet and slid out the rear of the cabinet. The photo shows the chassis with the tubes and coils installed. The front of the chassis is towards the bottom facing you. The
RF amplifier coil and tube (6C6) are located on the lower left. The detector coil and tube (6C6) are located on the lower right. The dual ganged tuning capacitor is in the center and the audio coupling transformer is located along the center rear of
the chassis. The tuning capacitor is a dual capacitor but a single assembly which suggests its a Model II. |
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This photo shows the chassis without the tubes or coils. The white socket in the lower left is the rf amplifier coil socket. The white
socket in the upper left is the rf amplifier tube socket. The white socket on the lower right is the detector tube socket. The white socket on the upper right is the detector coil socket. In the upper right corner is a brown tube socket for the audio
amplifier tube. Note that the coil sockets and the rf amplifier and detector tube sockets are made of
porcelain, a high performance tube socket, so even in the minimalist radio, National used top quality high reliability components. I notice they
didn't use a porcelin socket for the audio amplifier tube socket in the upper right corner. Along the back of the chassis (photo top) is a series of screw terminals. The pair on the upper right side is for the head phones. The terminal unscrews
allowing the user to insert the headphone pin and then tighten the screw. The pair on the upper left is the a Along the lower front edge of the chassis you can see the rf tune capacitor, horizontal volume control pot and knob, and the regeneration potentiometer. |
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This photo shows the left side of the chassis. This view shows the antenna and ground terminals on the lower left side. The assembly
around the rf amplifier tube is for a tube shield which is not shown. |
 Click on the thumbnail photo to bring up a large picture. Here is a close up of the underside of the chassis. Not a lot of parts is it. The "front" is up, the "back" is down. Oops, you can see a couple of temporary tacked on troubleshooting fixes. Other than my tacked on resistor which fixes an open R7 resistor section, and the tacked on wire/resistor in the upper left which fixes a previous owner wiring modification, the SW-3 components are well secured to the chassis for stability. |