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Tube Database (7,341 tube types · 1,270 archive entries)

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Tube-number record

U.21

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BrandMazda
ClassHigh Voltage Rectifier
Base4-pin
Filament2 V @ 1850 mA

Construction

Primary TypeRectifier
EnvelopeGlass
SectionsSingle

Filament / Heater

Heater NotesDesigned to provide suitable time delay

Absolute Maximum Ratings

Plate Voltage4500 V
Cathode Current5 mA

Audio Performance

Key Features
  • Indirectly heated
  • Time delay heating
  • High voltage television supply

Typical Operation

ModePlate VGm (µmhos)Rp (Ω)µPlate mA
Rectifier (RMS 3700V)3700 V———0.5 mA
Rectifier (RMS 4000V)4000 V———0.5 mA
Rectifier (RMS 4500V)4500 V———0.5 mA

Application Notes

The U.21 avoids the use of special delay switching and protects the cathode ray tube from excessive voltage stress during heating time.

Datasheets

Datasheet: U21.pdf

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Datasheets courtesy of Frank Philipse via Frank's Electron Tube Data Sheets.

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