Philips HTB5540D/94, Service Manual

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5-1 Trouble shooting Chart
VFD No display on Front Control Board
VFD No display on
Front Control Board
Go
Yes
Refer to CON501 on Power Board
No
Check whether U6 and U10 work good
or not? And fix it or replace the main
board.
No
Replace MCU U8 on Main Board, or
replace the Main Board
No
Check the XP9 ON Front Control Board,
signals at Pin14, 15, 16 arrive the IC U135
PIN6, 8, 9
No
Yes
Yes
Yes
Correct connection
No
Yes
Replace U135 or VFD
Check every supply voltage on Main Board
whether normal or not.
(XP4 PIN4&PIN5:+12V)
Check voltage -24V on main Board at XP9
PIN16: -24V
Check the power key, open/closed key,
source key and other key whether work
normally or not
Check Front Control Board signals at XP9
Pin14 VFD_CLK, Pin15 VFD_DATA, Pin16
VFD_STB
Check whether bad solder exists on XP9 on
Front Control Board and U135 or VFD
Yes