Figure 4 eh.23. This is a repeat of the graph in Figure 4 eh.5 with different lines drawn on it. If you want to skip this then jump to the next paragraph. This is a graph labeled at the top 6SL7, 12SL7 Average Plate Characteristics. The horizontal axis is labeled plate volts and goes from 0 to 500. The vertical axis is labeled plate milliamps and goes from 0 to 5. There are 7 lines on the graph that start at the bottom and go generally up and to the right. These are grid voltage lines and the one on the left is for a voltage of 0 and the one on the right is for minus 6 volts. The steps are in one volt increments. The first line, E sub G = 0 starts at the origin and for a short distance goes almost straight up. It quickly curves to the right becoming almost straight and making an approximately 30 degree angle with the vertical. It passes through the points. 0, 0. 50, 1. 97, 2. 140, 3. 180, 4. 215,5. The minus 1 curve starts near the bottom and bends to the right. It straightens up and goes up parallel to the 0 curve. The points are, 21, 0.025. 110, 1. 163, 2. 210, 3. 250, 4. 290, 5. The minus 2 E sub G line has more curvature than the one to its left. Its points are, 88, 0. 185, 1. 235, 2. 280, 3. 322, 4. 349, 4.6. The minus 3 line begins at 150, 0.02. 255, 1. 307, 2. 350, 3. 394, 4. The minus 4 line starts at 225, 0 and the rest of the points are, 320, 1. 375, 2. 423, 3. The points for the minus 5 volt line are, 280, 0.02. 390, 1. 445, 2. The minus 6 volt curve has points of, 350, 0.05. 460, 1. 480, 1.25.
There are several lines which have been drawn on the graph. There is a red line that begins at the point 400, 0 and goes up to the left to the point 0, 0.82. The desired operating point is on the load line between the minus 3 and minus 4 volt grid voltage lines. There are points marked at 0.64 and 0.85 mA on the minus 3 and minus 4 lines respectively. A blue line connects these points and it is labeled 4.7 k. There are two more points at 0.54 and 0.72 mA. These points are connected by a magenta line and labeled 5.6 k. There are two final points marked on the lines at 0.44 and 0.59 mA. A blue line connects these points and it is labeled 6.8 k. A green line begins at the point 358, 0 and passes through the point where the red and magenta lines intersect. This point is 264, 0.52. This line goes as far to the left as it can. The green line crosses the minus 3 line at 240 volts and the minus 4 line at 387 volts. End verbal description.
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