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Section IV
. Paragraphs
4-49 to 4-59
4-49. The current limiter,
A8Q8,
and A8R22 provide
protection for the series regulator,
Q3.
If the output
becomes shorted, the voltage drop across A8R22 turns
on A8Q8.
The negative
signal from the collector
of
A8Q8 iscoupledthroughthe driver A8Q7 to the series
regulator
Q3, tending
to turn it off.
Output current
is thus limitedto onlythat required to keep A8Q8 con-
ducting.
4-50. +15 VOLT SUPPLY.
The+15 volt supply is sim-
ilar to the -12. 6v supply except that changes in the
output are applied tothe base of A8Q6 and inverted be- `
fore being coupled through A8Q4 tothe series regula-
tor, A8Q2.
4-51.
PLUG.IN
POWER.
: 4-52. Table 4-1 lists the current available from each
power supply for use by the vertical and horizontal
plug-ins.
Users
desiring to design special purpose
circuits
should not exceed the capabilities shown in
'the table.
Thereisno
minimum
current
requirement
'for any supply.
Table 4-1.
LVPS Current Capabilities
Power
Supply
l
Maximum
Safe
-
Current Available
{
+100 VDC
+15 VDC
-12.6 VDC
-100 VDC
4-53.
CALIBRATOR.
4-54. The calibrator circuit performs a dual function--
it provides a 1kHz output signal of 10v pk-pk, +1% for
calibration purposes,
and a lkHz, -100v signal for
. the storage pulse circuit (see Figure 8-15),
A1Q6 and
A1lQ7 areusedina free-running multivibrator circuit.
Diodes A1CR12 and A1CR14 provide voltage protection
to the transistors.
The collector of A1Q
is discon-
HV
OSCILLATOR
35KHZ
HV
XFMR
+100V
REGULATOR
l
'
E HV ADJUST
Model 181A/AR.
nectedfrom A1C15 by AIC R13 as A1Q7 turns off, pro-
vidinga faster pulse rise-time. AlL2andA1C 16 isolate
the multivibrator from the -100v supply, while A1R31
and A1C17
isolate
it from the «15v supply.
The 10v
square wave output is applied to a front-panel connec-
tor foruse inprobe compensation and sensitivity cali-
'bration,
and the -100v square
wave
output from the
collector of A1Q6 is applied to the pulse circuit.
4-55.
OUTPUT
ISOLATION
AMPLIFIERS.
4-56. Signals derivedfrom the Horizontal Plug-In are
coupled to rear panel BNC connectors J5-8 (refer to
Figure 8-7).
Four
emitter
followers,
A2Q1-4,
are
employed
as isolation amplifiers.
The signals actu-
ally developedare determined by the Horizontal Plug-
Inusedinthe
instrument;
hence,
the signals available
can
be determined by referring to the Operating and
Service Manual for the applicable plug-in.
4-57.
HIGH
VOLTAGE
POWER
SUPPLY. (HVPS).
4-58. Three
regulated
voltages
are
produced by the
HVPS:
-1440v,
+7kv,
and a control grid voltage
of
-1450v to- 1500v (refer to Figure 4- T).
A regulated
oscillator isusedto develop the required high voltages
in transformer A5T1.
The -1440v supply is sampled
to provide control of the osc illator output and thus reg-
ulate all three voltages.
4-59. Unregulated
+23v from the LVPS aroeiies pri-
mary power to oscillator Q5 operating at approximately
35kHz (see Figure 8-18).
The outputs from the high
voltage transformer A5 T1 are coupledtotwo-half wave
rectifier/filter circuits and to a voltage tripler/filter
circuit.
CRT control grid voltage is rectified
by
ASCR1
and filtered..
Thé write gun cathode voltage
is rectified by ASCR2 while A5R2
establishes the dc
potential applied to its control grid.
Voltage regula-
tors,
A1V1i and A1V2,
limit the maximum
potential
difference between the control grid and the cathode to
140v.
The
CRT
focus
voltage is obtained from
the
-1440 cathode voltage by a voltage divider network of '
which R5, the FOCUS
control,
is a part. Resistor,
VOLTAGE
TRIPLER
:
RECTIFIER
& FILTER
RECTIFIER M
=~l470V
& FILTER
RECTIFIER
& FILTER
BIA
Bi
Figure 4-7.
HVPS Block Diagram.
4-6
02612-1
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