In the article we will consider the double triode 6H8C, characteristics and application features. This radio tube is designed for use in ULF. It is installed in ULF pre-amplification stages and phase inverters. The lamp is also used in a variety of impulse structures, TV signal receivers, and measuring equipment. The cathode has an indirect heating of the oxide type. The lamp can work in any position, despite the glass case. The base has a key and 8 pins. The maximum resource is 500 hours.
Electrical data
The characteristics of the 6H8C radio tube are as follows:
- The input/output capacitance of the first triode is 2.8pF/0.8pF.
- The input/output capacitance of the second triode is 3pF/1, 2pF.
- Through capacitances of the first/second triode – 3.8pF/4pF.
It is also necessary to highlight the following parameters of the radio tube:
- Filament voltage is notless than 6.3V but not more than 7V.
- The maximum anode voltage is 250 V.
- Grid Offset – 8V.
- Anode current - 9 mA.
- Glow current - 600 mA.
- Slope - 2.6 mA/V.
- Internal resistance - 7.7 kOhm.
- Max gain is 20.5.
Using as ULF
When designing a ULF preliminary stage, you need to know that when using a low-power anode load, the gain is significantly reduced. In this case, the frequency response is significantly expanded. If the anode voltage is relatively large, then the gain increases, the frequency response of 6H8C becomes narrower.
The capacitor that blocks the resistance in the cathode circuit is best used electrostatic, capacitance in the range of 10…50 uF.
Tone correction from 6Н8С
The radio tube can work in fine correction schemes. In this case, the true gain is only a few units. Potentiometers, which adjust the high and low frequencies, are installed in the grid circuit. With the position of the rotors of variable resistors in the middle position, the characteristic is uniform and lies within 30 Hz - 15 kHz.
It is worth noting that when building circuits, the 6H8C lamp can be replaced by analogues, the dimensions of which are much smaller. Ideal for this purpose 6N2P.
