EL51 — Power Pentode, B8A | Tubeofile | Tubeofile

EL51

Name: EL51
Brand: Philips

Power Pentode — B8A — Philips

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

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Known Equivalents & Substitutes

No known equivalents. If you know of any, use the ⚑ Report Issue button above.

Similar Tubes (Not Drop-In Compatible)

6550

Similar power class (42W) but Octal beam tetrode — different socket and tube type

807

Similar power class (~30W) and era but 5-pin base with top cap — completely different socket

EL34

Later Philips power pentode (25W), Octal base — lower Pa (25W vs 45W), different socket

EL37

Similar power class (~25W) Mullard pentode but Octal base — not P8A compatible

EL50

Same P8A base and pinout but much lower power (18W vs 45W) — not a safe replacement in EL51 circuits

EL53

Same P8A base family, 6.3V heater — verify pin assignment and power ratings before substituting

KT88

Closest in power class (42W) but Octal beam tetrode — different socket and tube type

Electrical Specifications

Absolute Maximum

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

Screen Voltage (max)Screen Voltage (max operational)750V

Anode Dissipation (max)Anode Dissipation (max)45W

Screen Dissipation (max)Screen Dissipation (max, full drive)25W

Notes

The EL51 is an unusually powerful tube (45W Pa) on the P8A side-contact base — significantly more powerful than the common EL50 (18W) but sharing the same base type and top-cap anode arrangement.
No direct equivalents have been identified across any reference source (Brans Vademecum, Philips interchange, RCA, Sams). The Philips interchange guide lists only 'EL51 = EL51' with no alternatives. This makes the EL51 essentially irreplaceable without circuit modification.
Produced by Philips (Eindhoven), Tesla (Czechoslovakia), and Valvo (Germany). The Tesla production continued well into the 1960s, making Czech-made EL51s the most commonly available today.
Part of the same P8A-base wartime family as the EL50 and EF50, developed for military radar and communications equipment where high power output was needed from compact side-contact tubes.

Pin Layout — B8A

1No Connection

2Heater

3Heater

Socket-Compatible Tubes ⚠ Not electrically compatible

EL50 EL6

References