Repair Tips - Philips 7603 series Service Manual

Protections
If a fault situation is detected an error code will be generated and if necessary the set will be put in the protection mode.
Blinking of the red LED at a frequency of 3 Hz indicates the protection mode. In some error cases the microprocessor does
not put the set in the protection mode. The error codes of the error buffer can be read via the service menu (SAM), the
blinking LED procedure or via ComPair. The DST diagnose functionality will force the set into the Service-standby, which is
similar to the usual standby mode, however the microprocessor has to remain in normal operation completely.
To get a quick diagnosis the chassis has three service modes implemented:
• The Customer Service Mode (CSM).
• The Service Default Mode (SDM). Start-up of the set in a predefined way.
• The Service Alignment Mode (SAM). Adjustment of the set via a menu and with the help of test patterns.
See for a detailed description Circuit description

Repair Tips

Below some failure symptoms are given, followed by a repair tip.
• Set is dead and makes hiccuping sound
'MainSupply' is available. Hiccupping stops when de-soldering L5561, meaning that problem is in the 'MainSupply' line.
No output voltages at LOT, no horizontal deflection. Reason: line transistor 7460 is defective.
• Set is dead, and makes no sound
Check power supply IC 7520. Result: voltage at pins 1, 3, 4, 5 and 6 are about 180 V and pin 8 is 0 V. The reason why
the voltage on these pins is so high is because the output driver (pin 6) has an open load. That is why MOSFET 7521 is
not able to switch. Reason: feedback resistor 3523 is defective. Caution: be careful measuring on the gate of 7521;
circuitry is very high ohmic and can easily be damaged!
• Set is in hiccup mode and shuts down after 8 s.
Blinking LED (set in SDM mode) indicates error 5. As it is unlikely that ?P 'POR' and '+8V protection' happen at the same
time, measure the '+8V'. If this voltage is missing, check transistor 7480.
• Set is non-stop in hiccup mode
Set is in over current mode; check the secondary sensing (opto coupler 7515) and the 'MainSupply' voltage. Signal
'Stdby_con' must be logic low under normal operation conditions and goes to high (3.3 V) under standby and fault
conditions.
• Set turns on, but without picture and sound
The screen shows snow, but OSD and other menus are okay. Blinking LED procedure indicates error 11, so problem is
expected in the tuner (pos. 1000). Check presence of supply voltages. As 'Vlotaux+5V' at pin 5 and 7 are okay,
'VT_supply' at pin 9 is missing.
Conclusion: resistor 3460 is defective.
• Set turns on, but with a half screen at the bottom.
Sound is okay
Blinking LED (set in SDM mode) indicates error 3. Check 'Vlotaux+11V' and '+50V'. If they are okay, problem is expected
in the vertical amplifier IC 7471. Measure with a scope the waveform on pin 17 of the UOC. Measure also at pin 1 of IC
7471. If here the signal is missing, a defective resistor R3244 causes the problem.