Service manual

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PIF VCO Adjustment

Note: Be sure to perform the PIF VCO adjustment whenever the VCO coil (L205) is replaced.

Measuring equipment: Spectrum analyzer, search coil

The method how to manufacture the search coil

Setting the spectrum analyzer

Center frequency: 45.75 MHz

Reference: 60 dBµV/ Should be determined by the amplitude of waveform

Span: 10 MHz

Marker: Set the markers so that the peak marker function can be used.

Adjustment method

1. Allow 30 minutes or more of aging time of this set.

2. When an antenna is connected to the antenna terminal, remove an antenna.

3. Connect pin-5 of IC301 to ground using a wire.

4. Connect the search coil that is locally manufactured to a spectrum analyzer. Move the tip of the spectrum analyzer to L205.

5. Adjust L205 so that the peak is positioned at 45.75 MHz±50 kHz on a spectrum analyzer.

Note 1: Be careful that the search coil does not touch the VCO coil or its leads.

Note 2: Take reading of the spectrum analyzer value when the adjustment screwdriver is removed from the VCO coil.

Note 3: Press the marker peak key of a spectrum analyzer. Read the value when the marker peak key is pressed and adjust the

value for 45.75 MHz. The value cannot be read again even if the marker peak key is pressed until the cursor completes a

full scan of tracing over the waveform on a spectrum analyzer display.

(The value can be read only once during one scan. The value remains the same even if the marker peak key is pressed

before the scan is completed.)

Simplified adjustment procedure

Input signal: Color bars (RF)

Measuring equipment: Pattern generator

Adjustment point: Adjustment menu PAGE 1-5, L205

Adjustment method: Select the adjustment menu PAGE 1-5 "RF VCO". Set the RF VCO value to 58. Adjust L205 so that the

normal color bar picture and the message AFT OK appear on display. When doing this, adjust L205 for the

center of AFT OK lock-in range as close to the center as possible.