625A_A-P

This tube is of the "Two in One" style made by A-P but designed by their employee, Henry K Huppert. He applied for a patent on the tube on June 11, 1924 and patent no 1,597,893 was issued to him on August 31, 1926 It is used as an amplifier. The anodes and grids are connected to the normal base positions but the filament is centre tapped with a soldered connection for this at the rim of the base shell. Early versions used the shaw "Standard Base" and later tubes had porcelain insulation in the base. Most bases were nickel plated but some were unplated brass.

Branding of thes tubes is very confusing. On one side of the base are the words: A-P Radio Labs ; Patent Pending and on the other side 6 volts .25 amps. In some cases the description "amplifier" was printed on this side as well. In other cases the only way to identify the tube is from the data sheet which came in the box with the tube. This showed that the tube was either an amplifier or detector type.

625A_A-P: Fin Stewart Fin Stewart	Just Qvigstad

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