01-05-2014, 04:08 PM
Victor;
Is the transformer an original equipment type? In my 40-201, it had been replaced by an after-market substitution. I believe all the Philco transformers had their actual part number stamped into the metal or somehow written on it to identify it. The replacement in my radio had significant ohm differences from CT to either end, yet it seems to work OK after recapping and phase splitter resistor replacements. Someone pointed out that the main issue is that the two halves of the primary windings have the same inductance value, whether or not the actual DC resistance is the same. That said, I think the plate voltages going to the two push-pull output tubes should be pretty nearly equal. So should the screen grid voltages. One thing that might make the voltages different to some extent would be if one or the other tube had a leaky coupling capacitor going to its grid.
The schematic referenced above shows that one side of the transformer should measure about 280 ohms from the CT and the other should read about 310 ohms from CT or about 590 ohms plate to plate of the two 6V6GT output tubes. The cathodes of both output tubes are tied to ground and the screen grids and the plate circuits to the two tubes both are tied to the same B+ source. If one of the tubes had shorted its plate to the suppressor grid/cathode circuit it could have burned 1/2 of the winding in the transformer. Do some checking with a volt meter and let us know the voltages you see on cathodes, grids, screen grids and plates of the two tubes. Make sure that there is -16VDC at the grids of both output tubes.
Joe
Is the transformer an original equipment type? In my 40-201, it had been replaced by an after-market substitution. I believe all the Philco transformers had their actual part number stamped into the metal or somehow written on it to identify it. The replacement in my radio had significant ohm differences from CT to either end, yet it seems to work OK after recapping and phase splitter resistor replacements. Someone pointed out that the main issue is that the two halves of the primary windings have the same inductance value, whether or not the actual DC resistance is the same. That said, I think the plate voltages going to the two push-pull output tubes should be pretty nearly equal. So should the screen grid voltages. One thing that might make the voltages different to some extent would be if one or the other tube had a leaky coupling capacitor going to its grid.
The schematic referenced above shows that one side of the transformer should measure about 280 ohms from the CT and the other should read about 310 ohms from CT or about 590 ohms plate to plate of the two 6V6GT output tubes. The cathodes of both output tubes are tied to ground and the screen grids and the plate circuits to the two tubes both are tied to the same B+ source. If one of the tubes had shorted its plate to the suppressor grid/cathode circuit it could have burned 1/2 of the winding in the transformer. Do some checking with a volt meter and let us know the voltages you see on cathodes, grids, screen grids and plates of the two tubes. Make sure that there is -16VDC at the grids of both output tubes.
Joe
