The Sylvania 6SA7GT vacuum tube is an essential electronic component for the restoration of vintage American radios. Designed as a pentagrid converter (heptode), its primary function in a superheterodyne receiver is to perform two operations simultaneously: generate the local oscillator signal and mix it with the incoming radio frequency (RF) signal from the antenna to produce a stable and clean intermediate frequency (IF) for further amplification and detection.

Features of the GT (Glass Tubular) Version
While the original 6SA7 featured a metal envelope for electromagnetic shielding, this 6SA7GT version uses a glass tubular envelope. To preserve signal integrity, Sylvania incorporated an internal cylindrical shield (visible as the dark section inside the glass), providing excellent protection against stray radio-frequency emissions. This design combines effective RF shielding with the classic glass appearance highly valued by vintage radio restorers and collectors.

Authenticity and Condition (New Old Stock)
This tube is a genuine New Old Stock (NOS) component and comes in its original mid-century Sylvania yellow-and-black factory box. It shows no signs of installation or use, preserving its original factory appearance. Although it has not been tested on a tube tester, its pristine condition and original packaging make it an excellent choice for collectors, restorers, and vintage radio enthusiasts seeking authentic period components.

Manufacturer History: Sylvania Electric Products
Sylvania Electric Products was one of the leading American vacuum tube manufacturers throughout the 20th century. Renowned for its rigorous quality standards, Sylvania tubes were widely used in military equipment during World War II and later became a trusted choice for the rapidly growing consumer electronics industry. Today, original Sylvania NOS tubes are highly regarded by collectors and restorers for their quality construction, long service life, and historical authenticity.

Who Is This Tube For?

• Vintage radio restoration technicians working on classic Zenith, Philco, RCA, and Crosley receivers equipped with transformer-powered circuits.

• Analog electronics enthusiasts studying frequency conversion circuits and superheterodyne receiver design.

• Collectors who appreciate authentic vintage components complete with their original factory packaging.

Detailed Technical Specifications (Datasheet)

• Tube Type: Pentagrid Converter (Heptode)

• Base (Socket): Standard 8-Pin Octal (B8G)

• Cathode Type: Indirectly Heated Cathode

• Filament Voltage (Vf): 6.3 V (AC or DC)

• Filament Current (If): 0.3 A (300 mA)

• Maximum Plate Voltage (Va max): 300 V

• Maximum Screen Grid Voltage (Grids 2 and 4): 100 V

• Maximum Plate Dissipation: 1.0 W

• Capacitance (Control Grid to Plate): 0.13 pF (approx.)

(FAQ)

Q: What is the difference between a 6SA7 and this 6SA7GT?
A: Electrically, they are identical and interchangeable. The difference is mainly in their physical construction: the original 6SA7 uses a black metal envelope, while the 6SA7GT features a glass tubular (GT) envelope. This Sylvania GT version incorporates an internal shield to provide protection against unwanted interference, similar to the shielding offered by the metal version.

Q: Can I use this tube as a replacement for a 12SA7 in my “All American Five” radio?
A: No. Although both tubes perform the same function as a pentagrid converter, they are not interchangeable. The 6SA7GT requires a 6.3-volt filament supply, while the 12SA7 requires 12.6 volts and was designed for series-connected heater circuits commonly found in transformerless “All American Five” radios. Installing a 6SA7GT in place of a 12SA7 can result in incorrect heater operation and may damage the tube or the radio circuit.

Q: Has the tube been tested?
A: This tube is strictly NOS (New Old Stock) and has been preserved in its original factory packaging. Due to its pristine unused condition—showing no socket insertion marks on the pins and with the original getter coating intact—it is considered to be in original factory condition. However, it has not been tested on a modern tube tester, so actual emission and electrical performance have not been measured.