Tough mil. spec full wave rectifier tubes manufactured in Russia by Sovtek in the 1970’s. These 8 pin glass octal based tubes come with huge steel plates, two thick mica spacers, and top getters. They can easily handle up to 400 plate volts at currents up to 250 mA. They are marked 5U4M OTK with various other codes. Photo is typical of available stock.
Data sheet
Tough mil. spec full wave rectifier tubes manufactured in Russia by Sovtek in the 1970’s. These 8 pin glass octal based tubes come with huge steel plates, two thick mica spacers, and top getters. They can easily handle up to 400 plate volts at currents up to 250 mA. They are marked 5U4M OTK with various other codes. Photo is typical of available stock.