WhitakerAudio AM/FM Stereo Tuner 2012, Assembly & User Manual

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10.9 6U8 Pentode/Triode Tube
The 6U8 is a medium-mu triode and sharp-cutoff pentode tube well suited to use in RF and audio
equipment. The 9-contact pinout is given in Figure 10.17. In phase-splitter circuits, the pentode
unit should drive the triode unit.
Selected tube parameters are listed in Table 10.9.
Table 10.9 Key Parameters of the 6U8
General Characteristics
Heater (ac/dc) 6.3 V, 0.45 A
Heater-cathode voltage
Peak value ±200 V max.
Average value 100 V max.
Direct interelectrode capacitance (approx.), triode unit
Grid to plate 1.8 pF
Grid to cathode, heater, and pentode elements 2.8 pF
Plate to cathode, heater, and pentode elements 1.5 pF
Direct interelectrode capacitance (approx.), pentode unit
Grid #1 to plate 0.01 pF max.
Grid #1 to cathode, heater, grid #2, grid #3, internal shield 5 pF
Plate to cathode, heater, grid #2, grid #3, internal shield 2.6 pF
Direct interelectrode capacitance (approx.), other
Triode cathode to heater 3 pF
Pentode cathode, pentode grid #2, internal shield 3 pF
Pentode grid #1 to triode plate 0.2 pF max.
Pentode plate to triode plate 0.1 pF max.
Class A
1
Amplifier, Maximum Ratings (Design-Maximum Values) Triode Unit Pentode Unit
Plate voltage 330 V 330 V
Grid #2 (screen grid) voltage Figure 10.6
Grid #2 (screen grid) supply voltage 330 V
Grid #1 (control grid) voltage, positive bias value 0 V 0 V
Plate dissipation 2.5 W 3 W
Grid #2 (screen grid) input
For grid # 2 voltages up to 165V 0.55 W
For grid #2 voltages between 165 and 330V Figure 10.4
Characteristics
Plate supply voltage 125 V 125 V
Grid #2 (screen grid) supply voltage 110 V
Grid #1 (control grid) voltage –1 V –1 V
Pt
G1p
G2p
H
Pp
K , G ,
p 3p
Kt
Gt
H Legend:
H = heater
K = cathode, pentode (p) or triode (t)
G = grid (1, 2, 3), pentode (p) or triode (t)
P = plate, pentode (p) or triode (t)
1
2
3
4
5
6
7
8
9
Figure 10.17 Terminal pinout of the 6U8.