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бесізоп У
5-60,
POWER
SUPPLY.
5-61,
Check at А1 pin 7 for +6.4 to +7 volts and А1
pin 9 for -6. 4 to -7 volts.
If there is no
output, check
А104 first.
И Ше power
supply has been overloaded,
A1Q4 may be bad.
Minimum battery voltage is 15.5
volts.
Table 5-5.
Power Supply Voltages
NOTE
The voltages listed in this table
are nominal,
Å tolerance of
+10% should be allowed except
for minimum voltages listed.
CHECK POINT
VOLTAGE
Emitter A1Q1
+15V
(+8V min)
Collector
А101
+7. 3V
Base А101
+14, ВУ
(7. 8V min)
Emitter А10)2
+6. ТУ (+6.4V min)
Collector A1Q2
+15V
(8,6У min)
Emitter A1Q3
-0,5У
Collector A1Q3
-0.2V
Across A1CR2
-6.2У
5-63.
DC AMPLIFIER.
5-64.
То make ап operational check oftheDC Ampli-
fier, set the RANGE
switch to 1 and the FUNCTION
switchto+DCV.
Connecta
1 volt sourcetothe VOLTS
and COM terminals and monitor the voltage at A1 pin
8.
Since the DC
Amplifier
is a unity gain amplifier,
the voltage should be +1.07 +0. 07 volts dc.
If this
reading is correct,
the DC Amplifier is operating
properly,
If it is incorrect, proceed with the follow-
ing troubleshooting procedures.
5-65.
Check at the collector
of A1Q9 for +3.5 Vdc,
and check for +3,0 Vdc at AITP1.
If the voltage at
the collector of A1Q9 is quite high (6 or 7 volts) and
the voltage at AITP1 is +3,0 Vdc, А109 is probably
open,
If the collector
voltage is low and the test
point voltage is correct,
А108 is probably
shorted.
If both voltages are incorrect, A1Q7 or A1Q8 is probably
bad.
5-66.
If the collector voltage on A1Q is correct and
the voltage at AITP1 is slightly higher than normal,
A1Q6 is probably bad.
NOTE
И А196 is replaced and the meter
remains pegged or indicates upscale
and cannot be adjusted,
check the
value of factory selected component
А18197 See Paragraph 5-71 and 5-73.
Model 427A
5-67,
AC METERING
CIRCUIT.
5-68.
To check the AC
Metering
Circuit,
set the
RANGE to 0,01 and the FUNCTION to ACV.
Connect
а 10 mV rms
source
to the VOLTS
and COM terminals
and monitor the signal at А2 ріп 0.
The signal at А2
ріп 0 should be 10.7 mV rms
+0.7 mV.
If the
mea-
5-69,
Monitor the signal at the collector
of A2Q3.
The signal should be 0.28 V rms +0. 04 V.
И the
measured signal is correct, the AC Metering Circuit
is functioning properly.
If not,
proceed with the
following troubleshooting procedures.
5-70.
Check for dc voltage levels listed in Table 5-6.
На
given reading is wrong, the trouble
is probably
in that component or its associated circuit.
If A2CR3
or A2CR4
are replaced and the zero offset in АСУ
FUNCTION is ргежег {Вал 2%, check the value of factory
selected component A2R14*, See Paragraph 5-72 and 5-77.
Table 5-6.
AC Metering Circuit Voltages
NOTE
The voltages listed in this table
are nominal.
A tolerance of +10%
Should be allowed.
CHECK POINT
VOLTAGE
А2ТР1
А201 Collector
A2Q2 Emitter
A2Q3 Collector
5-71.
ADJUSTMENT
OF FACTORY
SELECTED
COMPONENTS.
5-72.
Certain components within the Model 427A аге
individually
selected
in order to compensate
for
slightly varying circuit parameters,
These compo-
nents are denoted by an asterisk (%) on the schematic,
and the optimum or average value is shown.
The
following paragraphs describe the function of each
factory selected component and give instructions for
their selection.
Normally these components do not
need to be changed unless another associated compo-
nent is changed,
For example,
replacement of a
transistor may require the changing of an associated
factory selected component.
5-13.
А1Е19%,
5-74.
A1R19* adjusts the range of the АМР BAL re-
sistor A1R15.
И the AMP BAL A1R15 cannot be ad-
justed properly after replacing transistor A1Q6, А1-
R19* may need to be changed.
Use the following steps
to select A1R19*.
а,
Set RANGE
to 0.3.
b.
Set DC 7ЕВО/Я о adjustment to center and
A1R15
to its center.
01791-3
RR —— a.
-
a «а
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