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17. TEST
EQUIPMENT
REQUIRED
FOR SERVICING
Table 1 lists the test equipment required for servicing the Model 4270 Receiver.
Item
Manufacturer and Model No.
AM Signal Generator
Signal source for AM align-
ment.
Used
with
AM
Signal
gen-
Test Loop
erator.
FM
Signal
Generator
Less than
0.3%
distorsion.
Signal
source
for FM
align-
ment.
Stereo Modulator
Less than 0.3% distorsion.
Stereo
separation
alignment
and trouble shooting.
Frequency Counter
MPX Oscillator adjustment
(VCO).
saad
Weston Model CVO-100P, less | Sinewave and squarewave sig-
than 0.02% residual distortion | nal source.
is required.
High sensitivity with DC hori-
zontal and vertical amplifiers.
With AC, DC, RF range.
Audio Oscillator
shooting and ASO alignment.
Voltage measurements.
Trouble shooting.
Simpson, Model 390
Monitors primary power to
|
Amplifier.
AC Ammeter
Commercial Grade (1-10A)
Monitors amplifier output un-
der short circuit condition.
Circuit Tester
AC Wattmeter
Line Voltmeter
Commercial Grade
Monitors potential of primary
(0-150V AC)
power to amplifier.
Variable Autotransformer|
Powerstat, Model 116B
(0-140V AC, 10 amps)
Shorting Plug
Adjusts level of primary
power to amplifier.
Use phono
plug with 600
ohm across center pin and
shell.
Output Load
Commercial Grade
Provides 8-ohm load for
(8 ohms, +1% 100W)
amplifier output termination.
Output Load
Commercial Grade
Provides 4-ohm load for
(4 ohms, +1% 100W)
amplifier output termination.
Table 1. Test Equipment Required for Servicing
Shorts amplifier input to
eliminate noise pickup.
18.
AM ALIGNMENT
PROCEDURE
18.1
AM IF Alignment
1.
Connect a sweep generator to the J153 and an alignment scope to the test point ©.
2.
Rotate each core of IF transformer L153 and L154 for maximum height and flat top sym-
9
metrical response.
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