7586 — Special-Quality Medium-Mu Industrial Nuvistor Triode

A compact all-metal-and-ceramic receiving triode for low-noise amplification and stable oscillator service into the UHF region, with stringent industrial reliability testing.

Overview

The 7586 is a medium-mu, general-purpose Nuvistor triode intended for critical industrial amplifier and oscillator applications. RCA, Siemens, and Philips documentation emphasizes compact construction, low noise, stability, controlled characteristics, mechanical ruggedness, and operation across frequencies extending into the ultra-high-frequency (UHF) region.

The 7586 is not simply an ordinary receiving triode in a small package. RCA describes an all-ceramic-and-metal structure with cantilever-supported cylindrical electrodes and its Dark Heater construction. Siemens identifies long service life, resistance to vibration and shock, and special cathode characteristics. Philips describes it as a special-quality, shock- and vibration-resistant triode.

Mechanical Construction and Heater

The 7586 uses a metal-shell MT4 Nuvistor envelope with a ceramic-wafer E5-65 five-contact base, requiring a Nuvistor socket. The tube has a coated, indirectly heated cathode and may operate in any mounting position.

The heater accepts AC or DC supply. Siemens additionally documents heater switching endurance, with a minimum of 2,000 on/off cycles under its stated test conditions.

Amplifier and Oscillator Applications

The 7586 is intended for low-noise voltage amplification, industrial signal amplification, and stable oscillator circuits, including frequencies in the UHF region. The manufacturer descriptions emphasize stable performance and tight tolerances in demanding equipment.

Siemens publishes an approximately 4 dB noise figure at 200 MHz under noise-matched conditions. This is a defined measurement rather than a universal noise figure across all operating frequencies.

Electrical Characteristics

RCA and Philips document several Class A1 operating points:

The published values are consistent with the triode relationship μ ≈ gₘ × rₚ. The nominal amplification factor around 35 places the tube in the medium-mu category.

The industrial tolerance data include 9–12.5 mA plate current, 10–13 mA/V transconductance, and 28–42 amplification factor under specified acceptance conditions.

Maximum Industrial Ratings

The 330 V supply allowance is not an unrestricted 330 V operating plate voltage. Grid-circuit resistance ratings also depend on metal-shell temperature; RCA supplies a dedicated temperature-dependent rating chart.

Interelectrode Capacitances

The capacitances contribute to input loading and feedback in high-frequency circuits. Siemens publishes its own capacitance definitions and tolerance values, which should be compared under matching measurement conditions.

Industrial Reliability and Special-Quality Testing

The 7586 has unusually extensive manufacturer test documentation. RCA specifies 1,000 g peak-impact shock testing, 2.5 g fatigue vibration for 48 hours at 60 Hz, variable-frequency vibration-noise tests, low-pressure breakdown tests, electrical insulation tests, and production-life testing.

The vibration-noise limits include 25 mV RMS over 3–6 kHz and 500 mV over 6–15 kHz under the prescribed test arrangement, with separate post-stress acceptance limits.

RCA documents early-hour stabilization testing, 100-hour survival testing, 1,000-hour intermittent-conduction testing, and 1,000-hour standby-life testing. These are qualification procedures and should not be interpreted as a single guaranteed service-life figure.

Siemens separately describes service life exceeding 10,000 hours under its quality specification and provides reliability and insulation requirements. Philips emphasizes special-quality shock and vibration resistance.

Related Type 8393

RCA identifies the 8393 as a related medium-mu industrial Nuvistor triode. The two are described as corresponding types differing in heater ratings and interelectrode capacitances.

They must not be substituted without considering their heater and capacitance differences.

Technical Summary

The 7586 is a 6.3 V / 135 mA medium-mu industrial Nuvistor triode with approximately 35 amplification factor, 11.5 mA/V transconductance, and 3 kΩ plate resistance at a principal Class A1 operating point.

Its defining qualities are low-noise UHF-capable amplification, oscillator stability, compact metal-ceramic construction, controlled electrical tolerances, and extensive shock, vibration, insulation, and life testing. The 7586 is particularly suited to critical industrial equipment requiring small size and dependable performance.