6F5

6F5 is also designated 6F5GT. Completed sales put the typical price at $12.31 per tube.

The 6F5 is a general-purpose high-mu triode, available in the 6F5, 6F5G, and 6F5GT forms as a glass tube with a small octal base; the 6F5GT version has a coated unipotential cathode and a T-90 bulb.

Construction

The 6F5GT is a cathode-type high-mu triode in a glass envelope with a small octal base. The 6F5GT may be used interchangeably with the 6F5G glass tube where conditions permit a larger size. The 6F5GT has a coated unipotential cathode. The JETEC datasheet specifies that the mounting position is any.

Ratings

The Tung-Sol datasheet gives the heater voltage as 6.3 volts AC or DC and the heater current as 0.3 ampere. The maximum plate voltage is 300 volts, as given by both the Tung-Sol and JETEC datasheets. The JETEC datasheet also gives maximum peak positive voltages of 2.0 volts for grid No. 1 to plate, 6.0 volts for grid No. 1 to cathode, and 12.0 volts for plate to cathode.

Operating Characteristics

The amplification factor is 100 at plate voltages of both 100 volts and 250 volts, per the Tung-Sol datasheet. The JETEC datasheet provides typical operating conditions at 100 volts plate voltage, -1.0 volts grid voltage, with 85,000 ohms plate resistance, 1150 µmhos transconductance, and 0.4 mA plate current. At 250 volts plate voltage and -2.0 volts grid voltage, the JETEC datasheet gives 66,000 ohms plate resistance, 1500 µmhos transconductance, and 0.9 mA plate current. The Hytron datasheet lists voltage amplification of 52 to 56 at 250 volts plate supply voltage with a grid voltage of -1.3 volts, and 51 to 60 at 250 volts plate supply voltage with a grid voltage of -1.5 volts.

Application Notes

The Tung-Sol datasheet states that the 6F5, 6F5G, and 6F5GT are designed for service as high gain resistance coupled amplifiers in AC and AC-DC operated receivers. The Hytron datasheet notes that voltage between heater and cathode should be kept at a minimum if direct connection is not possible. For characteristic curves, the JETEC datasheet refers to the type 6780.

Equivalence is asserted only where the archive's own literature states it directly, in at least 40 separate documents. Tubes that merely substitute in some circuits are not listed here.

Per-tube prices from completed sales, 2026-07-14 to 2026-09-23. Matched pairs and quads are divided out. See the price index for how these move over time.

Original manufacturer datasheets for 6F5, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

• JETEC DATA JOINT ELECTRON TUBE ENGINEERING COUNCIL COMMITTEE ON RECEIVING TUBES (filed under 6F5GT)
• TUNG-SOL

2 further designations appear alongside 6F5 in the literature but below the evidence threshold used here, so they are not listed as equivalent.