Pictures:

Details:
The Svetlana GP-5 (ГП-5) is a glass-envelope beam power triode intended for use as a shunt regulator or pulse modulator in high-voltage systems. It features anode operating voltage of 30 kV and a plate dissipation of 37.5 watts. Originally intended for color-TV voltage stabilization, the GP-5 is similar to the Telefunken ED500 and may be used to retrofit equipment which uses the American type 6BK4 or other high-voltage beam triodes.
Military equipment with “OTK” mark. Near equivalent: ED500 and 6BK4. The tube is manufactured by the Svetlana, St. Peterburg, Russia.

Datasheet:
General characteristics:
Name: GP5
Cathode: oxide-coated, unipotential
Voltage (AC or DC), V: 6.3 (± 0.6)
Current, mA: 210 (± 20)
Heater-cathode voltage, peak, V: ±200
Amplification factor (nominal): 2750
Transconductance (nominal), uS: 700
Interelectrode capacitances (typical), with cathode grounded:
– Input 4.0 pF
– Output 1.5 pF
– Feedback 0.1 pF

Mechanical characteristics:
Base standard magnoval, glass button
Socket Svetlana SK509 or similar
Anode cap approx. 3/8 in (9 mm) diameter
Anode connector same as 6BK4 or 807
Operating position Any (vertical for convection cooling)
Nominal dimensions:
– Height of glass envelope 100 mm (3 7/8 in)
– Diameter of glass envelope 46 mm (1 3/4 in)
– Overall height 125 mm (4 7/8 in.)
Net weight: 115g

Maximum ratings:
Anode voltage: 30KV
Anode dissipation: 37.5W
Anode current, continuous: 2mA
Grid voltage: -450V
Maximum grid-circuit resistance: 3 MOhms
Envelope temperature: 250C

Links:
Radiomuseum
Russian tubes