Philips LC4.2E Service Manual page 17

5.7.4
Video Processing
No power
1. Check +12 V and 3V3 at position 1910.
2. If no supply, check the connector 1910.
3. If it is correct, check the power supply board.
Power supply is correct but no green light
1. Check the two connectors 1005 and 1601, if they are
properly inserted.
2. If they are inserted correctly, check if the 3V3 is present.
No picture display
1. Check the RGB signal.
2. If it is present, check 3-IC7016 (NE555).
3. If it has output, the problem is in SCALER part.
4. Otherwise, check H-out on pin 2 of NE555. If the input
signal of pin2 is present, but no output, the IC is failed.
Note:
•
If the H-out (pin 67) doesn't have signal or the level is low,
check the output of NE555 (pin 3) during start up.
•
If the H-out (pin 67) has a signal (or has a signal for a very
short time), change IC7016 (NE555).
No TV but PC is present
1. Check if HSYNC and VSYNC are present at PIN 3 of 7071
and 7015.
2. If they are present, check RGB output.
3. If there is no RGB output, the IC TDA120xx can be failed.
Comb Filter not working
1. Check the option bit 5 in SAM.
2. Check NVM setting. Address 1229 is 0000.
5.7.5
Power Supply
Check fuses
This power supply contains three fuses. One is near the mains
inlet (marked on the board as 1102) and two other are near the
output connectors (marked 1610 and 1660).
1. Check with power supply in off state by means of ohmic
measurement.
2. Fuse 1102 may open in case of severe lightning strikes
and/or failures in the power supply. Despite the fact, that
this fuse is mounted in a fuse holder and the marking text
on the board, it is not meant to be field replaceable.
3. Fuses 1610 and 1660 may open in case a severe overload
of the 12 V outputs. Replacement of the power supply is
needed, but not before the cause of the overload
conditions is resolved.
Standby mode
1. Apply a 12 ohm load resistor of sufficient power rating to all
outputs (+3 V3, +12 VAL, +12 VL and +24 V). Connect the
STBY pin to GND.
2. Over an input voltage range of 90 V_ac to 264 V_ac only
the +3 V3 output shall be up and within regulation (±5%).
The voltage on the POWER DOWN pin shall be < 0.3 V at
an input voltage below 160 V_ac, and 3.3 V ±10% at an
input voltage higher than 240 V_ac.
Normal mode:
1. Apply a 12 ohm load resistor of sufficient power rating to all
outputs (+3 V3, +12 VAL, +12 VL and +24 V). Connect the
STBY pin to the +3 V3 output.
2. Over an input voltage range of 90 V _ac to 264 V_ac all
outputs shall be up and within regulation (±5%). The
voltage on the POWER DOWN pin shall be 3.3 V ±10%
over the entire input voltage range. Additionally, the
voltage on the big capacitor mounted flat on the PCB shall
be 400 V ±10%
Service Modes, Error Codes, and Fault Finding LC4.2E AA 5. EN 17