Posté : 31 oct. 2006, 17:22
On prend en compte les dissipations des grilles écran, il me semble 2W pour la EL84 donc on tape plus dans le 14W en fait.
The Zero Bias Grounded Cathode Amplifier.
If the grid of a triode tube is connected to common through a large resistor, say ten million ohms, a negative voltage will build up on the grid. This is caused by electrons impacting on the grid wires and staying there giving the grid a negative charge. The grid wires are small but they are big enough that electrons accidentally run into them. The large resistor causes this charge to leak off very slowly and electrons are continuously hitting the grid so a steady DC voltage exists on the grid. This voltage is enough to bias the tube without a resistor in the cathode. Tubes such as the 12 SQ7 and 12AV6 have been specifically designed to be operated under these conditions. Sometimes this is referred to as "Grid Leak Bias". The voltage is difficult to measure because the input resistance of most DMMs and VTVMs is 10 Meg ohms. The only way to make a valid measurement is to disconnect the resistor and let the meter take its place. The diagram of this type of amplifier is shown below.
The advantage of this circuit is that it has fewer components. The disadvantage is that the designer has less control over the plate current and voltage of the tube.
Si c'est un MI60 t'as pas fini de m'avoir sur le dosBasstyra a écrit :[HS encore...]
Je sais pas encore. Le gars m'a pas dit grand chose de plus.
[/HS]
M'en fou je l'éteins la nuit, nah !Basstyra a écrit :En pleine nuit, ok, j'oublierais pas...
Faut que je retrouve ton tel...
Avec les tensions surtout ! Et puis mesurer les valeurs réelles des résistances, des condensateurs, les impédances du transfo de sortie, noter le layout enfin la base quoi 8)Basstyra a écrit :Je pense que de toute facon, quelque soit le modèle, je prendrais le temps de repiquer le schéma complet...