WhitakerAudio AM/FM Stereo Tuner 2012, Assembly & User Manual, Page: 124 / 166

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– With the same setup as before, switch the tuner on and adjust the bottom slug for
maximum indication, keeping this indication near –4 V. A generator output voltage of
approximately 5 mV rms should produce –4 V on the AVC bus.
– Switch the tuner off. Remove any connection to the antenna. Leave the 10 k
Ω
resistor
installed for now.
– Connect the signal generator ground to chassis and the signal lead to the terminal of C3a
(the section of the tuning capacitor closest to the PWB) through the 0.01
μ
F capacitor. Use
the TP pad adjacent to the pin. Set the generator to 1600 kHz; confirm with a frequency
counter, if available. Set the output to approximately 1 mV rms.
– Set the AM tuner dial to 1600 kHz.
– Switch the tuner on.
– Fine-tune the AM tuner dial to maximize the AVC reading.
– Adjust the C10 oscillator trimmer for maximum indication on the voltmeter. C10 is the
trimmer adjacent to the middle section of C3 (C3c).
– Set the generator and tuner to 1400 kHz and rock the tuner dial to find the maximum
response. Adjust the C8 mixer trimmer for maximum indication. C8 is the trimmer
adjacent to section C3b, the tuning capacitor section nearest the front panel. This
adjustment typically is quite broad.
– Set both the generator and tuner dials to 650 kHz and adjust the oscillator coil L1 slug for
a peak. Note that if the oscillator coil is off substantially, find the peak using the front
panel tuning dial and then “walk” the L1 adjustment down toward 650 kHz.
– Adjust the mixer coil T2 slug for peak.
– Repeat this procedure as many times as necessary until no further improvement can be
obtained and the oscillator tracks properly with the dial calibration. When repeating the
calibration adjustment, rock the receiver dial for maximum response before adjusting the
mixer coil and trimmer. Oscillator coil adjustments should be repeated only often enough
to bring the receiver into proper calibration. The mixer is then tracked to the oscillator. A