Voltage Pentode or Tetrode (with diode) ·Diode-Diode-Pentode
Receiving tube combining radio signal detection or control-voltage rectification with associated voltage amplification. Its detector function is integral to receiver signal processing and supports classification within the radio detector/converter family.
The BRIMAR 6B8SG is a double-diode vari-mu pentode with a 6.3 V, 0.3 A heater and published pentode characteristics at 250 V anode voltage.
International Octal
General specifications
Properties common to every published source and operating point.
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
3 physical sections, each with unique specifications.
Section 1
No fixed ratings are recorded for this section.
First physical diode of Brimar 6B8SG (6G8G) double-diode variable-mu pentode for receiver rectification, detection and AVC. Brimar confirms two diodes but printed section-specific diode maxima are absent in the attached sheet; no diode maximum electrical ratings invented. Distinct physical diode element retained.
Section 2
Brimar 6B8SG, marked equivalent to 6G8G, double-diode variable-mu pentode for receiver AVC and amplification. Typical operating conditions: heater 6.3 V 0.3 A; anode 250 V, screen grid 100 V, control grid -3 V, anode current 6.5 mA, screen current 1.4 mA, mutual conductance 1.0 mA/V (0.001 S), anode impedance 0.8 MΩ. Additional control-grid bias approximately -40 V reduces gm to 0.005 mA/V. These are typical characteristics, NOT absolute maxima. Two physical diode sections distinct; previous gm and rp retained.
Section 3
No fixed ratings are recorded for this section.
Second physical diode of Brimar 6B8SG/6G8G double-diode variable-mu pentode, used for detector/AVC receiver functions. Separate physical diode confirmed; no independently published diode electrical maxima available in this attached manual extract, so no unsupported ratings promoted.
Source-dependent data
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.
Data set 01
Published operating points and test conditions from this source.
Anode Voltage
250 V
Anode Current
6.5 mA
Screen Voltage
100 V
Screen Current
1.4 mA
Control Grid Voltage
-3 V
Control Grid Voltage for Low Transconductance
-40 V
Transconductance=0.005mA/V