6189

The 6189 is a medium-mu miniature twin triode used for voltage amplification and in circuits where mechanical ruggedness matters. Tung-Sol markets its 6189/12AU7WA as a special-quality tube: its two sections, with separate cathodes, can perform different functions in the same circuit. Its sheet lists audio amplification, phase inversion, oscillators, and multivibrators, as well as use in industrial and airborne equipment exposed to shock and vibration.

The heater is indirect and has a center tap. Connected in parallel it requires 6.3 V at 300 mA; in series it requires 12.6 V at 150 mA. On the nine-pin Noval base, pins 4 and 5 are the heater ends and pin 9 is the center tap. The two triodes use pins 1-2-3 and 6-7-8 respectively for plate, grid, and cathode. Choose the heater connection from the actual equipment wiring, not just the designation printed on the glass.

A 1968 special-quality sheet gives, for each section, a nominal operating point with 100 V on the plate and 0 V on the grid: 11.8 mA plate current, 3.2 mA/V transconductance, amplification factor 19.5, and 6.25 kΩ plate resistance. At 250 V on the plate and −8.5 V on the grid it instead gives 10.5 mA, 2.2 mA/V, factor 17, and 7.7 kΩ. These are two separate measurement conditions; the current from the first must not be combined with the resistance from the second to describe one operating point.

Special quality also concerns testing and tolerances. The 1968 sheet subjects production samples to a 1,000-hour life test and describes shock tests up to 500 g and vibration tests at 2.5 g and 50 Hz. It explicitly says these mechanical tests are not normal operating conditions. Mazda Belvu presents its 6189 as shock-resistant for mobile equipment and specifies at least 5,000 heater on-off cycles: this is a specification from its own sheet, not a service life in hours guaranteed for every 6189.

A January 1963 JEDEC correction replaces the 6189 registration data with the statement that the type is the same as the 12AU7. The original table listed 300 V and 2.75 W per plate, but the correction means it should not be treated as a separate specification still in force. A later 1968 special-quality sheet gives 330 V and 3 W as absolute maxima for its 6189. The JEDEC type statement thus coexists with selected commercial versions such as Tung-Sol's 6189/12AU7WA, without transferring every special guarantee from one maker to another. For replacement, use the sheet for the actual tube and check the socket, heater, and circuit bias.