Samsung PS42P2SBX/XEC, Service Manual

Page: 62 / 192

Circuit Operation Description
5-46 Samsung Electronics
■
42°”SD logic buffer board T/S
Required test equipment : -.Oscilloscope (digital 400 MHz 2 channel or more)
Other equipment : -.DC power supply (5V : 1EA )
-.Multi meter
-.Logic board : 1EA
-.Sub-PCB ASS'Y for JIG: 1 EA
(1) First, perform eye-inspection and short circuit inspection for the power stage of the logic board to
examine. Then, perform the following examinations on the board in order if no problem was found.
(2) If no problem was found in step ®ÿ, connect buffer board as Figure 5 shows, connect sub-PCB for
COF data check and replace 256K EEPROM with Test EERPOM for the logic board to output full-
white pattern.
(3) Supply 5V to the logic board, and check that the LED on the left-top of the board blinks at about 1 sec-
ond interval. If no problem is found, measure the output waveform of sub-PCB, and compare it with
that of normal state.
(4) Check EC1, EC2, EC3, EC4, FC5, FC6, and FC7 in order. You can only examine doubtable waveform
selectively.
(5) Set probe 1 of oscilloscope to trigger signal, and connect it to the TP31 of the logic board.
(6) Set oscilloscope to 2ms/div. After adjusting probe 2 to 5V/div, check output signal zooming important
points.
(7) Appended waveform is for full-white input pattern. Output waveform when each of R, G and B pat-
tern is supplied individually is summarized in the following table.
❈
For short check, it would be better to test waveform in the order of R, G and B pattern.
R0(TP13,TP49), R1(TP16,TP52), G0(TP14,TP50), G1(TP17,TP53),
B0(TP15,TP51), and B1(TP18,TP54) in The JIG Board
(8) After T/S, turn off the power supply, and disconnect the connector. Record the result on the examina-
tion sheet.
Output waveform for the applied pattern
Full-white R G B
The same as the attached waveform
Control signal output of
sub-PCB for COF data check
R, B, G data signal output of
sub-PCB for COF data check
The output wave-
forms of all of the
R, G, B TP’s are the
same as the
attached waveform. The output wave-
forms of all of the
R0, R1 TP’s are the
same as the
attached waveform. The output wave-
forms of all of the
G0, G1 TP’s are the
same as the
attached waveform. The output wave-
forms of all of the
B0, B1 TP’s are the
same as the
attached waveform.