SECTION 3 CIRCUIT ADJUSTMENTS
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
[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 k� 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.
[+30.0V CHECK]
Check the voltage across JL29 (+30.0V) and JL33 (GND) . Standard Value = 30.5V±1.5VDC
[AUDIO OUTPUT CHECK]
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 standard value. Standard Value = 1.5V-2.8Vp-p
SWEEP MARKER GENERATOR JL26 fo=45.75MHz±5kHz 75� 6dB 0.01µF
ATT
Fig. 3-1
3-2.T1 BOARD ADJUSTMENT
- T1 board - (Component side)
T201 T202
[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 position 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 waveform 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).
