12D4

Rectifier — Octal

RCA

Known Equivalents & Substitutes

12D4A

Similar Tubes (Not Drop-In Compatible)

17D4

Same half-wave TV damper rectifier family but 16.8V heater — not pin-compatible without heater string redesign

25D4

Same half-wave TV damper rectifier family but 25V heater — not pin-compatible without heater string redesign

6AX4GTB

Half-wave TV damper rectifier but 6.3V heater, Octal base — different base and heater voltage

Identical electrically but 6.3V heater — not a drop-in replacement in TV series heater string circuits

Electrical Specifications

Absolute Maximum

Anode Dissipation (max)Plate Dissipation (max)5.5W

Heater-to-Cathode Voltage (max)Peak Heater-Cathode Voltage (heater negative)4,400V

Rectifier

Peak Inverse VoltagePeak Inverse Plate Voltage4,400V

DC Output Current (max)DC Plate Current (max)155mA

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.

Pin Layout — Octal

1Same as Pin 10 (Shell)

2Internal Connection

3Cathode

Socket-Compatible Tubes ⚠ Not electrically compatible

References

Peak Anode Current (surge)Peak Plate Current900mA

Heater

Heater VoltageHeater Voltage12.6V

Heater CurrentHeater Current0.6A

No Connection

5Plate

6No Connection

7Heater

8Heater