Tube cross-reference
2D21 alternatives, equivalents, and replacements
Review exact electrical variations and directional substitutions recorded for the 2D21 specialized - thyratron. Compare core specifications and verify every restriction before using a replacement.
Exact variations of 2D21
These designations belong to the same electrical variation group. Their names may differ because of international standards, manufacturing tolerances, or materials, but they are recorded as electrically equivalent—not merely substitutes.
PL21 NEW (being researched)
- Base
- Not recorded
- Socket
- Not recorded
- Base pins
- Not recorded
- Sections
- 1
- Heater voltage
- Not recorded
- Heater current
- Not recorded
Replacement tubes for 2D21
The following tubes are recorded as possible replacements for 2D21. This direction does not establish that 2D21 can replace them.
Specialized - Thyratron
The database records 2D21W as a possible replacement for2D21.
No special restrictions are recorded for this substitution.
| Specification | Original tube | Replacement |
|---|---|---|
| Tube type | Specialized - Thyratron | Specialized - Thyratron |
| Construction | Thyratron | Thyratron |
| Base | B7G | Not recorded |
| Socket | B7G | IO |
| Base pins | 7 | 7 |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | 0.6 A |
Specialized - Thyratron
The database records 5727 as a possible replacement for2D21.
No special restrictions are recorded for this substitution.
| Specification | Original tube | Replacement |
|---|---|---|
| Tube type | Specialized - Thyratron | Specialized - Thyratron |
| Construction | Thyratron | Thyratron |
| Base | B7G | E7-1 |
| Socket | B7G | B9A |
| Base pins | 7 | 9 |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | 0.6 A |
Specialized - Thyratron
The database records 20A3 as a possible replacement for2D21.
No special restrictions are recorded for this substitution.
| Specification | Original tube | Replacement |
|---|---|---|
| Tube type | Specialized - Thyratron | Specialized - Thyratron |
| Construction | Thyratron | Tetrode |
| Base | B7G | Not recorded |
| Socket | B7G | Not recorded |
| Base pins | 7 | Not recorded |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | 0.6 A |
Specialized - Thyratron
The database records EN91 as a possible replacement for2D21.
No special restrictions are recorded for this substitution.
| Specification | Original tube | Replacement |
|---|---|---|
| Tube type | Specialized - Thyratron | Specialized - Thyratron |
| Construction | Thyratron | Thyratron |
| Base | B7G | Not recorded |
| Socket | B7G | B7G |
| Base pins | 7 | Not recorded |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | 0.6 A |
Specialized - Thyratron
The database records M8204 as a possible replacement for2D21.
No special restrictions are recorded for this substitution.
| Specification | Original tube | Replacement |
|---|---|---|
| Tube type | Specialized - Thyratron | Specialized - Thyratron |
| Construction | Thyratron | Thyratron |
| Base | B7G | Not recorded |
| Socket | B7G | B7G |
| Base pins | 7 | 7 |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | Not recorded |
Where 2D21 can be used as the replacement
In these recorded relationships, 2D21 is the replacement tube. The listed original tubes are not automatically suitable as replacements for 2D21.
Specialized - Thyratron
The database records 2D21 as a possible replacement for20A3.
No special restrictions are recorded for this substitution.
| Specification | 2D21 replacement | Original tube |
|---|---|---|
| Tube type | Specialized - Thyratron | Specialized - Thyratron |
| Construction | Thyratron | Tetrode |
| Base | B7G | Not recorded |
| Socket | B7G | Not recorded |
| Base pins | 7 | Not recorded |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | 0.6 A |
Specialized - Thyratron
The database records 2D21 as a possible replacement for4G280K.
No special restrictions are recorded for this substitution.
| Specification | 2D21 replacement | Original tube |
|---|---|---|
| Tube type | Specialized - Thyratron | Specialized - Thyratron |
| Construction | Thyratron | Thyratron |
| Base | B7G | B7G |
| Socket | B7G | B7G |
| Base pins | 7 | 7 |
| Sections | 1 | 1 |
| Heater voltage | 6.3 V | 6.3 V |
| Heater current | 0.6 A | 0.6 A |
Specialized - Thyratron
The database records 2D21 as a possible replacement forEN91.
No special restrictions are recorded for this substitution.
| Specification | 2D21 replacement | Original tube |
|---|---|---|
| Tube type | Specialized - Thyratron | Specialized - Thyratron |
| Construction | Thyratron | Thyratron |
| Base | B7G | Not recorded |
| Socket | B7G | B7G |
| Base pins | 7 | Not recorded |
| 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 2D21 specifications →