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U31 tube: datasheets and technical data
Explore available pinout, electrical data and related types for the U31 vacuum tube.
The U31 is an indirectly heated half-wave rectifier. Marconi describes it for the power supplies of AC or AC/DC receivers using International or Universal Range valves: its approximately 26 V, 0.3 A heater can be included in the corresponding supply chain. The catalogue emphasises the valve's low impedance, intended to limit voltage drop. The June 1953 sheet shows an octal base: anode on pin 5, cathode on 8 and heater on pins 2 and 7.
The sheet specifies limits of 250 V RMS at the input, 710 V peak inverse voltage and 120 mA rectified DC current. It recommends at least 100 Ω in series with the anode lead. In its two examples with 250 V AC input and 120 mA output, the half-wave circuit using one U31 delivers 250 V DC, while a voltage doubler with two U31 valves reaches 500 V DC; these figures refer to the stated circuits and capacitors and are not a guaranteed voltage for every power supply. Marconi permits mounting in any position and requires free air circulation around the bulb.
Tube images
Pinout and connections
Base: K8A - Octal (Int.Octal, IO) , USA 1935 (Codex=K) (8 pin)
| Pin | Function |
|---|---|
| 1 | ic |
| 2 | h |
| 3 | nc |
| 4 | nc |
| 5 | a |
| 6 | nc |
| 7 | h |
| 8 | k |
Electrical data
Filament
- Filament voltage Vh
- 26 V
- Filament current Ih
- 0.3 A
Datasheet PDF
| Language | Pages | Manufacturer | |
|---|---|---|---|
| U31.pdf | en | 1 | Marconi Italiana |
| U31.pdf | en | 2 | Marconi Italiana |
EL84 ECC83 12AX7 EL34 6L6GC 300B KT88 GZ34
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