We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
THEORY AND WIRING OF AMPLIFIERS 565
and in Figures 114 and 115. The positive d. c. lead is the one that connects to the filaments of the rectifying tubes, which in this case is the wire that runs upward from the mid-tap, terminal 5-T, of the right-hand secondary of the filament transformer. The negative terminal is the one that connects with the mid-tap of the plate or high-voltage secondary, the wire joined to terminal 3-T of the secondary of transformer T-5.
Tracing this supply circuit from positive to negative, we may begin at 5-T, the mid-point of the filament transformer secondary, and follow the wire upward to choke coil L-2. From either side of this choke coil its associated filter condensers, C-6, C-7, C-8, C-9, C-10 and C-l-1 are wired across to the negative side of the line, in a normal brute-force filter arrangement, such as we saw in Figure 115. Continuing upward from L-2, the line runs through another choke coil, L-l, to the mid-point of the primary winding of the output transformer. Through that winding to the plates of V-3 and V-4. From the filaments of those tubes to the left-hand secondary of the filament transformer, T-4. From the centertap of that winding up, left and up to the left-hand or positive side of the bias resistor, R-18. From the righthand, or negative side of that resistor down at a slight angle, left, down and left to the key switch, K-2. As that switch appears in the drawing, this circuit is closed through its two left-hand contacts, and continues down, right, up, right, and down to the mid-tap (3-T) of the plate transformer secondary, its negative terminal.
When the position of switch K-2 is changed, the two central prongs are spread apart and make contact with the upper arrowheads, while the lower arrowheads are < ยป] >en-circuited. Then the circuit we have just been tracing runs upward through the right-hand central prong, through the right-hand upper arrowhead, down and through the milliammeter, and thence down, right, up, right, and down to the center tap of the plate transformer secondary. With the switch in this position the meter reads the plate current through tubes V-3 and V-4.
To trace the plate circuit of the other two tubes, we