Samsung PL-42P7HP Service Manual page 40

6-2-2 When the unit is repeatedly turned on and off
Symptom - The SMPS relay is repeatedly turned on and off.
In general, the SMPS relay repeatedly turns on and off by the protection function due to a defect on a board connected to the
SMPS.
- Disconnect all cables from the SMPS, operate the SMPS alone and check if the SMPS works properly and if each voltage
Major Checklist output is correct.
- If the symptom continues even when SMPS is operated alone, replace the SMPS.
- If the symptom is not observed when operating the SMPS alone, find any defective ASSYs by connecting the cables one by
one.
Troubleshooting
Does the symptom continue after
Procedures
When separating and connecting the cables such as CN809 of the Main SMPS, CN1, CN2, CN3, CN4 and CN5 of DC-DC
Caution SMPS, CN of the X Main Board, and CN of the Y Main Board, a spark may be generated by the electric charge of the high
capacity capacitor. Therefore, wait some time after separating the power cord from the unit.
Samsung Electronics
No
connecting the power and
removing the CN809 cable from
the Main SMPS?
Yes
Does the symptom continue
after connecting the power and
removing the CN804-2 cable
from the Main SMPS?
Yes
Replace the Main SMPS
Does the symptom continue when
connecting the power after connecting
the CN809 cable and removing the
CN1, CN2, CN4 and CN6 cables
from the DC-DC SMPS?
Does the symptom continue when
connecting the power after
removing the CN4 cable from the
DC-DC SMPS?
Does the symptom continue when
connecting the power after removing
CN2 from the DC-DC SMPS?
Does the symptom continue when
connecting the power after removing
CN810 from the Main SMPS?
Troubleshooting
Replace the
DC-DC SMPS
Replace the
X Main Board
Replace the
Y Main Board
Replace the
Logic Board
6-3