Voltage Drop (typical)Tube Voltage Drop (derived at Ib=155 mA DC)18V
Notes
Tentative data — the 12D4 was introduced by RCA in 1959 for TV damper service.
The 12D4A is a different-rating variant (per TDSL); verify suitability before substitution.
Pin 2 is an internal connection — do not use as a tie point.
Socket terminals 1, 3, and 6 should not be used as tie points.
Base designation 4CG (per GE Essential Characteristics and RCA datasheet).
Heater negative with respect to cathode: 4400V max. Heater positive with respect to cathode: 300V max.
Peak inverse plate voltage rating of 4400V applies when duty cycle of voltage pulse does not exceed 15% of one horizontal scanning cycle (525-line, 30-frame system).
DC component of plate voltage must not exceed 900V. DC component of heater-cathode voltage must not exceed 100V.
Tube voltage drop (Vdrop) is not stated as a discrete figure in the RCA datasheet. Derived from the Average Plate Characteristic curve (92CS-9757, Ef=12.6V) at the maximum DC plate current of 155 mA, where plate voltage reads approximately 18 V.
Pin Layout — Octal
1Same as Pin 10 (Shell)
2Internal Connection
3Cathode
4
Socket-Compatible Tubes ⚠ Not electrically compatible