KT90

Name: KT90
Brand: EI

Beam Tetrode — Octal — EI

Data: HighHigh quality — base, heater, all universal parameters present, and ≥50% of desirable parameters filled in. Safe to use for design decisions.

↗ TDSL ↗ Radiomuseum

Known Equivalents & Substitutes

65506550AKT88

Electrical Specifications

Section 1 — Beam Tetrode

Absolute Maximum

Anode Voltage (max)Anode Voltage (max)750V

Screen Voltage (max)Screen Voltage (max)650V

Anode Dissipation (max)Anode Dissipation (max)50W

Screen Dissipation (max)Screen Dissipation (max)8W

Notes

The EI datasheet does not provide single-ended load impedance (rl) or single-ended output power (Pout). Only push-pull figures are given: 110 W/pair at Va=550 V, Vg2=400 V; 160 W/pair at Va=750 V, Vg2=600 V.
TDSL lists additional substitutes with different ratings: 6550B, 6550C, CK6550, CV5220, KT88S, KT88SC, SV6550C.
Pin 1 has no connection. Pin 6 has no connection. Pin 8 is cathode tied to beam-forming plates internally.
Vhk_max (heater-to-cathode voltage) is 300 V total DC — higher than many octal power tubes.
Triode-strapped data is from the manufacturer datasheet (EI). Schlangen (2009) independently measured similar values: mu=9.0, gm=15.0 mA/V, rp=700 Ohm at Va=650 V, Ik=600 mA max.

Pin Layout — Octal

1No Connection

2Heater

3Anode

4

Socket-Compatible Tubes ⚠ Not electrically compatible

12AV5 12AX4 12DQ6 12E1 12J5 12J5GT 12W6GT 1H4 25L6GT 350B 367A 5881 6A5G 6C2C 6CD6G

References