5687

5687 has no equivalent designation confirmed by the archive. Completed sales put the typical price at $32.91 per tube.

The 5687 is a double triode, containing two electrically independent triode elements within a single envelope.

## Construction

The tube features a reinforced internal structure designed for high mechanical robustness and operating reliability. It has oxide cathodes and indirect heating. The 5687 can be mounted in any position. The filament can be operated at 12.6 V or 6.3 V ±10%, drawing 0.45 A or 0.9 A respectively. The filament is center-tapped on pin 8.

The pinout is as follows: anode element 2 on pin 1, grid element 2 on pin 2, cathode element 2 on pin 3, filament on pins 4 and 5, cathode element 1 on pin 6, grid element 1 on pin 7, and anode element 1 on pin 9.

## Ratings

The maximum anode voltage is 300 V. Anode dissipation is 4.2 W per element, with a total of 7.5 W for both elements. Maximum cathode current is 65 mA, and maximum grid current is 6.0 mA. The maximum grid resistance is 1.5 MΩ. The maximum voltage between cathode and filament is ±100 V. Maximum bulb temperature is 220 °C.

## Characteristics

At Vf = 6.3 V, Va = 120 V, Vg = -2 V, and Rk = 0, the amplification factor per element is between 15 and 21, the anode current per element is between 27 mA and 45 mA, and the transconductance per element is between 8 mA/V and 14 mA/V. Under the same conditions, the datasheet gives a vibratory voltage of 250 mV maximum with an acceleration of 10 g at 50 Hz.

Typical values are also given at other anode voltages: at Va = 120 V, the amplification factor is 18.5, internal resistance is approximately 1700 Ω, transconductance is 11 mA/V, and anode current is 36 mA; at Va = 180 V, the amplification factor is 17.5, internal resistance is approximately 2100 Ω, transconductance is 8.25 mA/V, and anode current is 21 mA; at Va = 250 V, the amplification factor is 16.5, internal resistance is approximately 3000 Ω, transconductance is 5.5 mA/V, and anode current is 12.5 mA.

The datasheet gives grid-to-anode capacitance per element as 4.0 pF maximum without external shielding, input capacitance per element as 4.0 pF, output capacitance as 0.6 pF for element 1 and 0.5 pF for element 2, filament-to-cathode capacitance as 8.0 pF, approximate grid-to-grid capacitance as 0.025 pF, and approximate anode-to-anode capacitance as 0.75 pF.

With Vf = 6.3 V and Vfk = ±100 V, the filament-to-cathode current is 10 μA maximum. Interelectrode insulation resistance is 100 MΩ minimum with 100 V between grid and other electrodes, and 50 MΩ after 500 hours of life; it is also 100 MΩ minimum with 300 V between anode and other electrodes, and 50 MΩ after 500 hours of life. Maximum reverse grid current is 3 μA at Vf = 6.5 V, Va = 120 V, Vg = -2 V, Rg = 100 kΩ, Rk = 0.

## Applications

The 5687 is suited to various amplifier circuits, especially applications needing two electrically independent triode elements. Its low internal resistance allows its use as a regulator tube in stabilized power supplies. It was specially intended for military and professional equipment, developed for the Service Technique des Télécommunications de l'Air. The Compagnie Générale de T.S.F. datasheet notes that the tube was formerly manufactured by Société Française Radio-Électrique, merged with C.S.F.

Per-tube prices from completed sales, 2026-08-27 to 2026-09-15. Matched pairs and quads are divided out. See the price index for how these move over time.

Original manufacturer datasheets for 5687, hosted by Frank Philipse's Electron Tube Data sheets.

Documents held here and used to write this page.

• **DOUBLE TRIODE** 5687