6973

Basing (pinout)

Bottom view — the socket as you see it from the wiring side. Hover, tap, or focus a pin to name it. Read from the datasheet basing diagram (how to read these →).

Datasheets

Primary manufacturer data, via public tube-data archives. The model below is fitted to the tabulated "average characteristics" in these sheets; the datasheet files themselves are linked, never rehosted.

Circuit Codex model

A CC0 ngspice model in the Koren form, fitted here to the published anchor — no parameters copied from other model collections. Methodology →

Anchor

Va=250 V, Vg2=250 V, Vg1=-15 V → Ia=46 mA, Ig2=3.5 mA, gm=4800 µmho

Source

RCA 6973 data sheet, 10-60 — Characteristics, Class A1 Amplifier

Note

µ=9.479 is SOLVED, not read. Neither the data sheet nor the RCA Receiving Tube Manual RC-30 entry for this tube prints an amplification factor of any kind — no grid-No.1-to-grid-No.2 figure and no triode-connection figure — and µ is the one Koren parameter a single operating point cannot fix, because it only ever appears as Vg2/µ + Vg1. What the sheet does publish is a push-pull fixed-bias table that runs the screen at three different voltages, and those rows measure it. µ is fitted to them by least squares on relative error (pipeline/fit_models.py, solve_pentode_mu) with the Class-A1 anchor above still reproduced exactly, which is what CI gates. EX=1.5 and KVB=30 (pentode) are project defaults per METHODOLOGY.md.

File

models/6973.inc ↗

See these parameters drawn: the load line explorer plots the 6973's plate-curve family from this model and solves an operating point on it.

Maximum ratings

Design-maximum values for push-pull Class AB1 service. Twelve watts of plate dissipation is the number that matters: it is barely more than an EL84's, in a tube asked to make 20 W from a pair, so a 6973 output stage has very little thermal margin and its screen grid — 2 W, and only 330 V — has less. The separate 410 V ceiling applies when the screens are taken from taps on the output transformer primary rather than from their own supply.

Plate voltage

440 V

Grid-No.2 (screen-grid) voltage

330 V

Grid-No.2 input

2 W

Plate dissipation

12 W

Plate and grid-No.2 supply voltage, screens tapped on the OT primary

410 V

Peak heater-cathode voltage

200 V, either polarity

Bulb temperature at the hottest point

250 °C

Grid-No.1 circuit resistance

0.5 MΩ fixed bias · 1 MΩ cathode bias

Rating system

Design maximum — the line no individual valve may cross

Source

RCA 6973 data sheet, 10-60 — Push-Pull AF Power Amplifier, Class AB1, maximum ratings (design-maximum values) ↗