Tube cross-reference
21EP4A alternatives, equivalents, and replacements
Review exact electrical variations and directional substitutions recorded for the 21EP4A specialized - cathode ray. Compare core specifications and verify every restriction before using a replacement.
Where 21EP4A can be used as the replacement
In these recorded relationships, 21EP4A is the replacement tube. The listed original tubes are not automatically suitable as replacements for 21EP4A.
Specialized - Cathode Ray
The database records 21EP4A as a possible replacement for21EP4.
No special restrictions are recorded for this substitution.
| Specification | 21EP4A replacement | Original tube |
|---|---|---|
| Tube type | Specialized - Cathode Ray | Specialized - Cathode Ray |
| Construction | CathodeRay | CathodeRay |
| Base | Not recorded | Not recorded |
| Socket | B12D | B12A |
| Base pins | 5 | 5 |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | 0.6 A |
Specialized - Cathode Ray
The database records 21EP4A as a possible replacement for21EP4C.
No special restrictions are recorded for this substitution.
| Specification | 21EP4A replacement | Original tube |
|---|---|---|
| Tube type | Specialized - Cathode Ray | Specialized - Cathode Ray |
| Construction | CathodeRay | CathodeRay |
| Base | Not recorded | 12N |
| Socket | B12D | Not recorded |
| Base pins | 5 | 5 |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | 0.6 A |
Verify before substituting
Matching a base or heater voltage is not enough to prove that two tubes are interchangeable. Check pin connections, heater current, maximum ratings, bias requirements, warm-up behavior, and the equipment manufacturer’s service documentation before making a substitution.
View the complete 21EP4A specifications →