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6CW4

High-mu Nuvistor triode used as a grounded-cathode neutralized VHF RF amplifier in television and FM tuners.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: 12AQ
Socket code: NUVISTOR5
Base pins: 5
Nominal heater: 6.3 V / 135 mA

Description

6CW4 — High-Mu Nuvistor VHF RF Amplifier Triode

An indirectly heated metal-shell Nuvistor for neutralized grounded-cathode amplification in television and FM receiver tuners.

Overview

The 6CW4 is a high-mu Nuvistor receiving triode designed for grounded-cathode, neutralized VHF radio-frequency amplifier stages. RCA specifies its use in the VHF tuners of color and black-and-white television receivers and FM receivers. Its compact metal-shell construction, relatively high transconductance, and low interelectrode capacitances are documented in detailed manufacturer data.

The 2CW4 and 13CW4 are explicitly identified as electrically corresponding variants with different heater ratings. The 6CW4 uses the familiar 6.3 V heater, drawing 0.135 A, rather than the lower-voltage or higher-voltage heaters of those related types.

Construction, Base, and Mechanical Form

The 6CW4 is a single indirectly heated triode with a coated unipotential cathode, grid, and plate in a compact MT4 metal-shell Nuvistor package. RCA identifies a medium ceramic-wafer five-contact Nuvistor base, JEDEC E5-65, with 12AQ basing. It requires a dedicated Nuvistor socket, not a standard noval miniature socket.

RCA's detailed HB3 documentation lists 0.800 inch maximum overall length, 0.625 inch maximum seated length, and 0.440 inch maximum diameter. The tube may be mounted in any position.

The detailed basing sheet assigns the plate to pin 2, grid to pin 4, cathode to pin 8, and heater to pins 10 and 12 in the manufacturer's indexed Nuvistor diagram. Other positions are marked do not use; the shortened pin and large index lug are significant for correct socket orientation.

Heater and Cathode

Heater parameter	Value
Nominal voltage	6.3 V
Nominal current	0.135 A
Calculated heater power	0.851 W
Supply	AC or DC
Maximum peak heater-cathode voltage	±100 V

RCA's detailed heater rating specifies 6.3 ± 0.6 V under its stated design-maximum convention. Sylvania's condensed table rounds the current to 130 mA, while RCA gives 135 mA.

The low heater power is consistent with the compact receiving-tuner role for which the tube is specified.

VHF Neutralized RF Amplifier Service

The manufacturer's intended circuit is a grounded-cathode RF amplifier. The grid is the input electrode and the plate circuit provides the output. In VHF applications, feedback through the small grid-to-plate capacitance can influence gain and stability; the specified neutralized circuit arrangement is intended to compensate for unwanted input-output coupling.

RCA explicitly includes both monochrome and color television tuner service, as well as FM receiver front ends. The manufacturer data describe a specialized receiving RF amplifier, not an audio power-output or transmitter tube.

Electrical Characteristics

RCA supplies both a characteristic test condition and a representative operating condition:

Characteristic	Characteristic point	Operating example
Plate supply voltage	110 V	70 V
Cathode resistor	130 Ω	—
Grid resistor	—	47 kΩ
Plate current	7.0 mA	7.2 mA
Transconductance	9,800 µmhos	12,500 µmhos
Plate resistance	6,600 Ω	5,440 Ω
Amplification factor	65	68

The tube is therefore a high-mu triode with amplification factor approximately 65–68 and transconductance approximately 9.8–12.5 mA/V at the published operating points.

These characteristics are consistent with μ ≈ gₘ × rₚ: 0.0098 S × 6,600 Ω ≈ 65, and 0.0125 S × 5,440 Ω ≈ 68.

RCA also specifies approximately −4 V grid voltage at 10 µA plate current under the stated measurement condition.

Maximum Ratings and Plate-Circuit Resistance

The RCA design-maximum data include:

Rating	Value
Maximum plate voltage	135 V
Maximum plate-supply voltage, conditional	300 V
Maximum cathode current	15 mA
Maximum negative grid voltage	55 V
Maximum peak positive grid voltage	0 V
Maximum plate dissipation	1.5 W, under stated conditions
Maximum fixed-bias grid-circuit resistance	0.5 MΩ
Maximum cathode-bias grid-circuit resistance	2.2 MΩ

The detailed RCA HB3 data clarify that 1.5 W maximum plate dissipation applies with at least 5,000 Ω series plate-circuit resistance; for smaller series resistance, the manufacturer directs the designer to a plate-dissipation rating chart.

RCA permits a 300 V plate supply only with appropriate plate-circuit resistance and operating conditions that prevent the actual plate voltage and dissipation from exceeding their stated limits.

