6JC6A

The 6JC6A is a miniature sharp-cutoff frame-grid pentode designed primarily for IF amplifier stages of color and black-and-white television receivers. RCA’s manual places its use around 40 MHz. General Electric emphasizes no external shield required and a common plate and screen supply. That sheet describes unilateral replacement of 6JC6 by 6JC6A: the A version has higher dissipation ratings, transconductance and current characteristics. This must not become an unconditional two-way equivalence.

The indirect heater operates at 6.3 V, 0.30 A, AC or DC. The typical class A1 point uses plate and screen supplies of 125 V, cathode resistor 56 Ω, suppressor connected to cathode at the socket. Ratings at this point are plate current 14 mA, screen current 3.4 mA, transconductance 16 mA/V; General Electric and RCA’s manual give plate resistance approximately 0.18 MΩ. Approximately −3 V grid voltage reduces plate current to 100 µA: a numerical cutoff criterion, not strictly zero current.

Without external shield, capacitances are input 8.5 pF, output 3 pF, control grid to plate maximum 0.019 pF. Design-maximum plate voltage is 330 V, dissipation 3.1 W. A screen supply rating of 330 V does not permit 0.7 W screen dissipation at every voltage: RCA gives that limit up to screen voltage 165 V and refers above it to the permissible-power chart, also present in the General Electric sheet. Maximum control-grid circuit resistance is 0.25 MΩ with fixed bias or 1 MΩ with cathode bias.

The nine-contact base is Noval B9A, arrangement 9PM: 1 and 3 cathode, 2 control grid, 4 and 5 heater, 6 no internal connection, 7 plate, 8 screen, 9 suppressor and internal shield. The suppressor therefore has its own terminal and must be connected externally to cathode for the quoted typical conditions. Noval shape alone does not imply that connection is internal.

RCA and General Electric drawings give maximum overall length 2.187 inches = 55.5498 mm, seated height 1.937 inches = 49.1998 mm and diameter 22.225 mm. General Electric specifies minimum diameter 19.05 mm. Both distinguish body excluding tip, range 37.3126–42.0624 mm. Bulb T-6½, any mounting position. Documentation: RCA Electronic Components and Devices, 6JC6A Sharp-Cutoff Pentode, October 1966; General Electric, 6JC6-A Product Information, October 1968, charts dated 5 March 1968; RCA Receiving Tube Manual RC-30, 6JC6A entry, pages 316–317.