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CURRENT RRCTIFICATIOX
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teriorate with age, resulting in a gradual decrease in current output. A new tube is the only remedy.
"Stack" or "Disc" Current Rectifiers
The stack or disc type rectifier has been in use in small units for a long time. (44) Only recently has it been developed commercially in sizes sufficient to deliver as much as sixty-live amperes. It can now be made to deliver any desired amperage. It deserves our consideration because it is so sturdy and durable. (45) Once installed it requires no care save an occasional dusting and careful inspection every thirty days to make sure its electrical connections are in good order. (46) It makes no bothersome noise, it is free from vibration and has no effect on most types of sound equipment even if located a few feet away.
(47) Fig. 74D is a symbolic illustration of the circuit of a single unit, half-wave rectifier of the stack or disc type. The arrowhead and cross line in the upper line is the conventional symbol for a stack or disc rectifier. So long as the wire on the arrowhead side is positive, the unit will pass current. When, however, the a. c. reverses its direction and that wire becomes negative, current can no longer flow, as will be explained. Fig. 74E is
an assembly of units in the form put out by one manufacturer. Its action is symbolized in Fig. 74D. Current will flow through this unit only during each alternation or half cycle. It is therefore a half-wave rectifier.
(48) In Fig. 74F we see
a circuit representing four
such units, 1, 2, 3 and 4, so
connected that each will pass
current through opposite half
cycles. When the half cycle occurs that causes the upper
wire of the a. c. line to be positive (we are considering the
flow of current from positive to negative — if the direc
Figure 74E