Sylvania lists a 1.0 W plate-dissipation maximum in its family table. This difference should be retained as a manufacturer-specific rating rather than automatically replaced by RCA's higher conditional figure.

The RCA rating applies at metal-shell temperatures up to 135°C.

Interelectrode Capacitances

The approximate direct capacitances are:

Measurement	Value
Grid to plate	0.92 pF
Grid to cathode, heater, and shell	4.3 pF
Plate to cathode, heater, and shell	1.8 pF
Plate to cathode	0.18 pF
Heater to cathode	1.6 pF in RCA data

Sylvania's shielded table gives approximately 1.3 pF heater-to-cathode capacitance. Measurement definitions and manufacturer context should be preserved when comparing the values.

These small capacitances are important in VHF tuned amplifiers, particularly the grid-to-plate capacitance associated with neutralization.

Plate Curves and Thermal Considerations

The six-page RCA HB3 sheet includes average plate characteristics, transfer characteristics, mechanical drawings, and a plate-dissipation-versus-series-resistance rating chart. These expand on the brief receiving-manual table and show why plate supply voltage, actual electrode voltage, and series resistance must be treated separately.

The metal-shell temperature limit is another important distinction from ordinary glass receiving tubes. Thermal conditions must be considered when installing the 6CW4 in compact tuner assemblies.

Related Heater Variants

Type	Heater voltage	Heater current
2CW4	2.1 V	0.450 A
6CW4	6.3 V	0.135 A
13CW4	13.5 V	0.060 A

RCA explicitly identifies the three CW4 types as having corresponding electrical characteristics except for their heater ratings. Their heater circuits are therefore not directly interchangeable without considering the supply.

Technical Summary

The 6CW4 is a 6.3 V / 135 mA high-mu Nuvistor triode for neutralized grounded-cathode VHF RF amplification in television and FM tuners. It provides approximately 65–68 amplification factor, 9.8–12.5 mA/V transconductance, 5.44–6.6 kΩ plate resistance, and about 7 mA plate current at its published operating points.

Its compact metal-shell construction, 12AQ Nuvistor basing, low interelectrode capacitances, and detailed conditional plate-dissipation limits characterize a specialized receiving front-end RF amplifier rather than a general-purpose audio triode.

Socket description

Nuvistor 5-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: 12AQ
Socket code: NUVISTOR5
Base pins: 5
Nominal heater voltage: 6.3 V
Nominal heater current: 135 mA
Parallel heater voltage: -
Parallel heater current: -
Series capable: No

12AQ - 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

Triode

X-ray radiationInterelectrode capacitances

Plate resistance: 6600 Ω
Transconductance: 0.0098 S
Amplification factor: 65
Max plate voltage: 135 V
Max screen voltage: 130 V
Max plate dissipation: 1.5 W
Max cathode current: 15 mA

Published promoted values applied where applicable; additional ratings and operating data retained as parameters.

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

1971 RCA HB3 Binder 4 of 7

Published operating points and test conditions from this source.

SECTION 1

Triode

Characteristics

1 Voltage (AC or DC) — published value 1
1 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
1 Voltage (AC or DC) — published value 2
6.3 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
1 Voltage (AC or DC) — published value 3
0.6 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Current at heater volts = 6.3 — published value 1
6.3 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Current at heater volts = 6.3 — published value 2
0 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Current at heater volts = 6.3 — published value 3
135 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Grid'to plate
0.92 pF
Published datasheet value; multiple values represent separate source-table limits or conditions.
Grid to cathode, shell, and heater
4.3 pF
Published datasheet value; multiple values represent separate source-table limits or conditions.
Plate to cathode, shell, and heater
1.8 pF
Published datasheet value; multiple values represent separate source-table limits or conditions.
Plate to cathode
0.18 pF
Published datasheet value; multiple values represent separate source-table limits or conditions.
Heater to cathode
1.6 pF
Published datasheet value; multiple values represent separate source-table limits or conditions.
Plate Supply Voltage
110 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Grid Supply Voltage
0 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Cathode Resistor
130 ohm
Published datasheet value; multiple values represent separate source-table limits or conditions.
Plate Resistance (Approx )
6600 ohm
Published datasheet value; multiple values represent separate source-table limits or conditions.
Transconductance
9800
Published datasheet value; multiple values represent separate source-table limits or conditions.
Plate Current
7 mA
Published datasheet value; multiple values represent separate source-table limits or conditions.
Grid Voltage (Approx.) for plate µa = 10 — published value 1
10 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Grid Voltage (Approx.) for plate µa = 10 — published value 2
-4 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Pin 2 -Plate
2
Published datasheet value; multiple values represent separate source-table limits or conditions.
Pin 4 -Grid
4
Published datasheet value; multiple values represent separate source-table limits or conditions.
Pin 10 -Heater
10
Published datasheet value; multiple values represent separate source-table limits or conditions.
Pin 12 -Heater
12
Published datasheet value; multiple values represent separate source-table limits or conditions.
Plate Voltage
70 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Grid Resistor
47000 ohm
Published datasheet value; multiple values represent separate source-table limits or conditions.
Plate Resistance (Approx )
5440 ohm
Published datasheet value; multiple values represent separate source-table limits or conditions.
Transconductance
12500
Published datasheet value; multiple values represent separate source-table limits or conditions.
Plate Current
7.2 mA
Published datasheet value; multiple values represent separate source-table limits or conditions.
voltage of 300 volts may be used pro vl ded sufficient
300 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
at the plate of the tube to 135 volts under condl lions of ma.imun~rated
135 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
plate dissipation (1.5 watts)
1.5 W
Published datasheet value; multiple values represent separate source-table limits or conditions.

