Sony service manual FDL-PT222 Section Circuit Adjustments, T1 Board Adjustment

3-1.A BOARD ADJUSTMENT

[+4.5V ALIGNMENT (RV601)]

Using a digital voltmeter measuring the voltage between JL32 (+4.5V) and JL33 (GND). Adjust RV601 to obtain the value shown below.

Standard Value = 4.45V± 0.05VDC

S601 position = UHF position

[+30.0V CHECK]

Check the voltage across JL29 (+30.0V) and JL33 (GND) .

Standard Value = 30.5V± 1.5VDC

[AUDIO OUTPUT CHECK]

[VIF.AFT COARSE ADJUSTMNT (T201, T202)]

[SETUP]

1.Set S601 on the A board to VHF position.

2.Apply no signal to JL18 (RF).

3.Connect a 1 kΩ resistor between JL77 (+4.5V) and JL28 (RF AGC).

4.Apply a sweep signal across JL26 (IF) and JL27(IF GND). (Fig. 3-1)

Note : Set the sweep signal for JL26 to -30±5dBm. Keep the distance to the ATT output JL26 as short as possible.

1.Feed the audio signal 1kHz 100% modulated.

2.Set RV501 to maximum.

3.Connect an oscilloscope between JL23 (SP) and JL15 (SP GND).

4.Check the waveform on the oscilloscope becomes the stan- dard value.

Standard Value = 1.5V-2.8Vp-p

SWEEP

MARKER

GENERATOR

fo=45.75MHz± 5kHz

ATT

75Ω 6dB

Fig. 3-1

0.01∝ F

JL26

3-2.T1 BOARD ADJUSTMENT

- T1 board - (Component side)

T201 T202

RV201

RV002

RV001

[ADJUSTMNT]

1. Connect an oscilloscope between JL72 (VIDEO) and JL71 (A.GND) and apply an external voltage (MGC) to JL26 to obtain a waveform as shown in Fig. 3-2 (make sure not to clip the extremely short portion).Adjust T202 so that the po- sition at 45.75 MHz is the lowest point.

Note : Align JL51 (MGC) external voltage for approximately a 1.0 Vp-p. Make sure that the JL51 (MGC) external voltage does not exceed 4.3VDC.

2.Remove the external voltage (MGC) from JL51.

3.Connect an oscilloscope between JL31 (AFT) and JL30 (D.GND) and make a coarse adjustment of T201 so that wave- form is close to zero at the 45.75 MHz position.

4.Remove the 1 kilohm resistor connected between JL77 (+4.5V) and JL28 (RF AGC).