Philips L04HU Service Manual page 15

Blank Screen
Check Vg2
Ok
(fine tune)
Not Ok
Check Beam Current Limit
(voltage is 1.8V-2V when
Not Ok
brightness and contrast is
set to the maximum
Ok
Check heater voltage
(measure pin 9&10
at the CRT socket)
Check video supply
(2457) is approximately
180V
Ok
Figure 5-8 Fault finding tree "Blank screen"
5.8.4
Source Selection
Set is not able to go into AV or any missing AV is
encountered
E.g. AV1 is available but not able to enter to AV1: Check if the
option setting is correct.
Set is able to go to AV, but no audio is heard.
1. Check that continuity of signal is there from the SCART/
Cinch input to the input of the Hercules.
2. If continuity is there and still no audio, check that option
settings are correct.
3. If logic setting is correct and still no audio, proceed to Audio
Decoder/Processor troubleshooting section.
Set is able to go into AV but no video is available:
1. Check continuity from AV input to HERCULES depending
on the input.
2. If continuity is available and yet no video, proceed to Video
Processor troubleshooting section.
Service Modes, Error Codes, and Fault Finding
Picture
appears?
Picture not appearing
Check deflection
circuit
Ok
Picture not appearing
Not Ok
Picture
appears?
Ok
End
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L04HU AA
5.8.5
Tuner and IF
No Picture
1. Check that the Option settings are correct.
2. If correct, check that supply voltages are there.
3. If supply voltages are present, check whether picture is
present in AV.
4. If picture is present in AV, check with the scope the Tuner
IF output signal by manual storage to a known channel.
5. If IF output is present, Tuner is working fine. If no IF output,
I2C data lines may be open, check continuity of I2C lines.
If I2C lines are ok, Tuner may be defect, replaced Tuner.
6. If Tuner IF is present and yet still no picture in RF mode, go
to Video Processing troubleshooting section.
No Picture, No Sound
No Picture,
No Sound,
Raster Ok
Check AGC
Voltage, pin 1
of tuner
Yes
AGC voltage
changes with
different signal
strength
No
Check AGC
circuit section
Figure 5-9 Fault finding tree "No picture, no sound"
5. EN 15
Check tuning
supply voltage,
pin 9 of tuner
Check
>30V & <35V V Supply
No
T
Section
Check supply
voltage, pin 7 of
tuner
Check Power
5V No
Supply
Yes
Check Tuner
pin 4 & 5
I 2 C Bus
Check other
Ok No
functional area
Yes
Replace Tuner
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