Marantz 2275 - SERVICING PROCEDURES AND TEST EQUIPMENT; Test Equipment Requirements; AM Alignment Procedures

TEST EQUIPMENT REQUIRED FOR SERVICING
Table 1 lists the test equipment required for servicing the Model 2275 Receiver.
Item
Manufacturer and Model No.
oe
Use
AM Signal Generator
Signal source for AM alignment.
Test Loop
—+
Used with AM Signal generator.
FM Signal Generator
Less than 0.2% distortion
Signal source for FM alignment.
Stereo Modulator
Less than 0.2% distortion
ate . .
Stereo separation alignment and
trouble shooting.
Frequency Counter
MPX Oscillator adjustment
(VCO).
Audio Oscillator
a!
Weston Model CVO-100P, less
than 0.02% residual distortion
is required.
Sinewave and squarewave sig-
nal source.
Oscilloscope
High sensitivity with DC hori-
zontal and vertical amplifiers.
Waveform analysis and trouble
shooting, and ASO alignment.
VTVM
With AC, DC range RF type
VTVM Circuit Tester
AC Wattmeter
Simpson, Model 390
AC Ammeter i
Line Voltmeter
Commercial Grade (1-10A)
Commercial Grade (0-150VAC)
Variable Autotransformer
(0-140VAC, 10 amps.)
Powerstat, Model 116B
Voltage measurements.
Trouble Shooting.
Monitors primary power to
Amplifier.
Monitors amplifier output un
der short circuit condition.
Monitors potential of primary
power to amplifier.
Adjusts level of primary power
to amplifier.
Shorting Plug
Use phono plug with 600 ohm
across center pin and shell.
4
Shorts amplifier input to elimi-
nate noise pickup.
Output Load
(8 ohms, 1%, 100W)
Commercial Grade
Provides 8-ohm load for ampli-
fier output termination.
Output Load
(4 ohms, +1%, 100W)
Commercial Grade
Provides 4-ohm load for ampli-
fier output termination.
Table 1. Test Equipment Required for Servicing
10. AM ALIGNMENT PROCEDURES
10.1 AM IF Alignment
Connect a sweep generator to J153 and an alignment scope to the test point © .
2. Rotate each core of IF transformer L153 for maximum height and flat top symmetrical
1.
response.
10.2 AM Frequency Range and Tracking Alignment
Set AM signal generator to 515kHz. Turn the tuning capacitor fully closed (place the tuning
pointer at the low end.) and adjust the oscillator coi! L152 for maximum audio output.
Set the signal generator to 1650kHz. Place the tuning pointer in the high frequency end
and adjust the oscillator trimmer on the oscillator section of the tuning capacitor for
1.
2.
maximum audio output.
Repeat Step 1 and 2 until no further adjustment is necessary.