Tube cross-reference
1FD9 alternatives, equivalents, and replacements
Review exact electrical variations and directional substitutions recorded for the 1FD9 voltage pentode or tetrode (with diode). Compare core specifications and verify every restriction before using a replacement.
Replacement tubes for 1FD9
The following tubes are recorded as possible replacements for 1FD9. This direction does not establish that 1FD9 can replace them.
Voltage Pentode or Tetrode (under 100V)
The database records 1S5 as a possible replacement for1FD9.
No special restrictions are recorded for this substitution.
| Specification | Original tube | Replacement |
|---|---|---|
| Tube type | Voltage Pentode or Tetrode (with diode) | Voltage Pentode or Tetrode (under 100V) |
| Construction | Diode-Pentode | Diode-Pentode |
| Base | Not recorded | 6AU |
| Socket | B7G | B7G |
| Base pins | 7 | 7 |
| Sections | 2 | 2 |
| Heater voltage | 1.4 V | 1.4 V |
| Heater current | 0.05 A | 0.05 A |
Where 1FD9 can be used as the replacement
In these recorded relationships, 1FD9 is the replacement tube. The listed original tubes are not automatically suitable as replacements for 1FD9.
Voltage Pentode or Tetrode (under 100V)
The database records 1FD9 as a possible replacement for1S5.
No special restrictions are recorded for this substitution.
| Specification | 1FD9 replacement | Original tube |
|---|---|---|
| Tube type | Voltage Pentode or Tetrode (with diode) | Voltage Pentode or Tetrode (under 100V) |
| Construction | Diode-Pentode | Diode-Pentode |
| Base | Not recorded | 6AU |
| Socket | B7G | B7G |
| Base pins | 7 | 7 |
| Sections | 2 | 2 |
| Heater voltage | 1.4 V | 1.4 V |
| Heater current | 0.05 A | 0.05 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 1FD9 specifications →