Tube cross-reference
KD21 alternatives, equivalents, and replacements
Review exact electrical variations and directional substitutions recorded for the KD21 voltage regulator. Compare core specifications and verify every restriction before using a replacement.
Replacement tubes for KD21
The following tubes are recorded as possible replacements for KD21. This direction does not establish that KD21 can replace them.
Voltage Regulator
The database records 0A3 as a possible replacement forKD21.
No special restrictions are recorded for this substitution.
| Specification | Original tube | Replacement |
|---|---|---|
| Tube type | Voltage Regulator | Voltage Regulator |
| Construction | VoltageRegulator | VoltageRegulator |
| Base | Not recorded | 4AJ |
| Socket | Not recorded | IO |
| Base pins | Not recorded | 8 |
| Sections | 1 | 1 |
| Heater voltage | Not recorded | Not recorded |
| Heater current | Not recorded | Not recorded |
Where KD21 can be used as the replacement
In these recorded relationships, KD21 is the replacement tube. The listed original tubes are not automatically suitable as replacements for KD21.
Voltage Regulator
The database records KD21 as a possible replacement for0A3.
No special restrictions are recorded for this substitution.
| Specification | KD21 replacement | Original tube |
|---|---|---|
| Tube type | Voltage Regulator | Voltage Regulator |
| Construction | VoltageRegulator | VoltageRegulator |
| Base | Not recorded | 4AJ |
| Socket | Not recorded | IO |
| Base pins | Not recorded | 8 |
| Sections | 1 | 1 |
| Heater voltage | Not recorded | Not recorded |
| Heater current | Not recorded | Not recorded |
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 KD21 specifications →