GU-50

The GU-50 (ГУ-50 rus.) is a high-power Soviet beam power pentode designed for use as a 50W linear amplifier at frequencies up to 120MHz. It is a Soviet copy of the Telefunken LS-50 high-power pentode, developed via reverse engineering based on components from German military radio equipment captured during World War II.

The tube features a non-standard 8-pin base and a metal cap—electrically isolated from the internal elements—topped with a plastic handle; this handle facilitates removing the tube from its socket, especially when hot. Its operating position is vertical. The GU-50 is popular among radio amateurs building audio amplifiers as an affordable and simple option for achieving high output power.

Near equivalent tube: FU-50, LS-50.

• Stamp of technical control department of the manufacturer ” ОТК “

Technical specifications: (at Un=12.6 V, Ua=0.8 kV, Uc2=0.25 kV, Uc3=0V, Ia=50 mA).

• Filament current: 0.705 ± 0.065A
• Anode current: not less than 50mA
• 1st grid current: no more than 8mA
• 2nd grid current: no more than 5mA
• 1st grid reverse current (at Ic2=15mA): no more than 15µA
• 3rd grid reverse current (at Ic2=15 mA): no more than 25µA
• Leakage current between cathode and heater: no more than 100µA
• Permeability of the 1st grid relative to the 2nd grid: 19 ± 3%
• The voltage of the 1st grid at the operating point is negative: 40 ± 10V
• 3rd grid turn-off voltage negative: 205 ± 55V
• Slope: 4 ± 1mA/V
• Oscillatory power:
  – at Un=12.6 V not less than 60W
  – at Un=10.8V not less than 52W

Limiting operational characteristics:

• Filament voltage: 10.8 – 14.5V
• Anode voltage: 1kV
• Voltage of the 2nd grid: 0.25kV
• Voltage between cathode and heater: 200V
• Anode current: 230mA
• Power dissipated by the anode: 40W
• Power dissipated by the 2nd grid: 5W
• Power dissipated by the 1st grid: 1W

Operating time not less than 1750 hours.