6CY7

The 6CY7 is a nine-pin miniature dual triode with dissimilar sections, designed to combine the vertical-deflection oscillator and amplifier in television sets. The first section, with a high amplification factor, serves as a blocking oscillator; the second, with a low factor and higher current capability, as the deflection amplifier. This division, described by GE, RCA and Tung-Sol, defines the valve: its triodes are not identical copies whose characteristics can be treated interchangeably.

The heater requires 6.3 V and 0.75 A AC or DC on pins 4 and 5. Section one has plate on 6, grid on 7 and cathode on 8; section two has plate on 1, grid on 3 and cathode on 9. Pin 2 is an internal connection which the sheet says not to use. GE lists the 8CY7 alongside the 6CY7, with different heater ratings, and also attributes controlled warm-up to the 8CY7 for television series heater chains. This characteristic should not automatically be transferred to the 6CY7.

Typical operating points show how different the sections are. The first, at 250 V plate voltage and −3 V grid bias, has plate current 1.2 mA, amplification factor 68, approximately 52 kΩ plate resistance and transconductance 1.3 mA/V. The second, with a 150 V plate supply and 620 Ω cathode resistor, has 30 mA, factor 5, approximately 920 Ω plate resistance and transconductance 5.4 mA/V. Grid-to-plate capacitances also differ: about 1.8 pF for section one and 4.4 pF for section two, without an external shield. Current and transfer curves are published separately, consistent with these different roles.

For vertical service in a 525-line, 30-frame-per-second television system, RCA and GE give Design-Maximum ratings of 350 V plate voltage for both sections and dissipations of 1 W for the oscillator and 5.5 W for the amplifier. The latter has 35 mA average and 120 mA peak cathode-current limits. Its 1,800 V plate-pulse limit applies to pulses no longer than 15% of a vertical scanning cycle, or 2.5 ms under the stated conditions, not to continuous voltage. GE also says that grid-leak bias requires an adequate cathode resistor or another means of protection when excitation is lost. Documentary sources: RCA, GE ET-T1424 and Tung-Sol 6CY7 sheets; RCA Receiving Tube Manual RC-30, page 239.