7587 — Special-Quality Sharp-Cutoff Nuvistor Tetrode
An industrial all-metal-and-ceramic miniature tetrode for high-transconductance amplification, low-voltage operation, and mechanically demanding electronic equipment.
Overview
The 7587 is a sharp-cutoff Nuvistor tetrode for general-purpose industrial amplifier applications. RCA identifies it as a sharp-cutoff, high-transconductance Nuvistor, while Lorenz describes a steep-slope universal tetrode suitable for relatively low operating voltages. Philips documents the tube as a special-quality, shock- and vibration-resistant tetrode.
Its characteristic design combines a control grid, screen grid, and plate with an indirectly heated coated cathode in a compact metal-ceramic structure. The published operating point uses 125 V plate supply, 50 V screen supply, and approximately 10 mA plate current, with 10.6 mA/V transconductance.
Construction, Basing, and Heater
The 7587 uses a metal-shell MT4 envelope with a ceramic cylinder, a skirted miniature plate cap, and an E5-65 ceramic-wafer Nuvistor base. The RCA basing designation is 12AS. The tube requires a Nuvistor socket and may be mounted in any position.
The manufacturer pin diagram identifies pin 2 as screen grid, pin 4 as control grid, pin 8 as cathode, and pins 10 and 12 as heater. The plate is brought to the top cap. Other base positions include internal connections and a designated do-not-use contact, and must be interpreted according to the indexed manufacturer's basing diagram.
The heater may be powered by AC or DC.
Typical Class A1 Amplifier Characteristics
The high plate resistance and relatively high transconductance are characteristic of the tube's tetrode operating behavior. RCA provides plate-current and transfer-characteristic curves to illustrate the effect of control-grid bias and screen-grid voltage.
Philips gives production-design ranges of 8.5–11.5 mA plate current, 1.8–3.6 mA screen current, and approximately 9–12.2 mA/V transconductance at the defined test condition.
Industrial Maximum Ratings
The plate and screen supply-voltage limits are distinct from the maximum electrode voltages. The higher 330 V supply figures are not unrestricted continuous plate or screen operating voltages.
Interelectrode Capacitances
Philips lists a slightly different nominal grid-to-plate capacitance of approximately 0.01 pF. The exceptionally small control-grid-to-plate capacitance is significant for reducing direct input-output feedback in an amplifier.
Reliability and Special-Quality Tests
The RCA industrial sheet specifies extensive sample-lot tests, including 1,000 g impact shock, 2.5 g fatigue vibration for 48 hours at 60 Hz, vibration-induced output-noise testing, low-pressure breakdown testing, heater cycling, shorts and continuity testing, and life-performance evaluation.
RCA's variable-frequency vibration test specifies ≤35 mV RMS output over 50–6,000 Hz and ≤500 mV over 6,000–15,000 Hz under the stated 1 g test arrangement.
The low-pressure breakdown test applies 240 V RMS between plate and other electrodes under simulated altitudes up to 100,000 feet. RCA also specifies a minimum 2,000 heater on/off cycles in its test procedure.
Production qualification includes early-hour stabilization, 100-hour life testing, and 1,000-hour performance evaluation. These tests describe industrial quality control rather than a single unconditional guaranteed service life.
Manufacturer Documentation
Lorenz, RCA, and Philips consistently describe a sharp-cutoff, high-transconductance tetrode with 6.3 V / 150 mA heater, 125 V plate-supply characteristic point, and 10.6 mA/V nominal transconductance. Their documents differ in the depth of industrial reliability and production-tolerance data.
The Philips source is a special-quality sheet originally dated 1962, despite its later archive/catalog label. The RCA detailed industrial documentation provides the fullest mechanical and qualification information.
Technical Summary
The 7587 is a 6.3 V / 150 mA sharp-cutoff industrial Nuvistor tetrode with 12AS basing, a top-cap plate connection, 10.6 mA/V transconductance, approximately 200 kΩ plate resistance, and 2.2 W maximum plate dissipation.
Its high-slope characteristics, very low grid-to-plate capacitance, compact metal-ceramic construction, and extensive shock, vibration, altitude, and endurance testing distinguish it as a specialized industrial amplifier tube.
