[mikethedruid]

I have been working on a very interesting National SW-54. As many of you probably know, this set has a chassis which is connected to one side of the line. It also has a steel housing which is connected to that chassis. This can pose a serious shock hazard. Someone has isolated the chassis from line on this unit using two 120V to 12V filament transformers. The first steps the line down from 120V to 12V for the filaments of the four remaining tubes in the set and the dial lamp. The second steps the 12V back up tp 120V, which then goes through a diode bridge to provide the B voltage to the set. The 35Z5 is eliminated, and the 50C5 us changed to a 12CU5/12C5. All four remaining tubes filament circuits are rewired in parallel as well as the dial lamp. Whoever did the work did an excellent job, very neat, with the filament wiring twisted and dressed right next to the chassis. I replaced the big firecracker four section electrolytic with four modern electrolytics of higher voltage rating and slightly higher capacity, and I replaced all the paper condensers. I then aligned the set. It actually works very well. It is a little deaf on the upper band, but that is fairly normal on such a set. I am quite pleased with it, and am going to keep it since it is such a rare bird. Here are some pictures of the underside of the chassis and the chassis top, as well as the schematics. Compare the pictures to how the set normally looks using the manual which you can find here   http://bama.edebris.com/manuals/national/sw54/   
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