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ALIGNMENT METHOD
FM ALIGNMENTS
NECESSARY INSTRUMENTATION
FM GENERATOR
(less than 0.05% THD)
STEREO GENERATOR
(less than 0.05% THD, more than 50 dB separation at 1 kHz.
AUDIO
GENERATOR
(not necessary if FM generator has built in sweep; i.e. SOUND TECHNOLOGY ST 1000A and
—
$T 1020A)
2 AC VTVM's
(or one with left/right channel switch)
THD ANALYZER
(resolution better than 0.1%)
OSCILLOSCOPE
(5mV or better sensitivity, X input capability)
FREQUENCY COUNTER
|
|
VOM or DMM
(high impedance, must read in mV)
DIODE DETECTOR PROBE
COPPER / FERRITE
INDUCTOR
IMPORTANT
While all FM generator output levels hereafter are referred to the 300 ohm input, 75 ohm input can
be used, but be aware of possible equiprnent groundloops and divide the RF output levei by 2.
Before alignments commence
set input selector to tuner and release tape, mono and dynsep defeat
switches (out)
ALIGNMENT
OF FRONTEND should only be necessary after repair to frontend or crysta! oscillator
circuits (pin 2 and 3 on IC7)
A
TUNING VOLTAGE
(OSCILLATOR)
It is essential to check tuning voltage before aligning the rest of the frontend.
Connect DMM between shield and pin 6 on frontend.
2.
Tune to 108 MHz and adjust L 707 if voltage is incorrect.
SPECIFICATION
20.5V +0.5V
3.
Tune to 87.5 M#z and read voltage, repeat step 2 and 3 if incorrect.
SPECIFICATION
3V+0.5V
B.
RF ADJUSTMENT
(TRACKING)
1.
Connect RF generator to antenna input and detectorprobe to pin 1,1C 2 (IF DETECTOR).
with ground to detectorshield.
Adjust sensitivity of oscilloscope to maximum (5mV or better) and modulate
FM
generator sweep
+ 300
kHz or more
WITH
modulating
(sweep) signal connected to X-imput of
oscilloscope.
Set tuner to 105MHz, enter into preset 2, and tune generator so that curve appears on oscilloscope,
es
IF ADJUSTMENT
—~5-—
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