RF.AGC ADJUSTMENT
(1) Input the VHF color bar signal from the test signal generator.
Approx. 1.0Vp
(2) Adjust RV201 to optimum position so that there is no snow
noise on the screen.
CHANNEL DISPLAY POSITION ADJUSTMENT45.75MHz
(1) Set S601 in the VHF position.
Insert resistors (47kW + 15kW ) between JL25 and JL77 (4.5V
line), and short circuit JL21 and JL30 (D.GND).
(2) Receive 2ch, and adjust the channel display position with
RV002.
(3) Receive 13ch, and adjust the display bar with RV004.
(4) Carry out tracking, because (2) and (3) interfere with each other.
(5) Receive 6 and 7ch, and check that the display bar conforms to
the standard.
(6) Set S601 in the UHF position.Fig.3-2
(7) Receive 14ch and adjust the display position with RV001.
(3) Remove the external voltage (MGC) from JL51.
(8) Receive 40ch and 69ch, and check that the display bar con-(4) Connect the output between JL31 (AFT) and JL30 (D.GND) to
forms to the standard.an oscilloscope, and roughly adjust T201 so that the position
of 45.75MHz will be a zero cross.(9) Remove resistors from JL25 and JL77, and open the short cir-
cuit between JL21 and JL30
(5) Remove 1kW from the section between JL77 (4.5V) and JL28
(RF AGC).
JL25
AFT ADJUSTMENT15K
(1) Insert 1kW between JL77 (4.5V) and JL28 (RF AGC).
47K
Note:Because of drifting due to aging, adjustment should
be made at the end of the process.
(2) Switch the sweep signal to CW.JL77
fo = 45.75MHz ? 5kHz
Input the above signal to the section between JL26 (IF) and
JL27 (IF GND), and finely adjust T201 so that the level be-Display bar
tween JL31 (AFT) and JL30 (D.GND) will be 2.2 ? 0.4VDC.
(3) Remove 1kW from the section between JL77 (4.5V) and JL28Channel No.
(RF AGC).6
*Channel No. and display ber are to be in line.
Fig.3-3
� 9 � |
ACEC
