Zenith XBV243 series Service Manual page 19

TROUBLESHOOTING (CONTINUED)
KEY doesn't work.
(3)
KEY doesn't work.
Is 5V applied to
IC501 Pin 15?
YES
Does LED or FLD change
when a function button is
pressed?
4. OSD CIRCUIT
1) No OSD display.
No OSD display.
Is 5.3V applied to
IC501 Pin 42?
YES
Does oscillation occur at
IC501 Pins 52, 53?
YES
Does oscillation occur at
IC501 Pins 50, 51?
YES
Replace IC501.
2) No F.OSD display.
No F.OSD display.
Refer to "(1) No OSD
display".
YES
Does the C.SYNC signal
appear at IC501 Pin87?
YES
Replace IC501.
VR168 - 923-03485
ELECTRICAL
NO
Refer to "SMPS 5.3VA
Trouble Shooting".
Replace the defective
NO
switches.
NO
Refer to "SMPS 5.3VA
Trouble Shooting".
NO Is the oscillation input to
Q501 base?
Check or Replace the
N O
Peripheral Circuitry. (L506,
R517, C519, C518, R518)
(3) I2C BUS CHECK
The I2C waves don't
come out.
Does Power appear at
the Pull up impedence
(R508, R510)?
YES
N O
Replace IC501.
Refer to "AVCP . C. Sync.
Trouble shooting".
3-7
Check whether X301
oscillates
NO
YES
Check or Replace the
Peripheral Circuitry. (L506,
R517, C519, C518, R518)
NO
Refer to "SMPS 5.3VA
Trouble Shooting".
D35E COMBO - ELECTRICAL