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Tube Tinker — Electron Tube Database
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Tuning Indicator ·TuningIndicator

DM21

Low-filament-power electronic tuning indicator developed for battery-operated receivers, providing fluorescent visual tuning indication with minimal heater consumption.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
-
Socket code
-
Base pins
-
Nominal heater
1.4 V / 25 mA

Description

Directly heated electronic tuning indicator developed for battery receivers.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
-
Base pins
-
Nominal heater voltage
1.4 V
Nominal heater current
25 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

1 physical section, each with unique specifications.

Section 1

Tuning Indicator

X-ray radiationInterelectrode capacitances
Max plate voltage
135 V
Max screen voltage
135 V

Published electrical data extracted from supplied datasheet.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1999 Philips 0-D

Published operating points and test conditions from this source.

SECTION 1

Tuning Indicator

Other

  • Battery voltage

    120 V

  • Anode series resistance

    2 MOhm

  • Screen current at grid 0 V

    0.25 mA

  • Grid bias at 5 degree shadow

    -4 V

  • Minimum screen voltage

    90 V

  • Minimum filament voltage

    1.1 V

  • Maximum filament voltage

    1.5 V