Philips LC4.3E Service Manual page 22

EN 22 5. LC4.3E AA
5.7.4 Video Processing
No Power
1. Check +12 V and 3V3 at position 1J02.
2. If no supply, check the connector 1J02.
3. If it is correct, check the power supply board.
Power Supply is Correct, but no Green LED
1. Check if the connectors 1K00 are properly inserted.
2. If they are inserted correctly, check if the 3V3 is present.
No Picture Display (blank screen with correct sound
output)
1. Check whether the user menu is visible.
2. If the user menu is OK, activate teletext mode.
3. If teletext is OK, the problem is in the ADC (B18) &
Columbus 3D combfilter (B19), if present (depending on
model, see also paragraph "Teletext Path" in chapter 9).
4. If the user menu is not visible, check if the LCD panel
backlight is ON.
5. If the backlight is OFF, the problem is in the power supply
board or LCD panel. Also check pin 12 (LAMP_ON_OFF)
of 1J02. It should be HIGH during normal operation.
Note: For faultfinding purposes, it is important to know the
following: in Pixel Plus and Digital Crystal Clear models, which
have an ADC (B18) and Columbus 3D combfilter (B19), the
digital input of the scaler is used for the digital video path
(Hercules output), whereas the analogue RGB input (analogue
input of the scaler) is only used for teletext. This means that no
mixed mode (video plus teletext simultaneously) is possible. If
there is sound and teletext, but no video and user menu (blank
screen), the digital path (Hercules - ADC - Columbus - Scaler)
is faulty. If there is sound but no teletext, the back-end part
(Scaler - LCD panel) is faulty. In Crystal Clear models, which
do not have an ADC and Columbus, the RGB path (analogue
input of scaler) is used for both video and teletext.
No TV, but PC is Present
1. Check if Hsync_SDTV and Vsync_SDTV are present at pin
1 & pin13 of 7E03.
2. If they are present, check teletext output.
3. If there is no teletext output, the IC TDA150xx may be
defect.
5.7.5 Power Supply
Check Fuse
The power supply (various models are used) contains one fuse
near the AC input connector X002.
1. Check with power supply in "off" state by means of ohmic
measurement.
2. Fuse X102 may open in case of severe lightning strikes
and/or failures in the power supply.
3. Check the standby signal at pin 10 of X200. ON is HIGH,
OFF is LOW. During standby mode only the 3V3 is present
at pin 10.
Protections Concept on Power Supply Board (two models)
1. 12 V output (pin 8 of X200): Short-circuit protected by 2.5
A fuse X610. Over-voltage protection when output voltage
is more than 40% above nominal value.
2. Vaudio output (+18 or +24 V, depending on power
supply model used); (pin 1 of X200): Short-circuit proof
(+18 V version has 2.5 A fuse X660). Over voltage
protection when output voltage is more than 40% above
nominal value.
3. 3V3STBY output (pin 3&4 of X200): Short-circuit proof
with auto-restart. Over voltage protection when output
voltage is more than 40% above nominal value.
Service Modes, Error Codes, and Fault Finding
4. 24 V output (for inverter X520 & X530): Short-circuit
proof with auto-restart. Over voltage protection when
output voltage is more than 40% above nominal value.
Standby Mode
1. Apply a 12 ohm load resistor of sufficient power rating to all
outputs mentioned above (+12 V, +18/ 24 V, +3V3 and +24
V). Connect the STBY pin (pin 10 of X200) to logical "L"
(low), i.e. to GND.
2. Over an input voltage range of 90 V
+3V3 STBY output shall be up.
Normal Mode:
1. Apply a 12 ohm load resistor of sufficient power rating to all
outputs mentioned above (+12 V, +18/ 24 V, +3V3 and +24
V). Connect the STBY pin (pin 10 of X200) to logical "H"
(high), i.e. to the +3V3 STBY output via a 2,2 k pull up
resistor.
2. Over an input voltage range of 90 V
outputs shall be up. The voltage on the +3V3 STBY output
shall be 3.3 V over the entire input voltage range. The
voltage on the big 400 V capacitor on the power supply
should also be 400 V ±10%.
to 276 V only the
AC AC
to 276 V all
AC AC