6689

6689 is also designated E83F.

The 6689 is a pentode intended for use in telephone equipment, with a coated unipotential cathode and a design life exceeding 10,000 hours. It has a T6½ bulb and an E9-1 base, with a RETMA basing designation of 9RK. The tube can be mounted in any position.

Construction

The 6689 uses a coated unipotential cathode. The tube has a T6½ bulb and an E9-1 base. The RETMA basing designation is 9RK.

Ratings

The heater is rated at 6.3 volts, with a typical current of 0.300 amperes (minimum 0.285, maximum 0.315 amperes). The plate voltage rating is 210 volts, with a plate voltage without current rating of 550 volts and a plate dissipation rating of 2.1 watts. Grid No.2 has a voltage rating of 210 volts, a voltage without current rating of 550 volts, and a dissipation rating of 0.35 watts. The cathode current rating is 16 milliamperes. The grid No.1 circuit resistance rating with automatic bias is 1 megohm. The bulb temperature rating is 170°C.

Electrical Characteristics

Typical transconductance is 9000 micromhos (minimum 7800, maximum 10200). The amplification factor of grid No.2 with respect to grid No.1 is 34. Plate resistance is typically 0.5 megohm (minimum 0.3 megohm). Equivalent noise resistance (R.F.) is typically 750 ohms (maximum 1000 ohms), while the equivalent noise resistance (30–10,000 c/s) is 36,000 ohms. Negative grid No.1 bias at a plate current of 0.5 milliamperes is typically 3.0 volts (maximum 5.25 volts). Grid No.1 bias at grid No.1 current = +0.3 μA is −1.1 volts. Negative grid current with a grid series resistor of 0.1 megohm is 0.5 μA. Grid No.1 hum voltage with a grid leak of 0.5 megohm is typically 0.06 millivolts (maximum 0.5 millivolts).

Capacitances

Plate to all other elements capacitance is 3.6 μμF bogey (maximum 4.2 μμF). Grid No.1 to all other elements capacitance is 8.5 μμF bogey (maximum 9.2 μμF), and at a cathode current of 12.1 milliamperes, it is 11.3 μμF. Plate to grid No.1 capacitance is 0.015 μμF. Grid No.1 to heater capacitance is 0.15 μμF. Cathode to heater capacitance is 4.0 μμF. Radiation capacitance of the plate is 0.025 μμF, and that of grid No.1 is also 0.025 μμF.

Insulation and Heater-Cathode

Insulation between two electrodes is 20 megohms. Insulation between cathode and heater, with a voltage between heater and cathode of 100 volts, is 5 megohms. The heating time of the cathode is typically 13 seconds (range 8 to 20 seconds), and the cooling time is typically 12 seconds (range 7 seconds and above). For stable operation, the external resistance between heater and cathode should be restricted to values smaller than 20,000 ohms.

Life and End Points

To obtain a tube life of 10,000 hours, the datasheet specifies that for parallel supply of heaters, the maximum variations of the heater voltage should be less than ±5% (absolute limits), and for series supply, the maximum variation of the heater current should be less than ±1.5% (absolute limits). The end point of life is reached when the plate current has changed to 7.0 milliamperes, when the grid No.2 current has changed to 1.25 milliamperes, when the transconductance has changed to 6400 micromhos, or when the negative grid current has changed to 1.0 μA.

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.

Original manufacturer datasheets for 6689, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

• **PHILIPS** (filed under E83F)
• 6689