Model 120B Section IV
Paragraphs 4-33 to 4-40
AC +I9 VOLT DC + 19 VOLTS DC
b REGULATED TO AMPLIFIERS
POWER SUPPLY VI,V2 AND VlOl
2)
T
- +99VOLTS DC
-
115/230 VOLTS
60 CPS S301 +420,*300,+ 100 TRANSFORMER +300 VOLTS DC
IPHASE -- AND199 VOLTS T302
I - OC REGULATED +I00 VOLTS DC
I
I POWER SUPPLY +420VOLTS DC UNREG
TO AMPLIFIERS,
t
SWEEP CIRCUITS,
6.3 VOLTS AC AND HIGH-VOLTAGE
POWER SUPPLY
-150-VOLT DC
-150 VOLTS DC
b REGULATED
POWER SUPPLY
BD-M-268
Yigure 4-5. Low-Voltage Power Supply, Block Diagram
4-33. One section of the BEAM FINDER switch is in tor C325A. The resulting dc voltage is regulated and
the cathode circuit of V102. When pressed, the switch further by tubes V309, V310, and V311.
increases the common cathode resistance and so re-
duces the gain of the stage that no amount of unbalance
4-38. The circuit functions as follows: when power
ahead of V102 can deflect the sweep off the crt.
is applied (assuming - the 150-volt supply has been ad-
justed properly) the cathode of V310 becomes fixed at
4-34. LOW-VOLTAGE POWER SUPPLY. -65 volts and the grid assumes a slightly more nega-
tive value. If a line voltage surge or load current
4-3 5. BLOCK-DIAGRAM DESCRIPTION. (See figure change were to occur, tending to lower the supply
4-5.) The 115/230-volt, single-phase power is ap- voltage, V310 grid potential would tend to change by
plied through switch S301 to transformer T302. The half the amount, since the grid is tied to a voltage
transformer applies 6.3 volts ac to the vertical am- divider between -150 volts and ground. The result
plifier, horizontal amplifier, sweep generator, and is increased bias for V310, lowering its current,
high-voltage power for supply use as filament voltage; raising its plate voltage, which, in turn, lowers the
the transformer applies also appropriate ac voltages bias on V309. This bias change in V309 lowers its
to the following: the +19-volt d-c regulated power resistance, decreasing the voltage drop across this
supply; the +300-, +loo-, and +99-volt dc regulated element which tends to return the supply voltage ,to
power supply; and the -150-volt dc regulated power its original value.
supply.
4-39. +300-. +loo- AND +99-VOLT DC REGULATED
POWER SUPPLY. The +300-volt supply (figure 5-9)
4-36. The regulated power supplies deliver their dc
operates in almost exactly the same manner as the
outputs to the following circuits: + 19 volts dc is
- 150-volt supply except that it uses the - 150-volt sup-
applied to the horizontal and vertical amplifiers; and
ply as its voltage reference. In this supply, CR301,
'I9, + loo, +300, and are to the
CR302, V307, and V308 are the rectifier, series reg-
vertical amplifier, the horizontal amplifier, the hor-
ulator, and amplifier, respectively. The +loo- and
izontal sweep circuits, and the high-voltage power
+99-volt supply is further regulated by V308B, ref-
supply; in addition, the -150-volt supply applies aneg-
erenced to the +300-volt supply.
ative voltage - to the +19-. +99-. +loo-. and +300-volt
supplies for use as a control voltage. '
4-40. +19-VOLT DC REGULATED POWER SUPPLY.
4-37. -150-VOLT DC REGULATED POWER SUP- (See figure 5-9. ) The +19-volt supply (for the fila-
PLY. The -150-volt supply (figure 5-91 in the 120B ments of vertical amplifiersvland V2) uses rectifier
is used as a reference supply for the +300-, +loo-, CR304 and capacitor C328 for rectifier and filter.
and +99-volt supplies; therefore, any change in the Transistor Q301 is a series regulator using the poten-
-150 volt supply is reflected as a change inthese sup- tial across Zener diode CR302 for its voltage refer-
ply voltages. The ac voltage from T302 is rectified ence. The current in transistor Q301 determines the
and partially filtered by rectifier CR303 and capaci- value of the dc voltage across the filaments. |
ACEC
HEWLETT-PACKARD
