Trouble Shooting Chart
No video and sound
Solution:
?
Check the inter-connection between power supply
board and decoder board, CN203 to Con303
?
Check the supply voltage at the output of U204 pin
2 and pin 4.
Solution:
Check C36 C37 L35 L36 and Y1(27MHz crystal)
Solution: Replace Q9
Solution: Replace U7
Solution: Check the reset circuit Q1 R33
R35 R33 R31 D2 Be69
Solution Replace U2 (EEPROM)
No Video, Sound output and
LED display
Check point:
Measure the inter-connection
pin 2 Pin 6 of CON303 on decoder board.
Observe: the +5V and +2.5 supply voltage are
Presented. Board is shot circuit manually.
Check point:
Q9 (Lm117-3.3V) on main board
Observe: the +3v3 at pin3 of Q9
Check point:
Measure pin112 of Ali M3351
Observe: Measure the 27Mhz
oscillation frequency
Check point:
check the collector of Q1
Observe: a 5V is presented
The pin1 of C303 is 2.5V
Observe: N/A
YES
NO
NO
YES
NO
YES
YES
NO
Check points: check the IC U2, U3, U4, U17 on Main board
Observe: is there any short circuit between components
Check points: Measure the output voltage on the address bus of
U7
4-3
NO
YES
Check points:
Pin 6 and pin 5 of U2 on main board.
Observe: The IC clock and data signals
are presented
YES
NO
NO
Pcon waveform
27M wave form