Other

respect to cathode
100 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
PLATE SUPPLY VOLTAGE
300 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
PLATE VOLTAGE
135 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Negative-bias value
55 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
Peak-positive value
0 V
Published datasheet value; multiple values represent separate source-table limits or conditions.
CATHODE CURRENT
15 mA
Published datasheet value; multiple values represent separate source-table limits or conditions.
resistance of 5000 ohms — published value 1
5000 mA
Published datasheet value; multiple values represent separate source-table limits or conditions.
resistance of 5000 ohms — published value 2
1.5 mA
Published datasheet value; multiple values represent separate source-table limits or conditions.
For fixed-bias operation
0.5 mA
Published datasheet value; multiple values represent separate source-table limits or conditions.
For cathode-bias operation
2.2 mA
Published datasheet value; multiple values represent separate source-table limits or conditions.

Data set 02

1975 RCA RC30

Published operating points and test conditions from this source.

SECTION 1

Triode

Other

Heater Warm-up Time (Average)
8 s
Other
Peak Heater-Cathode Voltage
100 V
Other;PublishedValue1
Peak Heater-Cathode Voltage
100 V
Other;PublishedValue2
Peak Heater-Cathode Voltage
100 V
Other;PublishedValue3
Plate Supply Voltage
300 V
MaximumRating
Plate Voltage
135 V
MaximumRating
Negative-bias value
55 V
MaximumRating
Peak positive value
0 V
MaximumRating
Cathode Current
15 mA
MaximumRating
Plate Dissipation
1.5 W
MaximumRating
Plate Supply Voltage
110 V
TypicalOperation;PublishedValue1
Plate Supply Voltage
70 V
TypicalOperation;PublishedValue2
Cathode-Bias Resistor
130 V
TypicalOperation;PublishedValue1
Cathode-Bias Resistor
0 V
TypicalOperation;PublishedValue2
Grid Resistor —
4 ohm
TypicalOperation;PublishedValue1
Grid Resistor —
0 ohm
TypicalOperation;PublishedValue2
Plate Resistance (Approx.)
6600 ohm
TypicalOperation;PublishedValue1
Plate Resistance (Approx.)
5440 ohm
TypicalOperation;PublishedValue2
Plate Current
7 mA
TypicalOperation;PublishedValue1
Plate Current
7.2 mA
TypicalOperation;PublishedValue2
Grid Voltage (Approx,) for plate current of
10 V
TypicalOperation;PublishedValue1
Grid Voltage (Approx,) for plate current of
-4 V
TypicalOperation;PublishedValue2
For fixed-bias operation
0.5 megohm
MaximumCircuitValue
For cathode-bias operation
2.2 megohm
MaximumCircuitValue
* A plate supply voltage of
300 V
MaximumCircuitValue
in the plate circuit to limit the plate dissipation to
1.5 W
MaximumCircuitValue
PLATE
92 V
MaximumCircuitValue;PublishedValue1
PLATE
524 V
MaximumCircuitValue;PublishedValue2
Maximum Plate Voltage
135 V
Section1
Maximum Plate Dissipation
1.5 W
Section1
Maximum Cathode Current
15 mA
Section1

Capacitance

Grid to Plate
0.92 pF
Capacitance
Grid to Cathode. Heater, and Shell
4.3 pF
Capacitance
Plate to Cathode, Heater, and Shell
1.8 pF
Capacitance
Plate to Cathode
0.18 pF
Capacitance
Heater to Cathode
1.6 pF
Capacitance

Characteristic

Plate Resistance
6600 ohm
Section1
Transconductance
9800 uS
Section1
Amplification Factor
65
Section1