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WhitakerAudio
7.2.1 FM Tuner Alignment
Transformers and coils in the FM tuner will be adjusted in the following steps. Reference to the
top slug indicates that the adjustment is made on the core nearest the bottom plate of the chassis.
The bottom slug is the core nearest the PWB.
– Switch off the tuner.
– Connect the ground lead of the signal generator to the ground lug adjacent to V54.
Connect the hot lead of the signal generator through a 0.01
μ
F, 400 V, capacitor to V54
pin #1. Use the
TP
pad adjacent to the pin.
– Set the generator to produce 10.70 MHz; confirm with a frequency counter (if available).
Set the output level to be about 100 mV rms or less.
– Connect the ground lead of the voltmeter to a convenient point on the chassis. Connect the
meter input lead to the junction of R75/R77/C75 (
Test Point A
). Set the meter to read
negative dc voltage in the neighborhood of 3 V dc.
– Switch the tuner on and allow a minute or so to warm up.
– Adjust the
bottom
slug of
T54
. Reduce the output of the generator to keep the measured
voltage at Test Point A to be about –1.5 V.When properly adjusted, a generator output of
approximately 25 mV rms is typically required on pin 1 of V54 to yield –1.5 V on the
AGC line.
– Remove the meter input lead from Test Point A and connect it to the junction of R70/C77/
R71 (
Test Point B
). Leave ground lead connected to ground.
– Set the meter to a high sensitivity range and adjust the
top slug only
of ratio detector
transformer
T54
for zero output voltage. Move the alignment tool back and forth a few
times to make sure that the meter swings both sides of the zero mark. If not, turn the core
further in or out until a + or – swing can be obtained when the core is moved in either
direction from the zero output point.
– Switch the tuner off and disconnect the hot lead of the signal generator from pin 1 of V54.
– Connect the ground lead of the signal generator to the ground lug adjacent to V53.
Connect the hot lead of the signal generator through a 0.01
μ
F, 400 V, capacitor to V53
Summary of Contents for AM/FM Stereo Tuner 2012
Page 1: ...WhitakerAudio AM FM StereoTuner User and Assembly Manual...
Page 11: ...11 AM FM Stereo Tuner Figure 1 1 Schematic diagram of the AM tuner section...
Page 17: ...17 AM FM Stereo Tuner Figure 1 2 Schematic diagram of the FM tuner section...
Page 34: ...34 WhitakerAudio Figure 3 1 Component layout for the AM tuner PWB...
Page 36: ...36 WhitakerAudio Figure 3 3 Component layout for the FM tuner PWB...
Page 69: ...69 AM FM Stereo Tuner Set the FM tuner board aside it will be used later b...
Page 101: ...101 AM FM Stereo Tuner Figure 5 11 Chassis view of the AM FM Stereo Tuner...
Page 159: ...159 AM FM Stereo Tuner...
Page 160: ...WhitakerAudio AM FM StereoTuner...
