Zenith XBR411 - Osd Circuit

3-10
4. OSD CIRCUIT
(1) I
2
C BUS CHECK
Keys do not work
Is 5V applied to IC501
Pin78?
Does FLD change when
a function button is
pressed?
No I
2
C bus communication
Does Power appear at the
Pull up impedence
(R569, R507)?
Replace IC501.
Refer to “SMPS 5.3VA
Trouble Shooting”.
Replace the defective
switches.
Refer to “SMPS 5.3VA
Trouble Shooting”.
YES
YES
NO
NO
NO
2. SERVO CIRCUIT
(4) Keys do not work
VCR ELECTRICAL TROUBLESHOOTING GUIDE